From 1381b9e0c30cfd3cdeb68fd4d6fe72bd0e3263d5 Mon Sep 17 00:00:00 2001
From: Don Jayamanne <don.jayamanne@outlook.com>
Date: Thu, 15 Sep 2022 08:53:33 +1000
Subject: [PATCH 01/10] Revert "Compress notebook output streams before
 rendering (#160667)"

This reverts commit 4230c22a08a0438af4809d33e4cfd561f714b127.
---
 extensions/ipynb/src/serializers.ts           | 27 ++++----
 extensions/ipynb/src/streamCompressor.ts      | 63 -------------------
 src/vs/workbench/api/common/extHostTypes.ts   |  5 +-
 .../view/renderers/backLayerWebView.ts        | 11 ++--
 .../view/renderers/stdOutErrorPreProcessor.ts | 56 -----------------
 .../contrib/notebook/common/notebookCommon.ts |  8 ---
 6 files changed, 21 insertions(+), 149 deletions(-)
 delete mode 100644 extensions/ipynb/src/streamCompressor.ts
 delete mode 100644 src/vs/workbench/contrib/notebook/browser/view/renderers/stdOutErrorPreProcessor.ts

diff --git a/extensions/ipynb/src/serializers.ts b/extensions/ipynb/src/serializers.ts
index f075737b4d865..4f33b07a1501e 100644
--- a/extensions/ipynb/src/serializers.ts
+++ b/extensions/ipynb/src/serializers.ts
@@ -7,7 +7,6 @@ import type * as nbformat from '@jupyterlab/nbformat';
 import { NotebookCell, NotebookCellData, NotebookCellKind, NotebookCellOutput } from 'vscode';
 import { CellOutputMetadata } from './common';
 import { textMimeTypes } from './deserializers';
-import { compressOutputItemStreams } from './streamCompressor';
 
 const textDecoder = new TextDecoder();
 
@@ -277,17 +276,21 @@ type JupyterOutput =
 
 function convertStreamOutput(output: NotebookCellOutput): JupyterOutput {
 	const outputs: string[] = [];
-	const compressedStream = output.items.length ? new TextDecoder().decode(compressOutputItemStreams(output.items[0].mime, output.items)) : '';
-	// Ensure each line is a separate entry in an array (ending with \n).
-	const lines = compressedStream.split('\n');
-	// If the last item in `outputs` is not empty and the first item in `lines` is not empty, then concate them.
-	// As they are part of the same line.
-	if (outputs.length && lines.length && lines[0].length > 0) {
-		outputs[outputs.length - 1] = `${outputs[outputs.length - 1]}${lines.shift()!}`;
-	}
-	for (const line of lines) {
-		outputs.push(line);
-	}
+	output.items
+		.filter((opit) => opit.mime === CellOutputMimeTypes.stderr || opit.mime === CellOutputMimeTypes.stdout)
+		.map((opit) => textDecoder.decode(opit.data))
+		.forEach(value => {
+			// Ensure each line is a seprate entry in an array (ending with \n).
+			const lines = value.split('\n');
+			// If the last item in `outputs` is not empty and the first item in `lines` is not empty, then concate them.
+			// As they are part of the same line.
+			if (outputs.length && lines.length && lines[0].length > 0) {
+				outputs[outputs.length - 1] = `${outputs[outputs.length - 1]}${lines.shift()!}`;
+			}
+			for (const line of lines) {
+				outputs.push(line);
+			}
+		});
 
 	for (let index = 0; index < (outputs.length - 1); index++) {
 		outputs[index] = `${outputs[index]}\n`;
diff --git a/extensions/ipynb/src/streamCompressor.ts b/extensions/ipynb/src/streamCompressor.ts
deleted file mode 100644
index cea3184e16ce6..0000000000000
--- a/extensions/ipynb/src/streamCompressor.ts
+++ /dev/null
@@ -1,63 +0,0 @@
-/*---------------------------------------------------------------------------------------------
- *  Copyright (c) Microsoft Corporation. All rights reserved.
- *  Licensed under the MIT License. See License.txt in the project root for license information.
- *--------------------------------------------------------------------------------------------*/
-
-import type { NotebookCellOutputItem } from 'vscode';
-
-
-/**
- * Given a stream of individual stdout outputs, this function will return the compressed lines, escaping some of the common terminal escape codes.
- * E.g. some terminal escape codes would result in the previous line getting cleared, such if we had 3 lines and
- * last line contained such a code, then the result string would be just the first two lines.
- */
-export function compressOutputItemStreams(mimeType: string, outputs: NotebookCellOutputItem[]) {
-	// return outputs.find(op => op.mime === mimeType)!.data.buffer;
-
-	const buffers: Uint8Array[] = [];
-	let startAppending = false;
-	// Pick the first set of outputs with the same mime type.
-	for (const output of outputs) {
-		if (output.mime === mimeType) {
-			if ((buffers.length === 0 || startAppending)) {
-				buffers.push(output.data);
-				startAppending = true;
-			}
-		} else if (startAppending) {
-			startAppending = false;
-		}
-	}
-	compressStreamBuffer(buffers);
-	const totalBytes = buffers.reduce((p, c) => p + c.byteLength, 0);
-	const combinedBuffer = new Uint8Array(totalBytes);
-	let offset = 0;
-	for (const buffer of buffers) {
-		combinedBuffer.set(buffer, offset);
-		offset = offset + buffer.byteLength;
-	}
-	return combinedBuffer;
-}
-const MOVE_CURSOR_1_LINE_COMMAND = `${String.fromCharCode(27)}[A`;
-const MOVE_CURSOR_1_LINE_COMMAND_BYTES = MOVE_CURSOR_1_LINE_COMMAND.split('').map(c => c.charCodeAt(0));
-const LINE_FEED = 10;
-function compressStreamBuffer(streams: Uint8Array[]) {
-	streams.forEach((stream, index) => {
-		if (index === 0 || stream.length < MOVE_CURSOR_1_LINE_COMMAND.length) {
-			return;
-		}
-
-		const previousStream = streams[index - 1];
-
-		// Remove the previous line if required.
-		const command = stream.subarray(0, MOVE_CURSOR_1_LINE_COMMAND.length);
-		if (command[0] === MOVE_CURSOR_1_LINE_COMMAND_BYTES[0] && command[1] === MOVE_CURSOR_1_LINE_COMMAND_BYTES[1] && command[2] === MOVE_CURSOR_1_LINE_COMMAND_BYTES[2]) {
-			const lastIndexOfLineFeed = previousStream.lastIndexOf(LINE_FEED);
-			if (lastIndexOfLineFeed === -1) {
-				return;
-			}
-			streams[index - 1] = previousStream.subarray(0, lastIndexOfLineFeed);
-			streams[index] = stream.subarray(MOVE_CURSOR_1_LINE_COMMAND.length);
-		}
-	});
-	return streams;
-}
diff --git a/src/vs/workbench/api/common/extHostTypes.ts b/src/vs/workbench/api/common/extHostTypes.ts
index f7b89d987a907..a717fa90515a1 100644
--- a/src/vs/workbench/api/common/extHostTypes.ts
+++ b/src/vs/workbench/api/common/extHostTypes.ts
@@ -17,7 +17,7 @@ import { IExtensionDescription } from 'vs/platform/extensions/common/extensions'
 import { FileSystemProviderErrorCode, markAsFileSystemProviderError } from 'vs/platform/files/common/files';
 import { RemoteAuthorityResolverErrorCode } from 'vs/platform/remote/common/remoteAuthorityResolver';
 import { IRelativePatternDto } from 'vs/workbench/api/common/extHost.protocol';
-import { CellEditType, ICellPartialMetadataEdit, IDocumentMetadataEdit, isTextStreamMime } from 'vs/workbench/contrib/notebook/common/notebookCommon';
+import { CellEditType, ICellPartialMetadataEdit, IDocumentMetadataEdit } from 'vs/workbench/contrib/notebook/common/notebookCommon';
 import { checkProposedApiEnabled } from 'vs/workbench/services/extensions/common/extensions';
 import type * as vscode from 'vscode';
 
