refactor(ivy): change ImportMode enum to ImportFlags (#34649)

Previously, `ReferenceEmitter.emit()` took an `ImportMode` enum value, where
one value of the enum allowed forcing new imports to be generated when
emitting a reference to some value or type.

This commit refactors `ImportMode` to be an `ImportFlags` value instead.
Using a bit field of flags will allow future customization of reference
emitting.

PR Close #34649

packages/compiler-cli/src/ngtsc/annotations/src/util.ts

@@ -10,7 +10,7 @@ import {Expression, ExternalExpr, R3DependencyMetadata, R3Reference, R3ResolvedD
 import * as ts from 'typescript';
 
 import {ErrorCode, FatalDiagnosticError, makeDiagnostic} from '../../diagnostics';
-import {DefaultImportRecorder, ImportMode, Reference, ReferenceEmitter} from '../../imports';
+import {DefaultImportRecorder, ImportFlags, Reference, ReferenceEmitter} from '../../imports';
 import {ForeignFunctionResolver, PartialEvaluator} from '../../partial_evaluator';
 import {ClassDeclaration, CtorParameter, Decorator, Import, ReflectionHost, TypeValueReference, isNamedClassDeclaration} from '../../reflection';
 import {DeclarationData} from '../../scope';
@@ -189,8 +189,8 @@ export function validateConstructorDependencies(
 export function toR3Reference(
     valueRef: Reference, typeRef: Reference, valueContext: ts.SourceFile,
     typeContext: ts.SourceFile, refEmitter: ReferenceEmitter): R3Reference {
-  const value = refEmitter.emit(valueRef, valueContext, ImportMode.UseExistingImport);
-  const type = refEmitter.emit(typeRef, typeContext, ImportMode.ForceNewImport);
+  const value = refEmitter.emit(valueRef, valueContext);
+  const type = refEmitter.emit(typeRef, typeContext, ImportFlags.ForceNewImport);
   if (value === null || type === null) {
     throw new Error(`Could not refer to ${ts.SyntaxKind[valueRef.node.kind]}`);
   }

packages/compiler-cli/src/ngtsc/imports/index.ts

@@ -11,5 +11,5 @@ export {ImportRewriter, NoopImportRewriter, R3SymbolsImportRewriter, validateAnd
 export {DefaultImportRecorder, DefaultImportTracker, NOOP_DEFAULT_IMPORT_RECORDER} from './src/default';
 export {AbsoluteModuleStrategy, FileToModuleHost, FileToModuleStrategy, LocalIdentifierStrategy, LogicalProjectStrategy, ReferenceEmitStrategy, ReferenceEmitter, RelativePathStrategy} from './src/emitter';
 export {Reexport} from './src/reexport';
-export {ImportMode, OwningModule, Reference} from './src/references';
+export {ImportFlags, OwningModule, Reference} from './src/references';
 export {ModuleResolver} from './src/resolver';

packages/compiler-cli/src/ngtsc/imports/src/alias.ts

@@ -10,8 +10,10 @@ import {Expression, ExternalExpr} from '@angular/compiler';
 import * as ts from 'typescript';
 
 import {ClassDeclaration, ReflectionHost, isNamedClassDeclaration} from '../../reflection';
-import {FileToModuleHost, ReferenceEmitStrategy} from './emitter';
-import {ImportMode, Reference} from './references';
+
+import {FileToModuleHost, ImportFlags, ReferenceEmitStrategy} from './emitter';
+import {Reference} from './references';
+
 
 // Escape anything that isn't alphanumeric, '/' or '_'.
 const CHARS_TO_ESCAPE = /[^a-zA-Z0-9/_]/g;
@@ -206,7 +208,7 @@ export class PrivateExportAliasingHost implements AliasingHost {
  * directive or pipe, if it exists.
  */
 export class AliasStrategy implements ReferenceEmitStrategy {
-  emit(ref: Reference<ts.Node>, context: ts.SourceFile, importMode: ImportMode): Expression|null {
+  emit(ref: Reference<ts.Node>, context: ts.SourceFile, importMode: ImportFlags): Expression|null {
     return ref.alias;
   }
 }

packages/compiler-cli/src/ngtsc/imports/src/emitter.ts

@@ -14,7 +14,7 @@ import {ReflectionHost} from '../../reflection';
 import {getSourceFile, isDeclaration, nodeNameForError} from '../../util/src/typescript';
 
 import {findExportedNameOfNode} from './find_export';
-import {ImportMode, Reference} from './references';
+import {Reference} from './references';
 import {ModuleResolver} from './resolver';
 
 
@@ -29,6 +29,21 @@ export interface FileToModuleHost {
   fileNameToModuleName(importedFilePath: string, containingFilePath: string): string;
 }
 
