Add useCaseSensitiveFileNames to ModuleResolutionHost

...so that path comparisons can use it during module resolution.

Author: amcasey

src/compiler/moduleNameResolver.ts

@@ -280,6 +280,11 @@ namespace ts {
     }
     const nodeModulesAtTypes = combinePaths("node_modules", "@types");
 
+    function arePathsEqual(path1: string, path2: string, host: ModuleResolutionHost): boolean {
+        const useCaseSensitiveFileNames = typeof host.useCaseSensitiveFileNames === "function" ? host.useCaseSensitiveFileNames() : host.useCaseSensitiveFileNames;
+        return comparePaths(path1, path2, !useCaseSensitiveFileNames) === Comparison.EqualTo;
+    }
+
     /**
      * @param {string | undefined} containingFile - file that contains type reference directive, can be undefined if containing file is unknown.
      * This is possible in case if resolution is performed for directives specified via 'types' parameter. In this case initial path for secondary lookups
@@ -343,7 +348,7 @@ namespace ts {
             resolvedTypeReferenceDirective = {
                 primary,
                 resolvedFileName,
-                originalPath: fileName === resolvedFileName ? undefined : fileName,
+                originalPath: arePathsEqual(fileName, resolvedFileName, host) ? undefined : fileName,
                 packageId,
                 isExternalLibraryImport: pathContainsNodeModules(fileName),
             };
@@ -1072,12 +1077,6 @@ namespace ts {
         return resolvedModule.resolvedFileName;
     }
 
-    /* @internal */
-    export function tryResolveJSModule(moduleName: string, initialDir: string, host: ModuleResolutionHost): string | undefined {
-        const { resolvedModule } = tryResolveJSModuleWorker(moduleName, initialDir, host);
-        return resolvedModule && resolvedModule.resolvedFileName;
-    }
-
     const jsOnlyExtensions = [Extensions.JavaScript];
     const tsExtensions = [Extensions.TypeScript, Extensions.JavaScript];
     const tsPlusJsonExtensions = [...tsExtensions, Extensions.Json];
@@ -1118,7 +1117,7 @@ namespace ts {
                 let resolvedValue = resolved.value;
                 if (!compilerOptions.preserveSymlinks && resolvedValue && !resolvedValue.originalPath) {
                     const path = realPath(resolvedValue.path, host, traceEnabled);
-                    const originalPath = path === resolvedValue.path ? undefined : resolvedValue.path;
+                    const originalPath = arePathsEqual(path, resolvedValue.path, host) ? undefined : resolvedValue.path;
                     resolvedValue = { ...resolvedValue, path, originalPath };
                 }
                 // For node_modules lookups, get the real path so that multiple accesses to an `npm link`-ed module do not create duplicate files.

src/compiler/program.ts

@@ -3771,7 +3771,7 @@ namespace ts {
         function fileExistsIfProjectReferenceDts(file: string) {
             const source = host.getSourceOfProjectReferenceRedirect(host.toPath(file));
             return source !== undefined ?
-                isString(source) ? originalFileExists.call(host.compilerHost, source) : true :
+                isString(source) ? originalFileExists.call(host.compilerHost, source) as boolean : true :
                 undefined;
         }
 

src/compiler/types.ts

@@ -6451,6 +6451,7 @@ namespace ts {
         realpath?(path: string): string;
         getCurrentDirectory?(): string;
         getDirectories?(path: string): string[];
+        useCaseSensitiveFileNames?: boolean | (() => boolean);
     }
 
     /**

src/compiler/utilities.ts

@@ -6188,7 +6188,9 @@ namespace ts {
     }
 
     export interface SymlinkedDirectory {
+        /** Matches the casing returned by `realpath`.  Used to compute the `realpath` of children. */
         real: string;
+        /** toPath(real).  Stored to avoid repeated recomputation. */
         realPath: Path;
     }
 

src/harness/harnessLanguageService.ts

@@ -325,7 +325,8 @@ namespace Harness.LanguageService {
                     readFile: fileName => {
                         const scriptInfo = this.getScriptInfo(fileName);
                         return scriptInfo && scriptInfo.content;
-                    }
+                    },
+                    useCaseSensitiveFileNames: this.useCaseSensitiveFileNames()
                 };
                 this.getModuleResolutionsForFile = (fileName) => {
                     const scriptInfo = this.getScriptInfo(fileName)!;

src/server/project.ts

@@ -1704,6 +1704,7 @@ namespace ts.server {
                     readFile: this.projectService.host.readFile.bind(this.projectService.host),
                     getDirectories: this.projectService.host.getDirectories.bind(this.projectService.host),
                     trace: this.projectService.host.trace?.bind(this.projectService.host),
+                    useCaseSensitiveFileNames: this.program.useCaseSensitiveFileNames(),
                 };
             }
             return this.projectService.host;

src/testRunner/unittests/moduleResolution.ts

@@ -65,11 +65,12 @@ namespace ts {
                 fileExists: path => {
                     assert.isTrue(directories.has(getDirectoryPath(path)), `'fileExists' '${path}' request in non-existing directory`);
                     return map.has(path);
-                }
+                },
+                useCaseSensitiveFileNames: true
             };
         }
         else {
-            return { readFile, realpath, fileExists: path => map.has(path) };
+            return { readFile, realpath, fileExists: path => map.has(path), useCaseSensitiveFileNames: true };
         }
         function readFile(path: string): string | undefined {
             const file = map.get(path);

tests/baselines/reference/api/tsserverlibrary.d.ts

@@ -3056,6 +3056,7 @@ declare namespace ts {
         realpath?(path: string): string;
         getCurrentDirectory?(): string;
         getDirectories?(path: string): string[];
+        useCaseSensitiveFileNames?: boolean | (() => boolean);
     }
     /**
      * Represents the result of module resolution.

tests/baselines/reference/api/typescript.d.ts

@@ -3056,6 +3056,7 @@ declare namespace ts {
         realpath?(path: string): string;
         getCurrentDirectory?(): string;
         getDirectories?(path: string): string[];
+        useCaseSensitiveFileNames?: boolean | (() => boolean);
     }
     /**
      * Represents the result of module resolution.