Allow to combine --resolveJsonModule with --isolatedModules (#28207)

src/compiler/program.ts

@@ -2667,13 +2667,13 @@ namespace ts {
             const languageVersion = options.target || ScriptTarget.ES3;
             const outFile = options.outFile || options.out;
 
-            const firstNonAmbientExternalModuleSourceFile = forEach(files, f => isExternalModule(f) && !f.isDeclarationFile ? f : undefined);
+            const firstNonAmbientExternalModuleSourceFile = find(files, f => isExternalModule(f) && !f.isDeclarationFile);
             if (options.isolatedModules) {
                 if (options.module === ModuleKind.None && languageVersion < ScriptTarget.ES2015) {
                     createDiagnosticForOptionName(Diagnostics.Option_isolatedModules_can_only_be_used_when_either_option_module_is_provided_or_option_target_is_ES2015_or_higher, "isolatedModules", "target");
                 }
 
-                const firstNonExternalModuleSourceFile = forEach(files, f => !isExternalModule(f) && !f.isDeclarationFile ? f : undefined);
+                const firstNonExternalModuleSourceFile = find(files, f => !isExternalModule(f) && !f.isDeclarationFile && f.scriptKind !== ScriptKind.JSON);
                 if (firstNonExternalModuleSourceFile) {
                     const span = getErrorSpanForNode(firstNonExternalModuleSourceFile, firstNonExternalModuleSourceFile);
                     programDiagnostics.add(createFileDiagnostic(firstNonExternalModuleSourceFile, span.start, span.length, Diagnostics.Cannot_compile_namespaces_when_the_isolatedModules_flag_is_provided));
@@ -2716,7 +2716,7 @@ namespace ts {
                 const dir = getCommonSourceDirectory();
 
                 // If we failed to find a good common directory, but outDir is specified and at least one of our files is on a windows drive/URL/other resource, add a failure
-                if (options.outDir && dir === "" && forEach(files, file => getRootLength(file.fileName) > 1)) {
+                if (options.outDir && dir === "" && files.some(file => getRootLength(file.fileName) > 1)) {
                     createDiagnosticForOptionName(Diagnostics.Cannot_find_the_common_subdirectory_path_for_the_input_files, "outDir");
                 }
             }

tests/baselines/reference/isolatedModules_resolveJsonModule.js

@@ -0,0 +1,12 @@
+//// [tests/cases/compiler/isolatedModules_resolveJsonModule.ts] ////
+
+//// [a.ts]
+import j = require("./j.json");
+
+//// [j.json]
+{}
+
+
+//// [a.js]
+"use strict";
+exports.__esModule = true;

tests/baselines/reference/isolatedModules_resolveJsonModule.symbols

@@ -0,0 +1,8 @@
+=== /a.ts ===
+import j = require("./j.json");
+>j : Symbol(j, Decl(a.ts, 0, 0))
+
+=== /j.json ===
+{}
+No type information for this code.
+No type information for this code.

tests/baselines/reference/isolatedModules_resolveJsonModule.types

@@ -0,0 +1,8 @@
+=== /a.ts ===
+import j = require("./j.json");
+>j : {}
+
+=== /j.json ===
+{}
+>{} : {}
+

tests/cases/compiler/isolatedModules_resolveJsonModule.ts

@@ -0,0 +1,8 @@
+// @isolatedModules: true
+// @resolveJsonModule: true
+
+// @Filename: /a.ts
+import j = require("./j.json");
+
+// @Filename: /j.json
+{}