+/**
+ * Flags which alter the imports generated by the `ReferenceEmitter`.
+ */
+export enum ImportFlags {
+  None = 0x00,
+
+  /**
+   * Force the generation of a new import when generating a reference, even if an identifier already
+   * exists in the target file which could be used instead.
+   *
+   * This is sometimes required if there's a risk TypeScript might remove imports during emit.
+   */
+  ForceNewImport = 0x01,
+}
+
 /**
  * A particular strategy for generating an expression which refers to a `Reference`.
  *
@@ -51,7 +66,7 @@ export interface ReferenceEmitStrategy {
    * @param importMode a flag which controls whether imports should be generated or not
    * @returns an `Expression` which refers to the `Reference`, or `null` if none can be generated
    */
-  emit(ref: Reference, context: ts.SourceFile, importMode: ImportMode): Expression|null;
+  emit(ref: Reference, context: ts.SourceFile, importFlags: ImportFlags): Expression|null;
 }
 
 /**
@@ -63,11 +78,10 @@ export interface ReferenceEmitStrategy {
 export class ReferenceEmitter {
   constructor(private strategies: ReferenceEmitStrategy[]) {}
 
-  emit(
-      ref: Reference, context: ts.SourceFile,
-      importMode: ImportMode = ImportMode.UseExistingImport): Expression {
+  emit(ref: Reference, context: ts.SourceFile, importFlags: ImportFlags = ImportFlags.None):
+      Expression {
     for (const strategy of this.strategies) {
-      const emitted = strategy.emit(ref, context, importMode);
+      const emitted = strategy.emit(ref, context, importFlags);
       if (emitted !== null) {
         return emitted;
       }
@@ -82,10 +96,10 @@ export class ReferenceEmitter {
  * such identifiers are available.
  */
 export class LocalIdentifierStrategy implements ReferenceEmitStrategy {
-  emit(ref: Reference<ts.Node>, context: ts.SourceFile, importMode: ImportMode): Expression|null {
+  emit(ref: Reference<ts.Node>, context: ts.SourceFile, importFlags: ImportFlags): Expression|null {
     // If the emitter has specified ForceNewImport, then LocalIdentifierStrategy should not use a
     // local identifier at all, *except* in the source file where the node is actually declared.
-    if (importMode === ImportMode.ForceNewImport &&
+    if (importFlags & ImportFlags.ForceNewImport &&
         getSourceFile(ref.node) !== getSourceFile(context)) {
       return null;
     }
@@ -121,7 +135,7 @@ export class AbsoluteModuleStrategy implements ReferenceEmitStrategy {
       protected program: ts.Program, protected checker: ts.TypeChecker,
       protected moduleResolver: ModuleResolver, private reflectionHost: ReflectionHost) {}
 
-  emit(ref: Reference<ts.Node>, context: ts.SourceFile, importMode: ImportMode): Expression|null {
+  emit(ref: Reference<ts.Node>, context: ts.SourceFile): Expression|null {
     if (ref.bestGuessOwningModule === null) {
       // There is no module name available for this Reference, meaning it was arrived at via a
       // relative path.

packages/compiler-cli/src/ngtsc/imports/src/references.ts

@@ -11,11 +11,6 @@ import * as ts from 'typescript';
 
 import {identifierOfNode} from '../../util/src/typescript';
 
-export enum ImportMode {
-  UseExistingImport,
-  ForceNewImport,
-}
-
 export interface OwningModule {
   specifier: string;
   resolutionContext: string;

packages/compiler-cli/src/ngtsc/modulewithproviders/src/scanner.ts

@@ -9,7 +9,7 @@
 import {ExpressionType, ExternalExpr, R3Identifiers as Identifiers, Type} from '@angular/compiler';
 import * as ts from 'typescript';
 
-import {ImportMode, Reference, ReferenceEmitter} from '../../imports';
+import {ImportFlags, Reference, ReferenceEmitter} from '../../imports';
 import {PartialEvaluator, ResolvedValueMap} from '../../partial_evaluator';
 import {ReflectionHost} from '../../reflection';
 
@@ -98,7 +98,7 @@ export class ModuleWithProvidersScanner {
     }
 
     const ngModuleExpr =
-        this.emitter.emit(ngModule, decl.getSourceFile(), ImportMode.ForceNewImport);
+        this.emitter.emit(ngModule, decl.getSourceFile(), ImportFlags.ForceNewImport);
     const ngModuleType = new ExpressionType(ngModuleExpr);
     const mwpNgType = new ExpressionType(
         new ExternalExpr(Identifiers.ModuleWithProviders), /* modifiers */ null, [ngModuleType]);