Add "preserveSymlinks" option (microsoft#16661)

* Add "preserveSymlinks" option

* Respond to PR comments

Author: Andy

src/compiler/commandLineParser.ts

@@ -340,7 +340,6 @@ namespace ts {
             isTSConfigOnly: true,
             category: Diagnostics.Module_Resolution_Options,
             description: Diagnostics.A_series_of_entries_which_re_map_imports_to_lookup_locations_relative_to_the_baseUrl
-
         },
         {
             // this option can only be specified in tsconfig.json
@@ -384,6 +383,12 @@ namespace ts {
             category: Diagnostics.Module_Resolution_Options,
             description: Diagnostics.Allow_default_imports_from_modules_with_no_default_export_This_does_not_affect_code_emit_just_typechecking
         },
+        {
+            name: "preserveSymlinks",
+            type: "boolean",
+            category: Diagnostics.Module_Resolution_Options,
+            description: Diagnostics.Do_not_resolve_the_real_path_of_symlinks,
+        },
 
         // Source Maps
         {

src/compiler/diagnosticMessages.json

@@ -2662,6 +2662,10 @@
         "category": "Message",
         "code": 6012
     },
+    "Do not resolve the real path of symlinks.": {
+        "category": "Message",
+        "code": 6013
+    },
     "Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', or 'ESNEXT'.": {
         "category": "Message",
         "code": 6015

src/compiler/moduleNameResolver.ts

@@ -200,7 +200,10 @@ namespace ts {
 
         let resolvedTypeReferenceDirective: ResolvedTypeReferenceDirective | undefined;
         if (resolved) {
-            resolved = realpath(resolved, host, traceEnabled);
+            if (!options.preserveSymlinks) {
+                resolved = realpath(resolved, host, traceEnabled);
+            }
+
             if (traceEnabled) {
                 trace(host, Diagnostics.Type_reference_directive_0_was_successfully_resolved_to_1_primary_Colon_2, typeReferenceDirectiveName, resolved, primary);
             }
@@ -734,8 +737,14 @@ namespace ts {
                     trace(host, Diagnostics.Loading_module_0_from_node_modules_folder_target_file_type_1, moduleName, Extensions[extensions]);
                 }
                 const resolved = loadModuleFromNodeModules(extensions, moduleName, containingDirectory, failedLookupLocations, state, cache);
+                if (!resolved) return undefined;
+
+                let resolvedValue = resolved.value;
+                if (!compilerOptions.preserveSymlinks) {
+                    resolvedValue = resolvedValue && { ...resolved.value, path: realpath(resolved.value.path, host, traceEnabled), extension: resolved.value.extension };
+                }
                 // For node_modules lookups, get the real path so that multiple accesses to an `npm link`-ed module do not create duplicate files.
-                return resolved && { value: resolved.value && { resolved: { ...resolved.value, path: realpath(resolved.value.path, host, traceEnabled) }, isExternalLibraryImport: true } };
+                return { value: resolvedValue && { resolved: resolvedValue, isExternalLibraryImport: true } };
             }
             else {
                 const candidate = normalizePath(combinePaths(containingDirectory, moduleName));

src/compiler/types.ts

@@ -3608,6 +3608,7 @@ namespace ts {
         paths?: MapLike<string[]>;
         /*@internal*/ plugins?: PluginImport[];
         preserveConstEnums?: boolean;
+        preserveSymlinks?: boolean;
         project?: string;
         /* @internal */ pretty?: DiagnosticStyle;
         reactNamespace?: string;
@@ -3923,6 +3924,10 @@ namespace ts {
         readFile(fileName: string): string | undefined;
         trace?(s: string): void;
         directoryExists?(directoryName: string): boolean;
+        /**
+         * Resolve a symbolic link.
+         * @see https://nodejs.org/api/fs.html#fs_fs_realpathsync_path_options
+         */
         realpath?(path: string): string;
         getCurrentDirectory?(): string;
         getDirectories?(path: string): string[];

src/harness/unittests/moduleResolution.ts

@@ -26,10 +26,19 @@ namespace ts {
     interface File {
         name: string;
         content?: string;
+        symlinks?: string[];
     }
 
     function createModuleResolutionHost(hasDirectoryExists: boolean, ...files: File[]): ModuleResolutionHost {
-        const map = arrayToMap(files, f => f.name);
+        const map = createMap<File>();
+        for (const file of files) {
+            map.set(file.name, file);
+            if (file.symlinks) {
+                for (const symlink of file.symlinks) {
+                    map.set(symlink, file);
+                }
+            }
+        }
 
         if (hasDirectoryExists) {
             const directories = createMap<string>();
@@ -46,6 +55,7 @@ namespace ts {
             }
             return {
                 readFile,
+                realpath,
                 directoryExists: path => directories.has(path),
                 fileExists: path => {
                     assert.isTrue(directories.has(getDirectoryPath(path)), `'fileExists' '${path}' request in non-existing directory`);
@@ -54,12 +64,15 @@ namespace ts {
             };
         }
         else {
-            return { readFile, fileExists: path => map.has(path) };
+            return { readFile, realpath, fileExists: path => map.has(path) };
         }
         function readFile(path: string): string | undefined {
             const file = map.get(path);
             return file && file.content;
         }
+        function realpath(path: string): string {
+            return map.get(path).name;
+        }
     }
 
