Assume rootDir is the current configuration directory

src/compiler/diagnosticMessages.json

@@ -1539,7 +1539,6 @@
         "category": "Error",
         "code": 1464
     },
-
     "The 'import.meta' meta-property is not allowed in files which will build into CommonJS output.": {
         "category": "Error",
         "code": 1470
@@ -1849,7 +1848,6 @@
         "category": "Error",
         "code": 1546
     },
-
     "The types of '{0}' are incompatible between these types.": {
         "category": "Error",
         "code": 2200
@@ -1890,7 +1888,6 @@
         "category": "Error",
         "code": 2208
     },
-
     "The project root is ambiguous, but is required to resolve export map entry '{0}' in file '{1}'. Supply the `rootDir` compiler option to disambiguate.": {
         "category": "Error",
         "code": 2209
@@ -1907,7 +1904,6 @@
         "category": "Message",
         "code": 2212
     },
-
     "Duplicate identifier '{0}'.": {
         "category": "Error",
         "code": 2300
@@ -2888,7 +2884,6 @@
         "category": "Error",
         "code": 2568
     },
-
     "Could not find name '{0}'. Did you mean '{1}'?": {
         "category": "Error",
         "code": 2570
@@ -3129,7 +3124,6 @@
         "category": "Error",
         "code": 2639
     },
-
     "Cannot augment module '{0}' with value exports because it resolves to a non-module entity.": {
         "category": "Error",
         "code": 2649
@@ -4007,7 +4001,6 @@
         "category": "Error",
         "code": 2881
     },
-
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",
         "code": 4000
@@ -4452,7 +4445,6 @@
         "category": "Error",
         "code": 4128
     },
-
     "The current host does not support the '{0}' option.": {
         "category": "Error",
         "code": 5001
@@ -4465,6 +4457,10 @@
         "category": "Error",
         "code": 5010
     },
+    "Inferred common source directory differs from tsconfig directory, output layout will be changed.": {
+        "category": "Error",
+        "code": 5011
+    },
     "Cannot read file '{0}': {1}.": {
         "category": "Error",
         "code": 5012
@@ -4717,7 +4713,10 @@
         "category": "Error",
         "code": 5110
     },
-
+    "Visit https://aka.ms/ts6 for migration information.": {
+        "category": "Message",
+        "code": 5111
+    },
     "Generates a sourcemap for each corresponding '.d.ts' file.": {
         "category": "Message",
         "code": 6000
@@ -5661,7 +5660,6 @@
         "category": "Error",
         "code": 6266
     },
-
     "Directory '{0}' has no containing package.json scope. Imports will not resolve.": {
         "category": "Message",
         "code": 6270
@@ -5754,7 +5752,6 @@
         "category": "Message",
         "code": 6294
     },
-
     "Enable project compilation": {
         "category": "Message",
         "code": 6302
@@ -6037,7 +6034,6 @@
         "category": "Message",
         "code": 6421
     },
-
     "The expected type comes from property '{0}' which is declared here on type '{1}'": {
         "category": "Message",
         "code": 6500
@@ -6562,7 +6558,6 @@
         "category": "Message",
         "code": 6808
     },
-
     "one of:": {
         "category": "Message",
         "code": 6900
@@ -6691,7 +6686,6 @@
         "category": "Error",
         "code": 6931
     },
-
     "Variable '{0}' implicitly has an '{1}' type.": {
         "category": "Error",
         "code": 7005
@@ -6914,7 +6908,6 @@
         "category": "Error",
         "code": 7061
     },
-
     "You cannot rename this element.": {
         "category": "Error",
         "code": 8000
@@ -7059,7 +7052,6 @@
         "category": "Error",
         "code": 8039
     },
-
     "Declaration emit for this file requires using private name '{0}'. An explicit type annotation may unblock declaration emit.": {
         "category": "Error",
         "code": 9005
@@ -7292,7 +7284,6 @@
         "category": "Error",
         "code": 18003
     },
-
     "File is a CommonJS module; it may be converted to an ES module.": {
         "category": "Suggestion",
         "code": 80001
@@ -7333,7 +7324,6 @@
         "category": "Suggestion",
         "code": 80010
     },
-
     "Add missing 'super()' call": {
         "category": "Message",
         "code": 90001
@@ -7554,7 +7544,6 @@
         "category": "Message",
         "code": 90071
     },
-
     "Convert function to an ES2015 class": {
         "category": "Message",
         "code": 95001
@@ -8323,7 +8312,6 @@
         "category": "Message",
         "code": 95197
     },
-
     "No value exists in scope for the shorthand property '{0}'. Either declare one or provide an initializer.": {
         "category": "Error",
         "code": 18004
@@ -8520,4 +8508,4 @@
         "category": "Error",
         "code": 18061
     }
-}
+}

src/compiler/emitter.ts

@@ -646,7 +646,7 @@ export function getCommonSourceDirectory(
         commonSourceDirectory = getNormalizedAbsolutePath(options.rootDir, currentDirectory);
         checkSourceFilesBelongToPath?.(options.rootDir);
     }
-    else if (options.composite && options.configFilePath) {
+    else if (options.configFilePath) {
         // Project compilations never infer their root from the input source paths
         commonSourceDirectory = getDirectoryPath(normalizeSlashes(options.configFilePath));
         checkSourceFilesBelongToPath?.(commonSourceDirectory);
@@ -664,6 +664,23 @@ export function getCommonSourceDirectory(
     return commonSourceDirectory;
 }
 
