Add importMappings ToStringOpts

src/Code.ts

@@ -22,6 +22,8 @@ export interface ToStringOpts {
   prefix?: string;
   /** Optional per-file overrides for the prettier config, i.e. to use longer-than-normal line lengths. */
   prettierOverrides?: Options;
+  /** optional importMappings */
+  importMappings?: { [key: string]: string };
 }
 
 export class Code extends Node {
@@ -40,7 +42,7 @@ export class Code extends Node {
    * to return a `Promise<String>`.
    */
   toStringWithImports(opts?: ToStringOpts): Promise<string> {
-    const { path = '', forceDefaultImport, forceModuleImport, prefix, prettierOverrides = {} } = opts || {};
+    const { path = '', forceDefaultImport, forceModuleImport, prefix, prettierOverrides = {}, importMappings = {} } = opts || {};
     const ourModulePath = path.replace(/\.[tj]sx?/, '');
     if (forceDefaultImport || forceModuleImport) {
       this.deepReplaceNamedImports(forceDefaultImport || [], forceModuleImport || []);
@@ -49,7 +51,7 @@ export class Code extends Node {
     const imports = this.deepFindImports();
     const defs = this.deepFindDefs();
     assignAliasesIfNeeded(defs, imports, ourModulePath);
-    const importPart = emitImports(imports, ourModulePath);
+    const importPart = emitImports(imports, ourModulePath, importMappings);
     const bodyPart = this.generateCode();
     const maybePrefix = prefix ? `${prefix}\n` : '';
     return maybePrettyWithConfig(maybePrefix + importPart + '\n' + bodyPart, prettierOverrides);

src/Import-tests.ts

@@ -145,6 +145,20 @@ describe('Import', () => {
     expect(maybeRelativePath('zaz/Zaz', './foo/Foo')).toEqual('../foo/Foo');
   });
 
+  it('can interpret importMappings', () => {
+    const parsed = Import.from('Empty@./google/protobuf/empty');
+    expect(parsed).toBeInstanceOf(ImportsName);
+
+    const sym = parsed as ImportsName;
+    expect(sym.symbol).toEqual('Empty');
+    expect(sym.source).toEqual('./google/protobuf/empty');
+
+    const importMappings = { './google/protobuf/empty': './external/protoapis/google/protobuf/empty' }
+    expect(emit(sym, importMappings)).toMatchInlineSnapshot(
+      `"import { Empty } from './external/protoapis/google/protobuf/empty';"`
+    );
+  });
+
   it('can handle relative imports with a current directory', () => {
     expect(maybeRelativePath('./zaz/Zaz', './foo/Foo')).toEqual('../foo/Foo');
   });
@@ -174,7 +188,7 @@ describe('Import', () => {
     );
   });
 
-  function emit(spec: Import): string {
-    return emitImports([spec], '').trim();
+  function emit(spec: Import, importMappings = {}): string {
+    return emitImports([spec], '', importMappings).trim();
   }
 });

src/Import.ts

@@ -286,7 +286,7 @@ export class SideEffect extends Imported {
 }
 
 /** Generates the `import ...` lines for the given `imports`. */
-export function emitImports(imports: Import[], ourModulePath: string): string {
+export function emitImports(imports: Import[], ourModulePath: string, importMappings: { [key: string]: string }): string {
   if (imports.length == 0) {
     return '';
   }
@@ -312,6 +312,9 @@ export function emitImports(imports: Import[], ourModulePath: string): string {
     if (sameModule(ourModulePath, modulePath)) {
       return;
     }
+    if (modulePath in importMappings) {
+      modulePath = importMappings[modulePath];
+    }
     const importPath = maybeRelativePath(ourModulePath, modulePath);
 
     // Output star imports individually