@@ -3545,8 +3545,7 @@ export class NotebookCellOutput {
 		for (let i = 0; i < items.length; i++) {
 			const item = items[i];
 			const normalMime = normalizeMimeType(item.mime);
-			// We can have multiple text stream mime types in the same output.
-			if (!seen.has(normalMime) || isTextStreamMime(normalMime)) {
+			if (!seen.has(normalMime)) {
 				seen.add(normalMime);
 				continue;
 			}
diff --git a/src/vs/workbench/contrib/notebook/browser/view/renderers/backLayerWebView.ts b/src/vs/workbench/contrib/notebook/browser/view/renderers/backLayerWebView.ts
index a32ebc7dc1a93..a7eb492ad43c6 100644
--- a/src/vs/workbench/contrib/notebook/browser/view/renderers/backLayerWebView.ts
+++ b/src/vs/workbench/contrib/notebook/browser/view/renderers/backLayerWebView.ts
@@ -35,7 +35,7 @@ import { NOTEBOOK_WEBVIEW_BOUNDARY } from 'vs/workbench/contrib/notebook/browser
 import { preloadsScriptStr } from 'vs/workbench/contrib/notebook/browser/view/renderers/webviewPreloads';
 import { transformWebviewThemeVars } from 'vs/workbench/contrib/notebook/browser/view/renderers/webviewThemeMapping';
 import { MarkupCellViewModel } from 'vs/workbench/contrib/notebook/browser/viewModel/markupCellViewModel';
-import { CellUri, INotebookRendererInfo, isTextStreamMime, NotebookSetting, RendererMessagingSpec } from 'vs/workbench/contrib/notebook/common/notebookCommon';
+import { CellUri, INotebookRendererInfo, NotebookSetting, RendererMessagingSpec } from 'vs/workbench/contrib/notebook/common/notebookCommon';
 import { INotebookKernel } from 'vs/workbench/contrib/notebook/common/notebookKernelService';
 import { IScopedRendererMessaging } from 'vs/workbench/contrib/notebook/common/notebookRendererMessagingService';
 import { INotebookService } from 'vs/workbench/contrib/notebook/common/notebookService';
@@ -44,7 +44,6 @@ import { WebviewWindowDragMonitor } from 'vs/workbench/contrib/webview/browser/w
 import { IEditorGroupsService } from 'vs/workbench/services/editor/common/editorGroupsService';
 import { IWorkbenchEnvironmentService } from 'vs/workbench/services/environment/common/environmentService';
 import { FromWebviewMessage, IAckOutputHeight, IClickedDataUrlMessage, ICodeBlockHighlightRequest, IContentWidgetTopRequest, IControllerPreload, ICreationContent, ICreationRequestMessage, IFindMatch, IMarkupCellInitialization, RendererMetadata, ToWebviewMessage } from './webviewMessages';
-import { compressOutputItemStreams } from 'vs/workbench/contrib/notebook/browser/view/renderers/stdOutErrorPreProcessor';
 import { DeferredPromise } from 'vs/base/common/async';
 
 export interface ICachedInset<K extends ICommonCellInfo> {
@@ -1277,14 +1276,12 @@ var requirejs = (function() {
 		let updatedContent: ICreationContent | undefined = undefined;
 		if (content.type === RenderOutputType.Extension) {
 			const output = content.source.model;
-			const firstBuffer = isTextStreamMime(content.mimeType) ?
-				compressOutputItemStreams(content.mimeType, output.outputs) :
-				output.outputs.find(op => op.mime === content.mimeType)!.data.buffer;
+			const first = output.outputs.find(op => op.mime === content.mimeType)!;
 			updatedContent = {
 				type: RenderOutputType.Extension,
 				outputId: outputCache.outputId,
-				mimeType: content.mimeType,
-				valueBytes: firstBuffer,
+				mimeType: first.mime,
+				valueBytes: first.data.buffer,
 				metadata: output.metadata,
 			};
 		}
diff --git a/src/vs/workbench/contrib/notebook/browser/view/renderers/stdOutErrorPreProcessor.ts b/src/vs/workbench/contrib/notebook/browser/view/renderers/stdOutErrorPreProcessor.ts
deleted file mode 100644
index 7f20c6316fc1d..0000000000000
--- a/src/vs/workbench/contrib/notebook/browser/view/renderers/stdOutErrorPreProcessor.ts
+++ /dev/null
@@ -1,56 +0,0 @@
-/*---------------------------------------------------------------------------------------------
- *  Copyright (c) Microsoft Corporation. All rights reserved.
- *  Licensed under the MIT License. See License.txt in the project root for license information.
- *--------------------------------------------------------------------------------------------*/
-
-import { VSBuffer } from 'vs/base/common/buffer';
-import type { IOutputItemDto } from 'vs/workbench/contrib/notebook/common/notebookCommon';
-
-
-/**
- * Given a stream of individual stdout outputs, this function will return the compressed lines, escaping some of the common terminal escape codes.
- * E.g. some terminal escape codes would result in the previous line getting cleared, such if we had 3 lines and
- * last line contained such a code, then the result string would be just the first two lines.
- */
-export function compressOutputItemStreams(mimeType: string, outputs: IOutputItemDto[]) {
-	const buffers: Uint8Array[] = [];
-	let startAppending = false;
-
-	// Pick the first set of outputs with the same mime type.
-	for (const output of outputs) {
-		if (output.mime === mimeType) {
-			if ((buffers.length === 0 || startAppending)) {
-				buffers.push(output.data.buffer);
-				startAppending = true;
-			}
-		} else if (startAppending) {
-			startAppending = false;
-		}
-	}
-	compressStreamBuffer(buffers);
-	return VSBuffer.concat(buffers.map(buffer => VSBuffer.wrap(buffer))).buffer;
-}
-const MOVE_CURSOR_1_LINE_COMMAND = `${String.fromCharCode(27)}[A`;
-const MOVE_CURSOR_1_LINE_COMMAND_BYTES = MOVE_CURSOR_1_LINE_COMMAND.split('').map(c => c.charCodeAt(0));
-const LINE_FEED = 10;
-function compressStreamBuffer(streams: Uint8Array[]) {
-	streams.forEach((stream, index) => {
-		if (index === 0 || stream.length < MOVE_CURSOR_1_LINE_COMMAND.length) {
-			return;
-		}
-
-		const previousStream = streams[index - 1];
-
-		// Remove the previous line if required.
-		const command = stream.subarray(0, MOVE_CURSOR_1_LINE_COMMAND.length);
-		if (command[0] === MOVE_CURSOR_1_LINE_COMMAND_BYTES[0] && command[1] === MOVE_CURSOR_1_LINE_COMMAND_BYTES[1] && command[2] === MOVE_CURSOR_1_LINE_COMMAND_BYTES[2]) {
-			const lastIndexOfLineFeed = previousStream.lastIndexOf(LINE_FEED);
-			if (lastIndexOfLineFeed === -1) {
-				return;
-			}
-			streams[index - 1] = previousStream.subarray(0, lastIndexOfLineFeed);
-			streams[index] = stream.subarray(MOVE_CURSOR_1_LINE_COMMAND.length);
-		}
-	});
-	return streams;
-}
diff --git a/src/vs/workbench/contrib/notebook/common/notebookCommon.ts b/src/vs/workbench/contrib/notebook/common/notebookCommon.ts
index ab73eaf88b9f0..e77239c0a013e 100644
--- a/src/vs/workbench/contrib/notebook/common/notebookCommon.ts
+++ b/src/vs/workbench/contrib/notebook/common/notebookCommon.ts
@@ -949,11 +949,3 @@ export interface NotebookExtensionDescription {
 	readonly id: ExtensionIdentifier;
 	readonly location: UriComponents | undefined;
 }
-
-/**
- * Whether the provided mime type is a text streamn like `stdout`, `stderr`.
- */
-export function isTextStreamMime(mimeType: string) {
-	return ['application/vnd.code.notebook.stdout', 'application/x.notebook.stdout', 'application/x.notebook.stream', 'application/vnd.code.notebook.stderr', 'application/x.notebook.stderr'].includes(mimeType);
-}
-