+/** @internal */
+export function getComputedCommonSourceDirectory(
+    emittedFiles: readonly string[],
+    currentDirectory: string,
+    getCanonicalFileName: GetCanonicalFileName,
+): string {
+    let commonSourceDirectory = computeCommonSourceDirectoryOfFilenames(emittedFiles, currentDirectory, getCanonicalFileName);
+
+    if (commonSourceDirectory && commonSourceDirectory[commonSourceDirectory.length - 1] !== directorySeparator) {
+        // Make sure directory path ends with directory separator so this string can directly
+        // used to replace with "" to get the relative path of the source file and the relative path doesn't
+        // start with / making it rooted path
+        commonSourceDirectory += directorySeparator;
+    }
+    return commonSourceDirectory;
+}
+
 /** @internal */
 export function getCommonSourceDirectoryOfConfig({ options, fileNames }: ParsedCommandLine, ignoreCase: boolean): string {
     return getCommonSourceDirectory(

src/compiler/moduleNameResolver.ts

@@ -2884,7 +2884,7 @@ function getLoadModuleFromTargetExportOrImport(extensions: Extensions, state: Mo
                 const commonSourceDirGuesses: string[] = [];
                 // A `rootDir` compiler option strongly indicates the root location
                 // A `composite` project is using project references and has it's common src dir set to `.`, so it shouldn't need to check any other locations
-                if (state.compilerOptions.rootDir || (state.compilerOptions.composite && state.compilerOptions.configFilePath)) {
+                if (state.compilerOptions.rootDir || state.compilerOptions.configFilePath) {
                     const commonDir = toAbsolutePath(getCommonSourceDirectory(state.compilerOptions, () => [], state.host.getCurrentDirectory?.() || "", getCanonicalFileName));
                     commonSourceDirGuesses.push(commonDir);
                 }

src/compiler/program.ts

@@ -111,6 +111,7 @@ import {
     GetCanonicalFileName,
     getCommonSourceDirectory as ts_getCommonSourceDirectory,
     getCommonSourceDirectoryOfConfig,
+    getComputedCommonSourceDirectory,
     getDeclarationDiagnostics as ts_getDeclarationDiagnostics,
     getDefaultLibFileName,
     getDirectoryPath,
@@ -4293,6 +4294,27 @@ export function createProgram(_rootNamesOrOptions: readonly string[] | CreatePro
             }
         }
 
+        if (
+            !options.noEmit &&
+            !options.composite &&
+            !options.rootDir &&
+            options.configFilePath &&
+            (options.outDir || // there is --outDir specified
+                (getEmitDeclarations(options) && options.declarationDir)) // there is --declarationDir specified
+        ) {
+            // Check if rootDir inferred changed and issue diagnostic
+            const dir = getCommonSourceDirectory();
+            const emittedFiles = mapDefined(files, file => !file.isDeclarationFile && sourceFileMayBeEmitted(file, program) ? file.fileName : undefined);
+            const dir59 = getComputedCommonSourceDirectory(emittedFiles, currentDirectory, getCanonicalFileName);
+            if (dir59 !== "" && getCanonicalFileName(dir) !== getCanonicalFileName(dir59)) {
+                // change in layout
+                programDiagnostics.addConfigDiagnostic(createCompilerDiagnosticFromMessageChain(chainDiagnosticMessages(
+                    chainDiagnosticMessages(/*details*/ undefined, Diagnostics.Visit_https_Colon_Slash_Slashaka_ms_Slashts6_for_migration_information),
+                    Diagnostics.Inferred_common_source_directory_differs_from_tsconfig_directory_output_layout_will_be_changed,
+                )));
+            }
+        }
+
         if (options.checkJs && !getAllowJSCompilerOption(options)) {
             createDiagnosticForOptionName(Diagnostics.Option_0_cannot_be_specified_without_specifying_option_1, "checkJs", "allowJs");
         }

src/compiler/utilities.ts

@@ -6622,7 +6622,7 @@ export function sourceFileMayBeEmitted(sourceFile: SourceFile, host: SourceFileM
     // Json file is not emitted if outDir is not specified
     if (!options.outDir) return false;
     // Otherwise if rootDir or composite config file, we know common sourceDir and can check if file would be emitted in same location
-    if (options.rootDir || (options.composite && options.configFilePath)) {
+    if (options.rootDir || options.configFilePath) {
         const commonDir = getNormalizedAbsolutePath(getCommonSourceDirectory(options, () => [], host.getCurrentDirectory(), host.getCanonicalFileName), host.getCurrentDirectory());
         const outputPath = getSourceFilePathInNewDirWorker(sourceFile.fileName, options.outDir, host.getCurrentDirectory(), commonDir, host.getCanonicalFileName);
         if (comparePaths(sourceFile.fileName, outputPath, host.getCurrentDirectory(), !host.useCaseSensitiveFileNames()) === Comparison.EqualTo) return false;

