[api-extractor] API Extractor now properly runs on projects with tsconfig path mappings.

apps/api-extractor/src/analyzer/ExportAnalyzer.ts

@@ -77,6 +77,10 @@ export class ExportAnalyzer {
   private readonly _astImportsByKey: Map<string, AstImport> = new Map<string, AstImport>();
   private readonly _astNamespaceImportByModule: Map<AstModule, AstNamespaceImport> = new Map();
 
+  // Used and populated by `_hasPathMappingMatch`.
+  private readonly _exactPathMappings: Set<string> = new Set<string>();
+  private readonly _prefixPathMappings: string[] = [];
+
   public constructor(
     program: ts.Program,
     typeChecker: ts.TypeChecker,
@@ -273,12 +277,18 @@ export class ExportAnalyzer {
    * - NO:  `./file1`
    * - YES: `library1/path/path`
    * - YES: `@my-scope/my-package`
+   * - NO:  `@my-scope/my-package` (if present in tsconfig `paths` mapping).
    */
   private _isExternalModulePath(moduleSpecifier: string): boolean {
     if (ts.isExternalModuleNameRelative(moduleSpecifier)) {
       return false;
     }
 
+    // Any module specifiers that match a path mapping entry are considered part of the current package.
+    if (this._hasPathMappingMatch(moduleSpecifier)) {
+      return false;
+    }
+
     const match: RegExpExecArray | null = ExportAnalyzer._modulePathRegExp.exec(moduleSpecifier);
     if (match) {
       // Extract "@my-scope/my-package" from "@my-scope/my-package/path/module"
@@ -291,6 +301,40 @@ export class ExportAnalyzer {
     return true;
   }
 
+  /**
+   * Returns true if the module specifier matches a path mapping entry in the tsconfig `paths` map.
+   *
+   * @remarks
+   * Handles two types of path mappings:
+   *
+   * - Simple path-like strings: `some/path/to/import`
+   * - Paths with wildcards at the end: `some/path/to/*`
+   */
+  private _hasPathMappingMatch(moduleSpecifier: string): boolean {
+    // If there are no path mappings, there cannot be a match.
+    const pathKeys: string[] = Object.keys(this._program.getCompilerOptions().paths || {});
+    if (pathKeys.length === 0) {
+      return false;
+    }
+
+    // Otherwise, if we haven't already, initialize some data structures to optimize how we evaluate path
+    // mapping matches. This will only be run once for all calls of `_hasPathMappingMatch`.
+    if (this._exactPathMappings.size === 0 && this._prefixPathMappings.length === 0) {
+      for (const pathKey of pathKeys) {
+        if (pathKey.endsWith('*')) {
+          this._prefixPathMappings.push(pathKey.slice(0, -1));
+        } else {
+          this._exactPathMappings.add(pathKey);
+        }
+      }
+    }
+
+    return (
+      this._exactPathMappings.has(moduleSpecifier) ||
+      this._prefixPathMappings.some((prefix) => moduleSpecifier.startsWith(prefix))
+    );
+  }
+
   /**
    * Returns true if when we analyzed sourceFile, we found that it contains an "export=" statement that allows
    * it to behave /either/ as an ambient module /or/ as a regular importable module.  In this case,

build-tests/api-extractor-scenarios/config/build-config.json

@@ -34,6 +34,7 @@
     "inconsistentReleaseTags",
     "internationalCharacters",
     "namedDefaultImport",
+    "pathMappings",
     "preapproved",
     "spanSorting",
     "typeOf",