From 47f133b55181e037d92aa6eff3154bbce1e1c5f3 Mon Sep 17 00:00:00 2001
From: Don Jayamanne <don.jayamanne@outlook.com>
Date: Fri, 16 Sep 2022 09:11:33 +1000
Subject: [PATCH 02/10] Compress stream output items

---
 extensions/ipynb/src/serializers.ts           |  2 +-
 .../api/common/extHostNotebookDocument.ts     |  8 ++
 .../view/renderers/backLayerWebView.ts        | 10 ++-
 .../common/model/notebookCellTextModel.ts     | 11 ++-
 .../contrib/notebook/common/notebookCommon.ts | 89 +++++++++++++++++++
 5 files changed, 114 insertions(+), 6 deletions(-)

diff --git a/extensions/ipynb/src/serializers.ts b/extensions/ipynb/src/serializers.ts
index 4f33b07a1501e..96da8f2c6178c 100644
--- a/extensions/ipynb/src/serializers.ts
+++ b/extensions/ipynb/src/serializers.ts
@@ -280,7 +280,7 @@ function convertStreamOutput(output: NotebookCellOutput): JupyterOutput {
 		.filter((opit) => opit.mime === CellOutputMimeTypes.stderr || opit.mime === CellOutputMimeTypes.stdout)
 		.map((opit) => textDecoder.decode(opit.data))
 		.forEach(value => {
-			// Ensure each line is a seprate entry in an array (ending with \n).
+			// Ensure each line is a separate entry in an array (ending with \n).
 			const lines = value.split('\n');
 			// If the last item in `outputs` is not empty and the first item in `lines` is not empty, then concate them.
 			// As they are part of the same line.
diff --git a/src/vs/workbench/api/common/extHostNotebookDocument.ts b/src/vs/workbench/api/common/extHostNotebookDocument.ts
index c3ebc53b3d6cb..7a687597b080f 100644
--- a/src/vs/workbench/api/common/extHostNotebookDocument.ts
+++ b/src/vs/workbench/api/common/extHostNotebookDocument.ts
@@ -110,6 +110,14 @@ export class ExtHostCell {
 				output.items.length = 0;
 			}
 			output.items.push(...newItems);
+			if (output.items.every(item => notebookCommon.isTextStreamMime(item.mime))) {
+				const compressed = notebookCommon.compressOutputItemStreams(newOutputItems[0].mime, output.items.map(item => item.data));
+				output.items.length = 0;
+				output.items.push({
+					mime: newOutputItems[0].mime,
+					data: compressed.buffer
+				});
+			}
 		}
 	}
 
diff --git a/src/vs/workbench/contrib/notebook/browser/view/renderers/backLayerWebView.ts b/src/vs/workbench/contrib/notebook/browser/view/renderers/backLayerWebView.ts
index a7eb492ad43c6..b64d96b817ccd 100644
--- a/src/vs/workbench/contrib/notebook/browser/view/renderers/backLayerWebView.ts
+++ b/src/vs/workbench/contrib/notebook/browser/view/renderers/backLayerWebView.ts
@@ -35,7 +35,7 @@ import { NOTEBOOK_WEBVIEW_BOUNDARY } from 'vs/workbench/contrib/notebook/browser
 import { preloadsScriptStr } from 'vs/workbench/contrib/notebook/browser/view/renderers/webviewPreloads';
 import { transformWebviewThemeVars } from 'vs/workbench/contrib/notebook/browser/view/renderers/webviewThemeMapping';
 import { MarkupCellViewModel } from 'vs/workbench/contrib/notebook/browser/viewModel/markupCellViewModel';
-import { CellUri, INotebookRendererInfo, NotebookSetting, RendererMessagingSpec } from 'vs/workbench/contrib/notebook/common/notebookCommon';
+import { CellUri, INotebookRendererInfo, isTextStreamMime, NotebookSetting, RendererMessagingSpec, compressOutputItemStreams } from 'vs/workbench/contrib/notebook/common/notebookCommon';
 import { INotebookKernel } from 'vs/workbench/contrib/notebook/common/notebookKernelService';
 import { IScopedRendererMessaging } from 'vs/workbench/contrib/notebook/common/notebookRendererMessagingService';
 import { INotebookService } from 'vs/workbench/contrib/notebook/common/notebookService';
@@ -1276,12 +1276,14 @@ var requirejs = (function() {
 		let updatedContent: ICreationContent | undefined = undefined;
 		if (content.type === RenderOutputType.Extension) {
 			const output = content.source.model;
-			const first = output.outputs.find(op => op.mime === content.mimeType)!;
+			const firstBuffer = isTextStreamMime(content.mimeType) ?
+				compressOutputItemStreams(content.mimeType, output.outputs.map(item => item.data.buffer)) :
+				output.outputs.find(op => op.mime === content.mimeType)!.data;
 			updatedContent = {
 				type: RenderOutputType.Extension,
 				outputId: outputCache.outputId,
-				mimeType: first.mime,
-				valueBytes: first.data.buffer,
+				mimeType: content.mimeType,
+				valueBytes: firstBuffer.buffer,
 				metadata: output.metadata,
 			};
 		}
diff --git a/src/vs/workbench/contrib/notebook/common/model/notebookCellTextModel.ts b/src/vs/workbench/contrib/notebook/common/model/notebookCellTextModel.ts
index 7890d2728929c..9e52dcc97fea4 100644
--- a/src/vs/workbench/contrib/notebook/common/model/notebookCellTextModel.ts
+++ b/src/vs/workbench/contrib/notebook/common/model/notebookCellTextModel.ts
@@ -16,7 +16,7 @@ import { TextModel } from 'vs/editor/common/model/textModel';
 import { PLAINTEXT_LANGUAGE_ID } from 'vs/editor/common/languages/modesRegistry';
 import { ILanguageService } from 'vs/editor/common/languages/language';
 import { NotebookCellOutputTextModel } from 'vs/workbench/contrib/notebook/common/model/notebookCellOutputTextModel';
-import { CellInternalMetadataChangedEvent, CellKind, ICell, ICellDto2, ICellOutput, IOutputDto, IOutputItemDto, NotebookCellCollapseState, NotebookCellInternalMetadata, NotebookCellMetadata, NotebookCellOutputsSplice, TransientOptions } from 'vs/workbench/contrib/notebook/common/notebookCommon';
+import { CellInternalMetadataChangedEvent, CellKind, compressOutputItemStreams, ICell, ICellDto2, ICellOutput, IOutputDto, IOutputItemDto, isTextStreamMime, NotebookCellCollapseState, NotebookCellInternalMetadata, NotebookCellMetadata, NotebookCellOutputsSplice, TransientOptions } from 'vs/workbench/contrib/notebook/common/notebookCommon';
 
 export class NotebookCellTextModel extends Disposable implements ICell {
 	private readonly _onDidChangeOutputs = this._register(new Emitter<NotebookCellOutputsSplice>());
@@ -297,6 +297,15 @@ export class NotebookCellTextModel extends Disposable implements ICell {
 		} else {
 			output.replaceData(items);
 		}
+		if (output.outputs.every(item => isTextStreamMime(item.mime))) {
+			const mime = output.outputs[0].mime;
+			const compressed = compressOutputItemStreams(output.outputs[0].mime, output.outputs.map(item => item.data.buffer));
+			output.outputs.length = 0;
+			output.outputs.push({
+				mime,
+				data: compressed
+			});
+		}
 
