Combine moduleHasNonRelativeName with isExternalModuleNameRelative (#16564)

Author: Andy

src/compiler/core.ts

@@ -1580,10 +1580,21 @@ namespace ts {
         return path && !isRootedDiskPath(path) && path.indexOf("://") !== -1;
     }
 
+    /* @internal */
+    export function pathIsRelative(path: string): boolean {
+        return /^\.\.?($|[\\/])/.test(path);
+    }
+
     export function isExternalModuleNameRelative(moduleName: string): boolean {
         // TypeScript 1.0 spec (April 2014): 11.2.1
         // An external module name is "relative" if the first term is "." or "..".
-        return /^\.\.?($|[\\/])/.test(moduleName);
+        // Update: We also consider a path like `C:\foo.ts` "relative" because we do not search for it in `node_modules` or treat it as an ambient module.
+        return pathIsRelative(moduleName) || isRootedDiskPath(moduleName);
+    }
+
+    /** @deprecated Use `!isExternalModuleNameRelative(moduleName)` instead. */
+    export function moduleHasNonRelativeName(moduleName: string): boolean {
+        return !isExternalModuleNameRelative(moduleName);
     }
 
     export function getEmitScriptTarget(compilerOptions: CompilerOptions) {

src/compiler/moduleNameResolver.ts

@@ -54,10 +54,6 @@ namespace ts {
         };
     }
 
-    export function moduleHasNonRelativeName(moduleName: string): boolean {
-        return !(isRootedDiskPath(moduleName) || isExternalModuleNameRelative(moduleName));
-    }
-
     interface ModuleResolutionState {
         host: ModuleResolutionHost;
         compilerOptions: CompilerOptions;
@@ -318,7 +314,7 @@ namespace ts {
         }
 
         function getOrCreateCacheForModuleName(nonRelativeModuleName: string) {
-            if (!moduleHasNonRelativeName(nonRelativeModuleName)) {
+            if (isExternalModuleNameRelative(nonRelativeModuleName)) {
                 return undefined;
             }
             let perModuleNameCache = moduleNameToDirectoryMap.get(nonRelativeModuleName);
@@ -535,7 +531,7 @@ namespace ts {
     function tryLoadModuleUsingOptionalResolutionSettings(extensions: Extensions, moduleName: string, containingDirectory: string, loader: ResolutionKindSpecificLoader,
         failedLookupLocations: Push<string>, state: ModuleResolutionState): Resolved | undefined {
 
-        if (moduleHasNonRelativeName(moduleName)) {
+        if (!isExternalModuleNameRelative(moduleName)) {
             return tryLoadModuleUsingBaseUrl(extensions, moduleName, loader, failedLookupLocations, state);
         }
         else {
@@ -711,7 +707,7 @@ namespace ts {
                 return toSearchResult({ resolved, isExternalLibraryImport: false });
             }
 
-            if (moduleHasNonRelativeName(moduleName)) {
+            if (!isExternalModuleNameRelative(moduleName)) {
                 if (traceEnabled) {
                     trace(host, Diagnostics.Loading_module_0_from_node_modules_folder_target_file_type_1, moduleName, Extensions[extensions]);
                 }
@@ -1024,7 +1020,7 @@ namespace ts {
             }
             const perModuleNameCache = cache && cache.getOrCreateCacheForModuleName(moduleName);
 
-            if (moduleHasNonRelativeName(moduleName)) {
+            if (!isExternalModuleNameRelative(moduleName)) {
                 // Climb up parent directories looking for a module.
                 const resolved = forEachAncestorDirectory(containingDirectory, directory => {
                     const resolutionFromCache = tryFindNonRelativeModuleNameInCache(perModuleNameCache, moduleName, directory, traceEnabled, host);

src/server/lsHost.ts

@@ -29,7 +29,7 @@ namespace ts.server {
                     : undefined;
                 const primaryResult = resolveModuleName(moduleName, containingFile, compilerOptions, host);
                 // return result immediately only if it is .ts, .tsx or .d.ts
-                if (moduleHasNonRelativeName(moduleName) && !(primaryResult.resolvedModule && extensionIsTypeScript(primaryResult.resolvedModule.extension)) && globalCache !== undefined) {
+                if (!isExternalModuleNameRelative(moduleName) && !(primaryResult.resolvedModule && extensionIsTypeScript(primaryResult.resolvedModule.extension)) && globalCache !== undefined) {
                     // otherwise try to load typings from @types
 
                     // create different collection of failed lookup locations for second pass

src/services/codefixes/importFixes.ts

@@ -565,7 +565,7 @@ namespace ts.codefix {
 
                 function getRelativePath(path: string, directoryPath: string) {
                     const relativePath = getRelativePathToDirectoryOrUrl(directoryPath, path, directoryPath, getCanonicalFileName, /*isAbsolutePathAnUrl*/ false);
-                    return moduleHasNonRelativeName(relativePath) ? "./" + relativePath : relativePath;
+                    return !pathIsRelative(relativePath) ? "./" + relativePath : relativePath;
                 }
             }