     describe("Node module resolution - relative paths", () => {
@@ -233,8 +246,8 @@ namespace ts {
             test(/*hasDirectoryExists*/ true);
 
             function test(hasDirectoryExists: boolean) {
-                const containingFile = { name: "/a/node_modules/b/c/node_modules/d/e.ts" };
-                const moduleFile = { name: "/a/node_modules/foo/index.d.ts" };
+                const containingFile: File = { name: "/a/node_modules/b/c/node_modules/d/e.ts" };
+                const moduleFile: File = { name: "/a/node_modules/foo/index.d.ts" };
                 const resolution = nodeModuleNameResolver("foo", containingFile.name, {}, createModuleResolutionHost(hasDirectoryExists, containingFile, moduleFile));
                 checkResolvedModuleWithFailedLookupLocations(resolution, createResolvedModule(moduleFile.name, /*isExternalLibraryImport*/ true), [
                     "/a/node_modules/b/c/node_modules/d/node_modules/foo.ts",
@@ -289,6 +302,19 @@ namespace ts {
                 ]);
             }
         });
+
+        testPreserveSymlinks(/*preserveSymlinks*/ false);
+        testPreserveSymlinks(/*preserveSymlinks*/ true);
+        function testPreserveSymlinks(preserveSymlinks: boolean) {
+            it(`preserveSymlinks: ${preserveSymlinks}`, () => {
+                const realFileName = "/linked/index.d.ts";
+                const symlinkFileName = "/app/node_modulex/linked/index.d.ts";
+                const host = createModuleResolutionHost(/*hasDirectoryExists*/ true, { name: realFileName, symlinks: [symlinkFileName] });
+                const resolution = nodeModuleNameResolver("linked", "/app/app.ts", { preserveSymlinks }, host);
+                const resolvedFileName = preserveSymlinks ? symlinkFileName : realFileName;
+                checkResolvedModule(resolution.resolvedModule, { resolvedFileName, isExternalLibraryImport: true, extension: Extension.Dts });
+            });
+        }
     });
 
     describe("Module resolution - relative imports", () => {

src/server/protocol.ts

@@ -2429,6 +2429,7 @@ namespace ts.server.protocol {
         paths?: MapLike<string[]>;
         plugins?: PluginImport[];
         preserveConstEnums?: boolean;
+        preserveSymlinks?: boolean;
         project?: string;
         reactNamespace?: string;
         removeComments?: boolean;

tests/baselines/reference/moduleResolutionWithSymlinks_preserveSymlinks.errors.txt

@@ -0,0 +1,25 @@
+/app/app.ts(9,1): error TS90010: Type 'C' is not assignable to type 'C'. Two different types with this name exist, but they are unrelated.
+  Types have separate declarations of a private property 'x'.
+
+
+==== /app/app.ts (1 errors) ====
+    // We shouldn't resolve symlinks for references either. See the trace.
+    /// <reference types="linked" />
+    
+    import { C as C1 } from "linked";
+    import { C as C2 } from "linked2";
+    
+    let x = new C1();
+    // Should fail. We no longer resolve any symlinks.
+    x = new C2();
+    ~
+!!! error TS90010: Type 'C' is not assignable to type 'C'. Two different types with this name exist, but they are unrelated.
+!!! error TS90010:   Types have separate declarations of a private property 'x'.
+    
+==== /linked/index.d.ts (0 errors) ====
+    export { real } from "real";
+    export class C { private x; }
+    
+==== /app/node_modules/real/index.d.ts (0 errors) ====
+    export const real: string;
+    

tests/baselines/reference/moduleResolutionWithSymlinks_preserveSymlinks.js

@@ -0,0 +1,31 @@
+//// [tests/cases/compiler/moduleResolutionWithSymlinks_preserveSymlinks.ts] ////
+
+//// [index.d.ts]
+export { real } from "real";
+export class C { private x; }
+
+//// [index.d.ts]
+export const real: string;
+
+//// [app.ts]
+// We shouldn't resolve symlinks for references either. See the trace.
+/// <reference types="linked" />
+
+import { C as C1 } from "linked";
+import { C as C2 } from "linked2";
+
+let x = new C1();
+// Should fail. We no longer resolve any symlinks.
+x = new C2();
+
+
+//// [app.js]
+"use strict";
+// We shouldn't resolve symlinks for references either. See the trace.
+/// <reference types="linked" />
+exports.__esModule = true;
+var linked_1 = require("linked");
+var linked2_1 = require("linked2");
+var x = new linked_1.C();
+// Should fail. We no longer resolve any symlinks.
+x = new linked2_1.C();

tests/baselines/reference/moduleResolutionWithSymlinks_preserveSymlinks.trace.json