 		this._onDidChangeOutputItems.fire();
 		return true;
diff --git a/src/vs/workbench/contrib/notebook/common/notebookCommon.ts b/src/vs/workbench/contrib/notebook/common/notebookCommon.ts
index e77239c0a013e..6f56094ae2958 100644
--- a/src/vs/workbench/contrib/notebook/common/notebookCommon.ts
+++ b/src/vs/workbench/contrib/notebook/common/notebookCommon.ts
@@ -949,3 +949,92 @@ export interface NotebookExtensionDescription {
 	readonly id: ExtensionIdentifier;
 	readonly location: UriComponents | undefined;
 }
+
+/**
+ * Whether the provided mime type is a text streamn like `stdout`, `stderr`.
+ */
+export function isTextStreamMime(mimeType: string) {
+	return ['application/vnd.code.notebook.stdout', 'application/x.notebook.stdout', 'application/x.notebook.stream', 'application/vnd.code.notebook.stderr', 'application/x.notebook.stderr'].includes(mimeType);
+}
+
+
+
+/**
+ * Given a stream of individual stdout outputs, this function will return the compressed lines, escaping some of the common terminal escape codes.
+ * E.g. some terminal escape codes would result in the previous line getting cleared, such if we had 3 lines and
+ * last line contained such a code, then the result string would be just the first two lines.
+ */
+const textDecoder = new TextDecoder();
+export function compressOutputItemStreams(mimeType: string, outputs: Uint8Array[]) {
+	const buffers: Uint8Array[] = [];
+	let startAppending = false;
+
+	// Pick the first set of outputs with the same mime type.
+	for (const output of outputs) {
+		if ((buffers.length === 0 || startAppending)) {
+			buffers.push(output);
+			startAppending = true;
+		}
+	}
+	compressStreamBuffer(buffers);
+	const value = textDecoder.decode(VSBuffer.concat(buffers.map(buffer => VSBuffer.wrap(buffer))).buffer);
+	return VSBuffer.fromString(formatStreamText(value));
+}
+const MOVE_CURSOR_1_LINE_COMMAND = `${String.fromCharCode(27)}[A`;
+const MOVE_CURSOR_1_LINE_COMMAND_BYTES = MOVE_CURSOR_1_LINE_COMMAND.split('').map(c => c.charCodeAt(0));
+const LINE_FEED = 10;
+function compressStreamBuffer(streams: Uint8Array[]) {
+	streams.forEach((stream, index) => {
+		if (index === 0 || stream.length < MOVE_CURSOR_1_LINE_COMMAND.length) {
+			return;
+		}
+
+		const previousStream = streams[index - 1];
+
+		// Remove the previous line if required.
+		const command = stream.subarray(0, MOVE_CURSOR_1_LINE_COMMAND.length);
+		if (command[0] === MOVE_CURSOR_1_LINE_COMMAND_BYTES[0] && command[1] === MOVE_CURSOR_1_LINE_COMMAND_BYTES[1] && command[2] === MOVE_CURSOR_1_LINE_COMMAND_BYTES[2]) {
+			const lastIndexOfLineFeed = previousStream.lastIndexOf(LINE_FEED);
+			if (lastIndexOfLineFeed === -1) {
+				return;
+			}
+			streams[index - 1] = previousStream.subarray(0, lastIndexOfLineFeed);
+			streams[index] = stream.subarray(MOVE_CURSOR_1_LINE_COMMAND.length);
+		}
+	});
+	return streams;
+}
+
+
+
+// Took this from jupyter/notebook
+// https://github.com/jupyter/notebook/blob/b8b66332e2023e83d2ee04f83d8814f567e01a4e/notebook/static/base/js/utils.js
+// Remove characters that are overridden by backspace characters
+function fixBackspace(txt: string) {
+	let tmp = txt;
+	do {
+		txt = tmp;
+		// Cancel out anything-but-newline followed by backspace
+		tmp = txt.replace(/[^\n]\x08/gm, '');
+	} while (tmp.length < txt.length);
+	return txt;
+}
+
+// Remove chunks that should be overridden by the effect of
+// carriage return characters
+// From https://github.com/jupyter/notebook/blob/master/notebook/static/base/js/utils.js
+function fixCarriageReturn(txt: string) {
+	txt = txt.replace(/\r+\n/gm, '\n'); // \r followed by \n --> newline
+	while (txt.search(/\r[^$]/g) > -1) {
+		const base = txt.match(/^(.*)\r+/m)![1];
+		let insert = txt.match(/\r+(.*)$/m)![1];
+		insert = insert + base.slice(insert.length, base.length);
+		txt = txt.replace(/\r+.*$/m, '\r').replace(/^.*\r/m, insert);
+	}
+	return txt;
+}
+
+function formatStreamText(str: string): string {
+	// Do the same thing jupyter is doing
+	return fixCarriageReturn(fixBackspace(str));
+}

From 3ade74ad0acc8700bdd930fc44a22db2362f2b99 Mon Sep 17 00:00:00 2001
From: Don Jayamanne <don.jayamanne@outlook.com>
Date: Mon, 19 Sep 2022 15:05:35 +1000
Subject: [PATCH 03/10] Minor perf improvements

---
 .../api/common/extHostNotebookDocument.ts     | 28 +++++++++++++++----
 .../view/renderers/backLayerWebView.ts        |  6 ++--
 .../common/model/notebookCellTextModel.ts     | 28 +++++++++++++++----
 .../contrib/notebook/common/notebookCommon.ts | 16 +++++++----
 4 files changed, 57 insertions(+), 21 deletions(-)

diff --git a/src/vs/workbench/api/common/extHostNotebookDocument.ts b/src/vs/workbench/api/common/extHostNotebookDocument.ts
index 7a687597b080f..38437605cec08 100644
--- a/src/vs/workbench/api/common/extHostNotebookDocument.ts
+++ b/src/vs/workbench/api/common/extHostNotebookDocument.ts
@@ -110,12 +110,30 @@ export class ExtHostCell {
 				output.items.length = 0;
 			}
 			output.items.push(...newItems);
-			if (output.items.every(item => notebookCommon.isTextStreamMime(item.mime))) {
-				const compressed = notebookCommon.compressOutputItemStreams(newOutputItems[0].mime, output.items.map(item => item.data));
+
+			if (output.items.length > 1 && output.items.every(item => notebookCommon.isTextStreamMime(item.mime))) {
+				// Look for the mimes in the items, and keep track of their order.
+				// Merge the streams into one output item, per mime type.
+				const mimeOutputs = new Map<string, Uint8Array[]>();
+				const mimeTypes: string[] = [];
+				output.items.forEach(item => {
+					let items: Uint8Array[];
+					if (mimeOutputs.has(item.mime)) {
+						items = mimeOutputs.get(item.mime)!;
+					} else {
+						items = [];
+						mimeOutputs.set(item.mime, items);
+						mimeTypes.push(item.mime);
+					}
+					items.push(item.data);
+				});
 				output.items.length = 0;
-				output.items.push({
-					mime: newOutputItems[0].mime,
-					data: compressed.buffer
+				mimeTypes.forEach(mime => {
+					const compressed = notebookCommon.compressOutputItemStreams(mimeOutputs.get(mime)!);
+					output.items.push({
+						mime,
+						data: compressed.buffer
+					});
 				});
 			}
 		}
diff --git a/src/vs/workbench/contrib/notebook/browser/view/renderers/backLayerWebView.ts b/src/vs/workbench/contrib/notebook/browser/view/renderers/backLayerWebView.ts
index b64d96b817ccd..0facd39e9e110 100644
--- a/src/vs/workbench/contrib/notebook/browser/view/renderers/backLayerWebView.ts
+++ b/src/vs/workbench/contrib/notebook/browser/view/renderers/backLayerWebView.ts
@@ -35,7 +35,7 @@ import { NOTEBOOK_WEBVIEW_BOUNDARY } from 'vs/workbench/contrib/notebook/browser
 import { preloadsScriptStr } from 'vs/workbench/contrib/notebook/browser/view/renderers/webviewPreloads';
 import { transformWebviewThemeVars } from 'vs/workbench/contrib/notebook/browser/view/renderers/webviewThemeMapping';
 import { MarkupCellViewModel } from 'vs/workbench/contrib/notebook/browser/viewModel/markupCellViewModel';
-import { CellUri, INotebookRendererInfo, isTextStreamMime, NotebookSetting, RendererMessagingSpec, compressOutputItemStreams } from 'vs/workbench/contrib/notebook/common/notebookCommon';
+import { CellUri, INotebookRendererInfo, isTextStreamMime, NotebookSetting, RendererMessagingSpec } from 'vs/workbench/contrib/notebook/common/notebookCommon';
 import { INotebookKernel } from 'vs/workbench/contrib/notebook/common/notebookKernelService';
 import { IScopedRendererMessaging } from 'vs/workbench/contrib/notebook/common/notebookRendererMessagingService';
 import { INotebookService } from 'vs/workbench/contrib/notebook/common/notebookService';
@@ -1276,9 +1276,7 @@ var requirejs = (function() {
 		let updatedContent: ICreationContent | undefined = undefined;
 		if (content.type === RenderOutputType.Extension) {
 			const output = content.source.model;
-			const firstBuffer = isTextStreamMime(content.mimeType) ?
-				compressOutputItemStreams(content.mimeType, output.outputs.map(item => item.data.buffer)) :
-				output.outputs.find(op => op.mime === content.mimeType)!.data;
+			const firstBuffer = output.outputs.find(op => op.mime === content.mimeType)!.data;
 			updatedContent = {
 				type: RenderOutputType.Extension,
 				outputId: outputCache.outputId,
diff --git a/src/vs/workbench/contrib/notebook/common/model/notebookCellTextModel.ts b/src/vs/workbench/contrib/notebook/common/model/notebookCellTextModel.ts
index 9e52dcc97fea4..e8576c8234af9 100644
--- a/src/vs/workbench/contrib/notebook/common/model/notebookCellTextModel.ts
+++ b/src/vs/workbench/contrib/notebook/common/model/notebookCellTextModel.ts
@@ -297,13 +297,29 @@ export class NotebookCellTextModel extends Disposable implements ICell {
 		} else {
 			output.replaceData(items);
 		}
-		if (output.outputs.every(item => isTextStreamMime(item.mime))) {
-			const mime = output.outputs[0].mime;
-			const compressed = compressOutputItemStreams(output.outputs[0].mime, output.outputs.map(item => item.data.buffer));
+		if (output.outputs.length > 1 && output.outputs.every(item => isTextStreamMime(item.mime))) {
+			// Look for the mimes in the items, and keep track of their order.
+			// Merge the streams into one output item, per mime type.
+			const mimeOutputs = new Map<string, Uint8Array[]>();
+			const mimeTypes: string[] = [];
+			output.outputs.forEach(item => {
+				let items: Uint8Array[];
+				if (mimeOutputs.has(item.mime)) {
+					items = mimeOutputs.get(item.mime)!;
+				} else {
+					items = [];
+					mimeOutputs.set(item.mime, items);
+					mimeTypes.push(item.mime);
+				}
+				items.push(item.data.buffer);
+			});
 			output.outputs.length = 0;
-			output.outputs.push({
-				mime,
-				data: compressed
+			mimeTypes.forEach(mime => {
+				const compressed = compressOutputItemStreams(mimeOutputs.get(mime)!);
+				output.outputs.push({
+					mime,
+					data: compressed
+				});
 			});
 		}
 
