fix(rosetta): prints colors to log file (#3953)

Rosetta error messages contain colors codes in the errors, which makes the errors produced by Rosetta look like garbage and very hard to parse.

Strip the colors if we detect a non-TTY input.

(Copied the regex from an MIT-licensed package to avoid adding extra dependencies)



---

By submitting this pull request, I confirm that my contribution is made under the terms of the [Apache 2.0 license].

[Apache 2.0 license]: https://www.apache.org/licenses/LICENSE-2.0

packages/jsii-rosetta/bin/jsii-rosetta.ts

@@ -514,7 +514,7 @@ function handleDiagnostics(diagnostics: readonly RosettaDiagnostic[], fail: bool
   if (fail !== false) {
     // Fail on any diagnostic
     if (diagnostics.length > 0) {
-      printDiagnostics(diagnostics, process.stderr);
+      printDiagnostics(diagnostics, process.stderr, process.stderr.isTTY);
       logging.error(
         [
           `${diagnostics.length} diagnostics encountered in ${snippetCount} snippets`,
@@ -531,7 +531,7 @@ function handleDiagnostics(diagnostics: readonly RosettaDiagnostic[], fail: bool
   // (so it's very clear what is failing the build), otherwise print everything.
   const strictDiagnostics = diagnostics.filter((diag) => diag.isFromStrictAssembly);
   if (strictDiagnostics.length > 0) {
-    printDiagnostics(strictDiagnostics, process.stderr);
+    printDiagnostics(strictDiagnostics, process.stderr, process.stderr.isTTY);
     const remaining = diagnostics.length - strictDiagnostics.length;
     logging.warn(
       [
@@ -544,7 +544,7 @@ function handleDiagnostics(diagnostics: readonly RosettaDiagnostic[], fail: bool
   }
 
   if (diagnostics.length > 0) {
-    printDiagnostics(diagnostics, process.stderr);
+    printDiagnostics(diagnostics, process.stderr, process.stderr.isTTY);
     logging.warn(`${diagnostics.length} diagnostics encountered in ${snippetCount} snippets`);
   }
 }

packages/jsii-rosetta/lib/commands/transliterate.ts

@@ -126,7 +126,7 @@ export async function transliterateAssembly(
     }
   }
 
-  rosetta.printDiagnostics(process.stderr);
+  rosetta.printDiagnostics(process.stderr, process.stderr.isTTY);
   if (rosetta.hasErrors && options.strict) {
     throw new Error('Strict mode is enabled and some examples failed compilation!');
   }

packages/jsii-rosetta/lib/rosetta-reader.ts

@@ -293,8 +293,8 @@ export class RosettaTabletReader {
     );
   }
 
-  public printDiagnostics(stream: NodeJS.WritableStream) {
-    printDiagnostics(this.diagnostics, stream);
+  public printDiagnostics(stream: NodeJS.WritableStream, colors = true) {
+    printDiagnostics(this.diagnostics, stream, colors);
   }
 
   public get hasErrors() {

packages/jsii-rosetta/lib/util.ts

@@ -12,12 +12,12 @@ export interface File {
   readonly fileName: string;
 }
 
-export function printDiagnostics(diags: readonly RosettaDiagnostic[], stream: NodeJS.WritableStream) {
+export function printDiagnostics(diags: readonly RosettaDiagnostic[], stream: NodeJS.WritableStream, colors: boolean) {
   // Don't print too much, at some point it just clogs up the log
   const maxDiags = 50;
 
   for (const diag of diags.slice(0, maxDiags)) {
-    stream.write(diag.formattedMessage);
+    stream.write(colors ? diag.formattedMessage : stripColorCodes(diag.formattedMessage));
   }
 
   if (diags.length > maxDiags) {
@@ -243,3 +243,16 @@ export async function pathExists(path: string): Promise<boolean> {
     throw err;
   }
 }
+
+// Copy/pasted from the 'ansi-regex' package to avoid taking a dependency for this one line that will never change
+const ANSI_PATTERN = new RegExp(
+  [
+    '[\\u001B\\u009B][[\\]()#;?]*(?:(?:(?:(?:;[-a-zA-Z\\d\\/#&.:=?%@~_]+)*|[a-zA-Z\\d]+(?:;[-a-zA-Z\\d\\/#&.:=?%@~_]*)*)?\\u0007)',
+    '(?:(?:\\d{1,4}(?:;\\d{0,4})*)?[\\dA-PR-TZcf-nq-uy=><~]))',
+  ].join('|'),
+  'g',
+);
+
+function stripColorCodes(x: string) {
+  return x.replace(ANSI_PATTERN, '');
+}