@@ -0,0 +1,55 @@
+[
+    "======== Resolving type reference directive 'linked', containing file '/app/app.ts', root directory not set. ========",
+    "Root directory cannot be determined, skipping primary search paths.",
+    "Looking up in 'node_modules' folder, initial location '/app'.",
+    "File '/app/node_modules/linked.d.ts' does not exist.",
+    "File '/app/node_modules/linked/package.json' does not exist.",
+    "File '/app/node_modules/linked/index.d.ts' exist - use it as a name resolution result.",
+    "======== Type reference directive 'linked' was successfully resolved to '/app/node_modules/linked/index.d.ts', primary: false. ========",
+    "======== Resolving module 'real' from '/app/node_modules/linked/index.d.ts'. ========",
+    "Explicitly specified module resolution kind: 'NodeJs'.",
+    "Loading module 'real' from 'node_modules' folder, target file type 'TypeScript'.",
+    "Directory '/app/node_modules/linked/node_modules' does not exist, skipping all lookups in it.",
+    "File '/app/node_modules/real.ts' does not exist.",
+    "File '/app/node_modules/real.tsx' does not exist.",
+    "File '/app/node_modules/real.d.ts' does not exist.",
+    "File '/app/node_modules/real/package.json' does not exist.",
+    "File '/app/node_modules/real/index.ts' does not exist.",
+    "File '/app/node_modules/real/index.tsx' does not exist.",
+    "File '/app/node_modules/real/index.d.ts' exist - use it as a name resolution result.",
+    "======== Module name 'real' was successfully resolved to '/app/node_modules/real/index.d.ts'. ========",
+    "======== Resolving module 'linked' from '/app/app.ts'. ========",
+    "Explicitly specified module resolution kind: 'NodeJs'.",
+    "Loading module 'linked' from 'node_modules' folder, target file type 'TypeScript'.",
+    "File '/app/node_modules/linked.ts' does not exist.",
+    "File '/app/node_modules/linked.tsx' does not exist.",
+    "File '/app/node_modules/linked.d.ts' does not exist.",
+    "File '/app/node_modules/linked/package.json' does not exist.",
+    "File '/app/node_modules/linked/index.ts' does not exist.",
+    "File '/app/node_modules/linked/index.tsx' does not exist.",
+    "File '/app/node_modules/linked/index.d.ts' exist - use it as a name resolution result.",
+    "======== Module name 'linked' was successfully resolved to '/app/node_modules/linked/index.d.ts'. ========",
+    "======== Resolving module 'linked2' from '/app/app.ts'. ========",
+    "Explicitly specified module resolution kind: 'NodeJs'.",
+    "Loading module 'linked2' from 'node_modules' folder, target file type 'TypeScript'.",
+    "File '/app/node_modules/linked2.ts' does not exist.",
+    "File '/app/node_modules/linked2.tsx' does not exist.",
+    "File '/app/node_modules/linked2.d.ts' does not exist.",
+    "File '/app/node_modules/linked2/package.json' does not exist.",
+    "File '/app/node_modules/linked2/index.ts' does not exist.",
+    "File '/app/node_modules/linked2/index.tsx' does not exist.",
+    "File '/app/node_modules/linked2/index.d.ts' exist - use it as a name resolution result.",
+    "======== Module name 'linked2' was successfully resolved to '/app/node_modules/linked2/index.d.ts'. ========",
+    "======== Resolving module 'real' from '/app/node_modules/linked2/index.d.ts'. ========",
+    "Explicitly specified module resolution kind: 'NodeJs'.",
+    "Loading module 'real' from 'node_modules' folder, target file type 'TypeScript'.",
+    "Directory '/app/node_modules/linked2/node_modules' does not exist, skipping all lookups in it.",
+    "File '/app/node_modules/real.ts' does not exist.",
+    "File '/app/node_modules/real.tsx' does not exist.",
+    "File '/app/node_modules/real.d.ts' does not exist.",
+    "File '/app/node_modules/real/package.json' does not exist.",
+    "File '/app/node_modules/real/index.ts' does not exist.",
+    "File '/app/node_modules/real/index.tsx' does not exist.",
+    "File '/app/node_modules/real/index.d.ts' exist - use it as a name resolution result.",
+    "======== Module name 'real' was successfully resolved to '/app/node_modules/real/index.d.ts'. ========"
+]

tests/baselines/reference/tsConfig/Default initialized TSConfig/tsconfig.json

@@ -39,6 +39,7 @@
     // "typeRoots": [],                       /* List of folders to include type definitions from. */
     // "types": [],                           /* Type declaration files to be included in compilation. */
     // "allowSyntheticDefaultImports": true,  /* Allow default imports from modules with no default export. This does not affect code emit, just typechecking. */
+    // "preserveSymlinks": true,              /* Do not resolve the real path of symlinks. */
 
     /* Source Map Options */
     // "sourceRoot": "./",                    /* Specify the location where debugger should locate TypeScript files instead of source locations. */