diff --git a/src/vs/workbench/contrib/notebook/common/notebookCommon.ts b/src/vs/workbench/contrib/notebook/common/notebookCommon.ts
index 6f56094ae2958..27e5e0fe33c50 100644
--- a/src/vs/workbench/contrib/notebook/common/notebookCommon.ts
+++ b/src/vs/workbench/contrib/notebook/common/notebookCommon.ts
@@ -965,7 +965,7 @@ export function isTextStreamMime(mimeType: string) {
  * last line contained such a code, then the result string would be just the first two lines.
  */
 const textDecoder = new TextDecoder();
-export function compressOutputItemStreams(mimeType: string, outputs: Uint8Array[]) {
+export function compressOutputItemStreams(outputs: Uint8Array[]) {
 	const buffers: Uint8Array[] = [];
 	let startAppending = false;
 
@@ -977,8 +977,7 @@ export function compressOutputItemStreams(mimeType: string, outputs: Uint8Array[
 		}
 	}
 	compressStreamBuffer(buffers);
-	const value = textDecoder.decode(VSBuffer.concat(buffers.map(buffer => VSBuffer.wrap(buffer))).buffer);
-	return VSBuffer.fromString(formatStreamText(value));
+	return formatStreamText(VSBuffer.concat(buffers.map(buffer => VSBuffer.wrap(buffer))));
 }
 const MOVE_CURSOR_1_LINE_COMMAND = `${String.fromCharCode(27)}[A`;
 const MOVE_CURSOR_1_LINE_COMMAND_BYTES = MOVE_CURSOR_1_LINE_COMMAND.split('').map(c => c.charCodeAt(0));
@@ -1002,7 +1001,6 @@ function compressStreamBuffer(streams: Uint8Array[]) {
 			streams[index] = stream.subarray(MOVE_CURSOR_1_LINE_COMMAND.length);
 		}
 	});
-	return streams;
 }
 
 
@@ -1034,7 +1032,13 @@ function fixCarriageReturn(txt: string) {
 	return txt;
 }
 
-function formatStreamText(str: string): string {
+const BACKSPACE_CHARACTER = '\b'.charCodeAt(0);
+const CARRIAGE_RETURN_CHARACTER = '\r'.charCodeAt(0);
+function formatStreamText(buffer: VSBuffer): VSBuffer {
+	// We have special handling for backspace and carriage return characters.
+	if (!buffer.buffer.includes(BACKSPACE_CHARACTER) && !buffer.buffer.includes(CARRIAGE_RETURN_CHARACTER)) {
+		return buffer;
+	}
 	// Do the same thing jupyter is doing
-	return fixCarriageReturn(fixBackspace(str));
+	return VSBuffer.fromString(fixCarriageReturn(fixBackspace(textDecoder.decode(buffer.buffer))));
 }

From 2d6ce1ab2243affba4dc7f831ae673b5ebdcc967 Mon Sep 17 00:00:00 2001
From: Don Jayamanne <don.jayamanne@outlook.com>
Date: Mon, 19 Sep 2022 15:12:12 +1000
Subject: [PATCH 04/10] Misc

---
 .../contrib/notebook/browser/view/renderers/backLayerWebView.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/vs/workbench/contrib/notebook/browser/view/renderers/backLayerWebView.ts b/src/vs/workbench/contrib/notebook/browser/view/renderers/backLayerWebView.ts
index 0facd39e9e110..f01090a0561e8 100644
--- a/src/vs/workbench/contrib/notebook/browser/view/renderers/backLayerWebView.ts
+++ b/src/vs/workbench/contrib/notebook/browser/view/renderers/backLayerWebView.ts
@@ -35,7 +35,7 @@ import { NOTEBOOK_WEBVIEW_BOUNDARY } from 'vs/workbench/contrib/notebook/browser
 import { preloadsScriptStr } from 'vs/workbench/contrib/notebook/browser/view/renderers/webviewPreloads';
 import { transformWebviewThemeVars } from 'vs/workbench/contrib/notebook/browser/view/renderers/webviewThemeMapping';
 import { MarkupCellViewModel } from 'vs/workbench/contrib/notebook/browser/viewModel/markupCellViewModel';
-import { CellUri, INotebookRendererInfo, isTextStreamMime, NotebookSetting, RendererMessagingSpec } from 'vs/workbench/contrib/notebook/common/notebookCommon';
+import { CellUri, INotebookRendererInfo, NotebookSetting, RendererMessagingSpec } from 'vs/workbench/contrib/notebook/common/notebookCommon';
 import { INotebookKernel } from 'vs/workbench/contrib/notebook/common/notebookKernelService';
 import { IScopedRendererMessaging } from 'vs/workbench/contrib/notebook/common/notebookRendererMessagingService';
 import { INotebookService } from 'vs/workbench/contrib/notebook/common/notebookService';

From 554fc2cbca1c9b44078d46baee6d93f46e358bbc Mon Sep 17 00:00:00 2001
From: Don Jayamanne <don.jayamanne@outlook.com>
Date: Mon, 19 Sep 2022 15:22:56 +1000
Subject: [PATCH 05/10] Comments