src/testRunner/unittests/helpers/monorepoSymlinkedSiblingPackages.ts

@@ -151,6 +151,7 @@ function getMonorepoSymlinkedSiblingPackagesSysWithUnRelatedFolders(
             compilerOptions: {
                 outDir: "lib",
                 declaration: true,
+                rootDir: "src",
             },
             include: ["src/**/*.ts"],
         }),
@@ -169,6 +170,7 @@ function getMonorepoSymlinkedSiblingPackagesSysWithUnRelatedFolders(
             compilerOptions: {
                 outDir: "lib",
                 declaration: true,
+                rootDir: "src",
             },
             include: ["src/**/*.ts"],
         }),
@@ -183,6 +185,7 @@ function getMonorepoSymlinkedSiblingPackagesSysWithUnRelatedFolders(
         "/home/src/projects/b/2/b-impl/b/tsconfig.json": jsonToReadableText({
             compilerOptions: {
                 outDir: "lib",
+                rootDir: "src",
             },
             include: ["src/**/*.ts"],
         }),

src/testRunner/unittests/tsbuild/outputPaths.ts

@@ -26,7 +26,7 @@ describe("unittests:: tsbuild:: outputPaths::", () => {
             ...input,
         });
 
-        it("verify getOutputFileNames", () => {
+        it("verify getOutputFileNames " + input.subScenario, () => {
             const sys = input.sys();
             assert.deepEqual(
                 ts.getOutputFileNames(
@@ -58,7 +58,7 @@ describe("unittests:: tsbuild:: outputPaths::", () => {
                 }),
             }),
         edits,
-    }, ["/home/src/workspaces/project/dist/index.js"]);
+    }, ["/home/src/workspaces/project/dist/src/index.js"]);
 
     verify({
         subScenario: "when rootDir is not specified and is composite",

tests/baselines/reference/commonSourceDirectory.js

@@ -27,3 +27,35 @@ foo_1.x + bar_1.y;
 //// [/app/bin/index.d.ts]
 /// <reference path="../../types/bar.d.ts" preserve="true" />
 export {};
+
+
+//// [DtsFileErrors]
+
+
+error TS5011: Inferred common source directory differs from tsconfig directory, output layout will be changed.
+  Visit https://aka.ms/ts6 for migration information.
+
+
+!!! error TS5011: Inferred common source directory differs from tsconfig directory, output layout will be changed.
+!!! error TS5011:   Visit https://aka.ms/ts6 for migration information.
+==== /app/tsconfig.json (0 errors) ====
+    {
+        "compilerOptions": {
+            "outDir": "bin",
+            "typeRoots": ["../types"],
+            "sourceMap": true,
+            "mapRoot": "myMapRoot",
+            "sourceRoot": "mySourceRoot",
+            "declaration": true
+        }
+    }
+
+==== /app/bin/index.d.ts (0 errors) ====
+    /// <reference path="../../types/bar.d.ts" preserve="true" />
+    export {};
+
+==== /types/bar.d.ts (0 errors) ====
+    declare module "bar" {
+        export const y = 0;
+    }
+

tests/baselines/reference/commonSourceDirectory_dts.errors.txt

@@ -0,0 +1,24 @@
+error TS5011: Inferred common source directory differs from tsconfig directory, output layout will be changed.
+  Visit https://aka.ms/ts6 for migration information.
+
+
+!!! error TS5011: Inferred common source directory differs from tsconfig directory, output layout will be changed.
+!!! error TS5011:   Visit https://aka.ms/ts6 for migration information.
+==== /app/tsconfig.json (0 errors) ====
+    {
+        "compilerOptions": {
+            "outDir": "bin",
+            "sourceMap": true,
+            "mapRoot": "myMapRoot",
+            "sourceRoot": "mySourceRoot",
+            "declaration": true
+        }
+    }
+
+==== /app/lib/bar.d.ts (0 errors) ====
+    declare const y: number;
+
+==== /app/src/index.ts (0 errors) ====
+    /// <reference path="../lib/bar.d.ts" preserve="true" />
+    export const x = y;
+

tests/baselines/reference/commonSourceDirectory_dts.js

@@ -8,14 +8,14 @@ declare const y: number;
 export const x = y;
 
 
-//// [/app/bin/index.js]
+//// [/app/bin/src/index.js]
 "use strict";
 Object.defineProperty(exports, "__esModule", { value: true });
 exports.x = void 0;
 /// <reference path="../lib/bar.d.ts" preserve="true" />
 exports.x = y;
-//# sourceMappingURL=../src/myMapRoot/index.js.map
+//# sourceMappingURL=../../myMapRoot/src/index.js.map
 
-//// [/app/bin/index.d.ts]
-/// <reference path="../lib/bar.d.ts" preserve="true" />
+//// [/app/bin/src/index.d.ts]
+/// <reference path="../../lib/bar.d.ts" preserve="true" />
 export declare const x: number;