---
 src/vs/workbench/contrib/notebook/common/notebookCommon.ts | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/vs/workbench/contrib/notebook/common/notebookCommon.ts b/src/vs/workbench/contrib/notebook/common/notebookCommon.ts
index 27e5e0fe33c50..ade4d44030c78 100644
--- a/src/vs/workbench/contrib/notebook/common/notebookCommon.ts
+++ b/src/vs/workbench/contrib/notebook/common/notebookCommon.ts
@@ -1036,6 +1036,7 @@ const BACKSPACE_CHARACTER = '\b'.charCodeAt(0);
 const CARRIAGE_RETURN_CHARACTER = '\r'.charCodeAt(0);
 function formatStreamText(buffer: VSBuffer): VSBuffer {
 	// We have special handling for backspace and carriage return characters.
+	// Don't unnecessary decode the bytes if we don't need to perform any processing.
 	if (!buffer.buffer.includes(BACKSPACE_CHARACTER) && !buffer.buffer.includes(CARRIAGE_RETURN_CHARACTER)) {
 		return buffer;
 	}

From 9ddbe3bb1930431be3f0fdbdd5ad738b62881a98 Mon Sep 17 00:00:00 2001
From: Don Jayamanne <don.jayamanne@outlook.com>
Date: Mon, 26 Sep 2022 12:30:41 +1000
Subject: [PATCH 06/10] Added tests

---
 src/vs/workbench/api/common/extHostTypes.ts   |   4 +-
 .../api/test/browser/extHostNotebook.test.ts  |  75 ++++++++++++-
 .../contrib/notebook/common/notebookCommon.ts |   2 +-
 .../test/browser/notebookTextModel.test.ts    | 106 ++++++++++++++++++
 4 files changed, 183 insertions(+), 4 deletions(-)

diff --git a/src/vs/workbench/api/common/extHostTypes.ts b/src/vs/workbench/api/common/extHostTypes.ts
index a717fa90515a1..f63260aa9fed2 100644
--- a/src/vs/workbench/api/common/extHostTypes.ts
+++ b/src/vs/workbench/api/common/extHostTypes.ts
@@ -17,7 +17,7 @@ import { IExtensionDescription } from 'vs/platform/extensions/common/extensions'
 import { FileSystemProviderErrorCode, markAsFileSystemProviderError } from 'vs/platform/files/common/files';
 import { RemoteAuthorityResolverErrorCode } from 'vs/platform/remote/common/remoteAuthorityResolver';
 import { IRelativePatternDto } from 'vs/workbench/api/common/extHost.protocol';
-import { CellEditType, ICellPartialMetadataEdit, IDocumentMetadataEdit } from 'vs/workbench/contrib/notebook/common/notebookCommon';
+import { CellEditType, ICellPartialMetadataEdit, IDocumentMetadataEdit, isTextStreamMime } from 'vs/workbench/contrib/notebook/common/notebookCommon';
 import { checkProposedApiEnabled } from 'vs/workbench/services/extensions/common/extensions';
 import type * as vscode from 'vscode';
 
@@ -3545,7 +3545,7 @@ export class NotebookCellOutput {
 		for (let i = 0; i < items.length; i++) {
 			const item = items[i];
 			const normalMime = normalizeMimeType(item.mime);
-			if (!seen.has(normalMime)) {
+			if (!seen.has(normalMime) && !isTextStreamMime(item.mime)) {
 				seen.add(normalMime);
 				continue;
 			}
diff --git a/src/vs/workbench/api/test/browser/extHostNotebook.test.ts b/src/vs/workbench/api/test/browser/extHostNotebook.test.ts
index 09e785c307b25..60f453ec1f3c1 100644
--- a/src/vs/workbench/api/test/browser/extHostNotebook.test.ts
+++ b/src/vs/workbench/api/test/browser/extHostNotebook.test.ts
@@ -10,7 +10,7 @@ import { TestRPCProtocol } from 'vs/workbench/api/test/common/testRPCProtocol';
 import { DisposableStore } from 'vs/base/common/lifecycle';
 import { NullLogService } from 'vs/platform/log/common/log';
 import { mock } from 'vs/base/test/common/mock';
-import { IModelAddedData, MainContext, MainThreadCommandsShape, MainThreadNotebookShape } from 'vs/workbench/api/common/extHost.protocol';
+import { IModelAddedData, MainContext, MainThreadCommandsShape, MainThreadNotebookShape, NotebookCellsChangedEventDto, NotebookOutputItemDto } from 'vs/workbench/api/common/extHost.protocol';
 import { ExtHostNotebookController } from 'vs/workbench/api/common/extHostNotebook';
 import { ExtHostNotebookDocument } from 'vs/workbench/api/common/extHostNotebookDocument';
 import { CellKind, CellUri, NotebookCellsChangeType } from 'vs/workbench/contrib/notebook/common/notebookCommon';
@@ -542,4 +542,77 @@ suite('NotebookCell#Document', function () {
 		assert.ok(cellChange.metadata === undefined);
 		assert.ok(cellChange.outputs === undefined);
 	});
+
+	async function replaceOutputs(cellIndex: number, outputId: string, outputItems: NotebookOutputItemDto[]) {
+		const changeEvent = Event.toPromise(extHostNotebookDocuments.onDidChangeNotebookDocument);
+		extHostNotebookDocuments.$acceptModelChanged(notebook.uri, new SerializableObjectWithBuffers<NotebookCellsChangedEventDto>({
+			versionId: notebook.apiNotebook.version + 1,
+			rawEvents: [{
+				kind: NotebookCellsChangeType.Output,
+				index: cellIndex,
+				outputs: [{ outputId, items: outputItems }]
+			}]
+		}), false);
+		await changeEvent;
+	}
+	async function appendOutputItem(cellIndex: number, outputId: string, outputItems: NotebookOutputItemDto[]) {
+		const changeEvent = Event.toPromise(extHostNotebookDocuments.onDidChangeNotebookDocument);
+		extHostNotebookDocuments.$acceptModelChanged(notebook.uri, new SerializableObjectWithBuffers<NotebookCellsChangedEventDto>({
+			versionId: notebook.apiNotebook.version + 1,
+			rawEvents: [{
+				kind: NotebookCellsChangeType.OutputItem,
+				index: cellIndex,
+				append: true,
+				outputId,
+				outputItems
+			}]
+		}), false);
+		await changeEvent;
+	}
+	test('Append multiple text/plain output items', async function () {
+		await replaceOutputs(1, '1', [{ mime: 'text/plain', valueBytes: VSBuffer.fromString('foo') }]);
+		await appendOutputItem(1, '1', [{ mime: 'text/plain', valueBytes: VSBuffer.fromString('bar') }]);
+		await appendOutputItem(1, '1', [{ mime: 'text/plain', valueBytes: VSBuffer.fromString('baz') }]);
+
+
+		assert.strictEqual(notebook.apiNotebook.cellAt(1).outputs.length, 1);
+		assert.strictEqual(notebook.apiNotebook.cellAt(1).outputs[0].items.length, 3);
+		assert.strictEqual(notebook.apiNotebook.cellAt(1).outputs[0].items[0].mime, 'text/plain');
+		assert.strictEqual(VSBuffer.wrap(notebook.apiNotebook.cellAt(1).outputs[0].items[0].data).toString(), 'foo');
+		assert.strictEqual(notebook.apiNotebook.cellAt(1).outputs[0].items[1].mime, 'text/plain');
+		assert.strictEqual(VSBuffer.wrap(notebook.apiNotebook.cellAt(1).outputs[0].items[1].data).toString(), 'bar');
+		assert.strictEqual(notebook.apiNotebook.cellAt(1).outputs[0].items[2].mime, 'text/plain');
+		assert.strictEqual(VSBuffer.wrap(notebook.apiNotebook.cellAt(1).outputs[0].items[2].data).toString(), 'baz');
+	});
+	test('Append multiple stdout stream output items to an output with another mime', async function () {
+		await replaceOutputs(1, '1', [{ mime: 'text/plain', valueBytes: VSBuffer.fromString('foo') }]);
+		await appendOutputItem(1, '1', [{ mime: 'application/vnd.code.notebook.stdout', valueBytes: VSBuffer.fromString('bar') }]);
+		await appendOutputItem(1, '1', [{ mime: 'application/vnd.code.notebook.stdout', valueBytes: VSBuffer.fromString('baz') }]);
+
+		assert.strictEqual(notebook.apiNotebook.cellAt(1).outputs.length, 1);
+		assert.strictEqual(notebook.apiNotebook.cellAt(1).outputs[0].items.length, 3);
+		assert.strictEqual(notebook.apiNotebook.cellAt(1).outputs[0].items[0].mime, 'text/plain');
+		assert.strictEqual(notebook.apiNotebook.cellAt(1).outputs[0].items[1].mime, 'application/vnd.code.notebook.stdout');
+		assert.strictEqual(notebook.apiNotebook.cellAt(1).outputs[0].items[2].mime, 'application/vnd.code.notebook.stdout');
+	});
+	test('Compress multiple stdout stream output items', async function () {
+		await replaceOutputs(1, '1', [{ mime: 'application/vnd.code.notebook.stdout', valueBytes: VSBuffer.fromString('foo') }]);
+		await appendOutputItem(1, '1', [{ mime: 'application/vnd.code.notebook.stdout', valueBytes: VSBuffer.fromString('bar') }]);
+		await appendOutputItem(1, '1', [{ mime: 'application/vnd.code.notebook.stdout', valueBytes: VSBuffer.fromString('baz') }]);
+
+		assert.strictEqual(notebook.apiNotebook.cellAt(1).outputs.length, 1);
+		assert.strictEqual(notebook.apiNotebook.cellAt(1).outputs[0].items.length, 1);
+		assert.strictEqual(notebook.apiNotebook.cellAt(1).outputs[0].items[0].mime, 'application/vnd.code.notebook.stdout');
+		assert.strictEqual(VSBuffer.wrap(notebook.apiNotebook.cellAt(1).outputs[0].items[0].data).toString(), 'foobarbaz');
+	});
+	test('Compress multiple stderr stream output items', async function () {
+		await replaceOutputs(1, '1', [{ mime: 'application/vnd.code.notebook.stderr', valueBytes: VSBuffer.fromString('foo') }]);
+		await appendOutputItem(1, '1', [{ mime: 'application/vnd.code.notebook.stderr', valueBytes: VSBuffer.fromString('bar') }]);
+		await appendOutputItem(1, '1', [{ mime: 'application/vnd.code.notebook.stderr', valueBytes: VSBuffer.fromString('baz') }]);
+
+		assert.strictEqual(notebook.apiNotebook.cellAt(1).outputs.length, 1);
+		assert.strictEqual(notebook.apiNotebook.cellAt(1).outputs[0].items.length, 1);
+		assert.strictEqual(notebook.apiNotebook.cellAt(1).outputs[0].items[0].mime, 'application/vnd.code.notebook.stderr');
+		assert.strictEqual(VSBuffer.wrap(notebook.apiNotebook.cellAt(1).outputs[0].items[0].data).toString(), 'foobarbaz');
+	});
 });
diff --git a/src/vs/workbench/contrib/notebook/common/notebookCommon.ts b/src/vs/workbench/contrib/notebook/common/notebookCommon.ts
index ade4d44030c78..d7fb943b513dc 100644
--- a/src/vs/workbench/contrib/notebook/common/notebookCommon.ts
+++ b/src/vs/workbench/contrib/notebook/common/notebookCommon.ts
@@ -954,7 +954,7 @@ export interface NotebookExtensionDescription {
  * Whether the provided mime type is a text streamn like `stdout`, `stderr`.
  */
 export function isTextStreamMime(mimeType: string) {
-	return ['application/vnd.code.notebook.stdout', 'application/x.notebook.stdout', 'application/x.notebook.stream', 'application/vnd.code.notebook.stderr', 'application/x.notebook.stderr'].includes(mimeType);
+	return ['application/vnd.code.notebook.stdout', 'application/vnd.code.notebook.stderr'].includes(mimeType);
 }
 
 
diff --git a/src/vs/workbench/contrib/notebook/test/browser/notebookTextModel.test.ts b/src/vs/workbench/contrib/notebook/test/browser/notebookTextModel.test.ts
index 455d706b63745..4da03a9f24814 100644
--- a/src/vs/workbench/contrib/notebook/test/browser/notebookTextModel.test.ts
+++ b/src/vs/workbench/contrib/notebook/test/browser/notebookTextModel.test.ts
@@ -1043,4 +1043,110 @@ suite('NotebookTextModel', () => {
 			assert.equal(model.cells[0].outputs[0].outputs[0].data.toString(), '_World_');
 		});
 	});
+	test('Append multiple text/plain output items', async function () {
+		await withTestNotebook([
+			['var a = 1;', 'javascript', CellKind.Code, [{
+				outputId: '1',
+				outputs: [{ mime: 'text/plain', data: valueBytesFromString('foo') }]
+			}], {}]
+		], (editor) => {
+			const model = editor.textModel;
+			const edits: ICellEditOperation[] = [
+				{
+					editType: CellEditType.OutputItems,
+					outputId: '1',
+					append: true,
+					items: [{ mime: 'text/plain', data: VSBuffer.fromString('bar') }, { mime: 'text/plain', data: VSBuffer.fromString('baz') }]
+				}
+			];
+			model.applyEdits(edits, true, undefined, () => undefined, undefined, true);
+			assert.equal(model.cells.length, 1);
+			assert.equal(model.cells[0].outputs.length, 1);
+			assert.equal(model.cells[0].outputs[0].outputs.length, 3);
+			assert.equal(model.cells[0].outputs[0].outputs[0].mime, 'text/plain');
+			assert.equal(model.cells[0].outputs[0].outputs[0].data.toString(), 'foo');
+			assert.equal(model.cells[0].outputs[0].outputs[1].mime, 'text/plain');
+			assert.equal(model.cells[0].outputs[0].outputs[1].data.toString(), 'bar');
+			assert.equal(model.cells[0].outputs[0].outputs[2].mime, 'text/plain');
+			assert.equal(model.cells[0].outputs[0].outputs[2].data.toString(), 'baz');
+		});
+	});
+	test('Append multiple stdout stream output items to an output with another mime', async function () {
+		await withTestNotebook([
+			['var a = 1;', 'javascript', CellKind.Code, [{
+				outputId: '1',
+				outputs: [{ mime: 'text/plain', data: valueBytesFromString('foo') }]
+			}], {}]
+		], (editor) => {
+			const model = editor.textModel;
+			const edits: ICellEditOperation[] = [
+				{
+					editType: CellEditType.OutputItems,
+					outputId: '1',
+					append: true,
+					items: [{ mime: 'application/vnd.code.notebook.stdout', data: VSBuffer.fromString('bar') }, { mime: 'application/vnd.code.notebook.stdout', data: VSBuffer.fromString('baz') }]
+				}
+			];
+			model.applyEdits(edits, true, undefined, () => undefined, undefined, true);
+			assert.equal(model.cells.length, 1);
+			assert.equal(model.cells[0].outputs.length, 1);
+			assert.equal(model.cells[0].outputs[0].outputs.length, 3);
+			assert.equal(model.cells[0].outputs[0].outputs[0].mime, 'text/plain');
+			assert.equal(model.cells[0].outputs[0].outputs[0].data.toString(), 'foo');
+			assert.equal(model.cells[0].outputs[0].outputs[1].mime, 'application/vnd.code.notebook.stdout');
+			assert.equal(model.cells[0].outputs[0].outputs[1].data.toString(), 'bar');
+			assert.equal(model.cells[0].outputs[0].outputs[2].mime, 'application/vnd.code.notebook.stdout');
+			assert.equal(model.cells[0].outputs[0].outputs[2].data.toString(), 'baz');
+		});
+	});
+	test('Compress multiple stdout stream output items', async function () {
+		await withTestNotebook([
+			['var a = 1;', 'javascript', CellKind.Code, [{
+				outputId: '1',
+				outputs: [{ mime: 'application/vnd.code.notebook.stdout', data: valueBytesFromString('foo') }]
+			}], {}]
+		], (editor) => {
+			const model = editor.textModel;
+			const edits: ICellEditOperation[] = [
+				{
+					editType: CellEditType.OutputItems,
+					outputId: '1',
+					append: true,
+					items: [{ mime: 'application/vnd.code.notebook.stdout', data: VSBuffer.fromString('bar') }, { mime: 'application/vnd.code.notebook.stdout', data: VSBuffer.fromString('baz') }]
+				}
+			];
+			model.applyEdits(edits, true, undefined, () => undefined, undefined, true);
+			assert.equal(model.cells.length, 1);
+			assert.equal(model.cells[0].outputs.length, 1);
+			assert.equal(model.cells[0].outputs[0].outputs.length, 1);
+			assert.equal(model.cells[0].outputs[0].outputs[0].mime, 'application/vnd.code.notebook.stdout');
+			assert.equal(model.cells[0].outputs[0].outputs[0].data.toString(), 'foobarbaz');
+		});
+
+	});
+	test('Compress multiple stderr stream output items', async function () {
+		await withTestNotebook([
+			['var a = 1;', 'javascript', CellKind.Code, [{
+				outputId: '1',
+				outputs: [{ mime: 'application/vnd.code.notebook.stderr', data: valueBytesFromString('foo') }]
+			}], {}]
+		], (editor) => {
+			const model = editor.textModel;
+			const edits: ICellEditOperation[] = [
+				{
+					editType: CellEditType.OutputItems,
+					outputId: '1',
+					append: true,
+					items: [{ mime: 'application/vnd.code.notebook.stderr', data: VSBuffer.fromString('bar') }, { mime: 'application/vnd.code.notebook.stderr', data: VSBuffer.fromString('baz') }]
+				}
+			];
+			model.applyEdits(edits, true, undefined, () => undefined, undefined, true);
+			assert.equal(model.cells.length, 1);
+			assert.equal(model.cells[0].outputs.length, 1);
+			assert.equal(model.cells[0].outputs[0].outputs.length, 1);
+			assert.equal(model.cells[0].outputs[0].outputs[0].mime, 'application/vnd.code.notebook.stderr');
+			assert.equal(model.cells[0].outputs[0].outputs[0].data.toString(), 'foobarbaz');
+		});
+
+	});
 });

From 0a8e55dace4dcad79ed466899162ec822a315e83 Mon Sep 17 00:00:00 2001
From: Don Jayamanne <don.jayamanne@outlook.com>
Date: Mon, 26 Sep 2022 12:32:44 +1000
Subject: [PATCH 07/10] Merge issue

---
 src/vs/workbench/api/common/extHostTypes.ts | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/vs/workbench/api/common/extHostTypes.ts b/src/vs/workbench/api/common/extHostTypes.ts
index f63260aa9fed2..ed7553b4adbcb 100644
--- a/src/vs/workbench/api/common/extHostTypes.ts
+++ b/src/vs/workbench/api/common/extHostTypes.ts
@@ -3545,7 +3545,8 @@ export class NotebookCellOutput {
 		for (let i = 0; i < items.length; i++) {
 			const item = items[i];
 			const normalMime = normalizeMimeType(item.mime);
-			if (!seen.has(normalMime) && !isTextStreamMime(item.mime)) {
+			// We can have multiple text stream mime types in the same output.
+			if (!seen.has(normalMime) || isTextStreamMime(item.mime)) {
 				seen.add(normalMime);
 				continue;
 			}

From 3219f4927ca2987b2e7d73378ec3ea5cd430c3d8 Mon Sep 17 00:00:00 2001
From: Don Jayamanne <don.jayamanne@outlook.com>
Date: Mon, 26 Sep 2022 12:33:38 +1000
Subject: [PATCH 08/10] More merge issues

---
 src/vs/workbench/api/common/extHostTypes.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/vs/workbench/api/common/extHostTypes.ts b/src/vs/workbench/api/common/extHostTypes.ts
index ed7553b4adbcb..f7b89d987a907 100644
--- a/src/vs/workbench/api/common/extHostTypes.ts
+++ b/src/vs/workbench/api/common/extHostTypes.ts
@@ -3546,7 +3546,7 @@ export class NotebookCellOutput {
 			const item = items[i];
 			const normalMime = normalizeMimeType(item.mime);
 			// We can have multiple text stream mime types in the same output.
-			if (!seen.has(normalMime) || isTextStreamMime(item.mime)) {
+			if (!seen.has(normalMime) || isTextStreamMime(normalMime)) {
 				seen.add(normalMime);
 				continue;
 			}

From 06f5422bec9943d3bc266caf362e9d991fea4fab Mon Sep 17 00:00:00 2001
From: Don Jayamanne <don.jayamanne@outlook.com>
Date: Mon, 26 Sep 2022 13:08:02 +1000
Subject: [PATCH 09/10] Misc

---
 src/vs/workbench/contrib/notebook/common/notebookCommon.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/vs/workbench/contrib/notebook/common/notebookCommon.ts b/src/vs/workbench/contrib/notebook/common/notebookCommon.ts
index d7fb943b513dc..02b9e0ddcc2d4 100644
--- a/src/vs/workbench/contrib/notebook/common/notebookCommon.ts
+++ b/src/vs/workbench/contrib/notebook/common/notebookCommon.ts
@@ -951,7 +951,7 @@ export interface NotebookExtensionDescription {
 }
 
 /**
- * Whether the provided mime type is a text streamn like `stdout`, `stderr`.
+ * Whether the provided mime type is a text stream like `stdout`, `stderr`.
  */
 export function isTextStreamMime(mimeType: string) {
 	return ['application/vnd.code.notebook.stdout', 'application/vnd.code.notebook.stderr'].includes(mimeType);

From 42522fdedbd9343ab26610bc52e98422a2028f9b Mon Sep 17 00:00:00 2001
From: Don Jayamanne <don.jayamanne@outlook.com>
Date: Wed, 12 Oct 2022 07:14:59 +1100
Subject: [PATCH 10/10] Address code review comments

---
 .../contrib/notebook/common/notebookCommon.ts   | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/src/vs/workbench/contrib/notebook/common/notebookCommon.ts b/src/vs/workbench/contrib/notebook/common/notebookCommon.ts
index 02b9e0ddcc2d4..0e2f1fe9ea62a 100644
--- a/src/vs/workbench/contrib/notebook/common/notebookCommon.ts
+++ b/src/vs/workbench/contrib/notebook/common/notebookCommon.ts
@@ -958,13 +958,13 @@ export function isTextStreamMime(mimeType: string) {
 }
 
 
+const textDecoder = new TextDecoder();
 
 /**
  * Given a stream of individual stdout outputs, this function will return the compressed lines, escaping some of the common terminal escape codes.
  * E.g. some terminal escape codes would result in the previous line getting cleared, such if we had 3 lines and
  * last line contained such a code, then the result string would be just the first two lines.
  */
-const textDecoder = new TextDecoder();
 export function compressOutputItemStreams(outputs: Uint8Array[]) {
 	const buffers: Uint8Array[] = [];
 	let startAppending = false;
@@ -1005,9 +1005,11 @@ function compressStreamBuffer(streams: Uint8Array[]) {
 
 
 
-// Took this from jupyter/notebook
-// https://github.com/jupyter/notebook/blob/b8b66332e2023e83d2ee04f83d8814f567e01a4e/notebook/static/base/js/utils.js
-// Remove characters that are overridden by backspace characters
+/**
+ * Took this from jupyter/notebook
+ * https://github.com/jupyter/notebook/blob/b8b66332e2023e83d2ee04f83d8814f567e01a4e/notebook/static/base/js/utils.js
+ * Remove characters that are overridden by backspace characters
+ */
 function fixBackspace(txt: string) {
 	let tmp = txt;
 	do {
@@ -1018,9 +1020,10 @@ function fixBackspace(txt: string) {
 	return txt;
 }
 
-// Remove chunks that should be overridden by the effect of
-// carriage return characters
-// From https://github.com/jupyter/notebook/blob/master/notebook/static/base/js/utils.js
+/**
+ * Remove chunks that should be overridden by the effect of carriage return characters
+ * From https://github.com/jupyter/notebook/blob/master/notebook/static/base/js/utils.js
+ */
 function fixCarriageReturn(txt: string) {
 	txt = txt.replace(/\r+\n/gm, '\n'); // \r followed by \n --> newline
 	while (txt.search(/\r[^$]/g) > -1) {