feat(language-service): support autocomplete string literal union types in templates (#42729)

The native TS language service has the ability to provide autocompletions for
string literal union types. This pr is for Angular to do the same in templates.

Fixes https://github.com/angular/vscode-ng-language-service/issues/1096

PR Close #42729

packages/compiler-cli/src/ngtsc/typecheck/api/checker.ts

@@ -6,8 +6,9 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {AST, MethodCall, ParseError, ParseSourceSpan, PropertyRead, SafeMethodCall, SafePropertyRead, TmplAstElement, TmplAstNode, TmplAstTemplate} from '@angular/compiler';
+import {AST, LiteralPrimitive, MethodCall, ParseError, ParseSourceSpan, PropertyRead, SafeMethodCall, SafePropertyRead, TmplAstElement, TmplAstNode, TmplAstTemplate} from '@angular/compiler';
 import {AbsoluteFsPath} from '@angular/compiler-cli/src/ngtsc/file_system';
+import {TextAttribute} from '@angular/compiler/src/render3/r3_ast';
 import * as ts from 'typescript';
 import {ErrorCode} from '../../diagnostics';
 
@@ -119,6 +120,14 @@ export interface TemplateTypeChecker {
       expr: PropertyRead|SafePropertyRead|MethodCall|SafeMethodCall,
       component: ts.ClassDeclaration): ShimLocation|null;
 
+  /**
+   * For the given node represents a `LiteralPrimitive`(the `TextAttribute` represents a string
+   * literal), retrieve a `ShimLocation` that can be used to perform autocompletion at that point in
+   * the node, if such a location exists.
+   */
+  getLiteralCompletionLocation(
+      strNode: LiteralPrimitive|TextAttribute, component: ts.ClassDeclaration): ShimLocation|null;
+
   /**
    * Get basic metadata on the directives which are in scope for the given component.
    */

packages/compiler-cli/src/ngtsc/typecheck/src/checker.ts

@@ -6,7 +6,8 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {AST, CssSelector, DomElementSchemaRegistry, MethodCall, ParseError, ParseSourceSpan, parseTemplate, PropertyRead, SafeMethodCall, SafePropertyRead, TmplAstElement, TmplAstNode, TmplAstReference, TmplAstTemplate, TmplAstVariable} from '@angular/compiler';
+import {AST, CssSelector, DomElementSchemaRegistry, LiteralPrimitive, MethodCall, ParseError, ParseSourceSpan, parseTemplate, PropertyRead, SafeMethodCall, SafePropertyRead, TmplAstElement, TmplAstNode, TmplAstReference, TmplAstTemplate, TmplAstVariable} from '@angular/compiler';
+import {TextAttribute} from '@angular/compiler/src/render3/r3_ast';
 import * as ts from 'typescript';
 import {ErrorCode} from '../../diagnostics';
 
@@ -280,6 +281,16 @@ export class TemplateTypeCheckerImpl implements TemplateTypeChecker {
         PerfPhase.TtcAutocompletion, () => engine.getExpressionCompletionLocation(ast));
   }
 
+  getLiteralCompletionLocation(
+      node: LiteralPrimitive|TextAttribute, component: ts.ClassDeclaration): ShimLocation|null {
+    const engine = this.getOrCreateCompletionEngine(component);
+    if (engine === null) {
+      return null;
+    }
+    return this.perf.inPhase(
+        PerfPhase.TtcAutocompletion, () => engine.getLiteralCompletionLocation(node));
+  }
+
   invalidateClass(clazz: ts.ClassDeclaration): void {
     this.completionCache.delete(clazz);
     this.symbolBuilderCache.delete(clazz);

packages/compiler-cli/src/ngtsc/typecheck/src/completion.ts

@@ -7,7 +7,8 @@
  */
 
 import {TmplAstReference, TmplAstTemplate} from '@angular/compiler';
-import {AST, EmptyExpr, MethodCall, PropertyRead, PropertyWrite, SafeMethodCall, SafePropertyRead, TmplAstNode} from '@angular/compiler/src/compiler';
+import {AST, EmptyExpr, LiteralPrimitive, MethodCall, PropertyRead, PropertyWrite, SafeMethodCall, SafePropertyRead, TmplAstNode} from '@angular/compiler/src/compiler';
+import {TextAttribute} from '@angular/compiler/src/render3/r3_ast';
 import * as ts from 'typescript';
 
 import {AbsoluteFsPath} from '../../file_system';
@@ -32,8 +33,9 @@ export class CompletionEngine {
   private templateContextCache =
       new Map<TmplAstTemplate|null, Map<string, ReferenceCompletion|VariableCompletion>>();
 
-  private expressionCompletionCache =
-      new Map<PropertyRead|SafePropertyRead|MethodCall|SafeMethodCall, ShimLocation>();
+  private expressionCompletionCache = new Map<
+      PropertyRead|SafePropertyRead|MethodCall|SafeMethodCall|LiteralPrimitive|TextAttribute,
+      ShimLocation>();
 
 
   constructor(private tcb: ts.Node, private data: TemplateData, private shimPath: AbsoluteFsPath) {
@@ -144,6 +146,46 @@ export class CompletionEngine {
     return res;
   }
 
+  getLiteralCompletionLocation(expr: LiteralPrimitive|TextAttribute): ShimLocation|null {
+    if (this.expressionCompletionCache.has(expr)) {
+      return this.expressionCompletionCache.get(expr)!;
+    }
+
+    let tsExpr: ts.StringLiteral|ts.NumericLiteral|null = null;
+
+    if (expr instanceof TextAttribute) {
+      const strNode = findFirstMatchingNode(this.tcb, {
+        filter: ts.isParenthesizedExpression,
+        withSpan: expr.sourceSpan,
+      });
+      if (strNode !== null && ts.isStringLiteral(strNode.expression)) {
+        tsExpr = strNode.expression;
+      }
+    } else {
+      tsExpr = findFirstMatchingNode(this.tcb, {
+        filter: (n: ts.Node): n is ts.NumericLiteral | ts.StringLiteral =>
+            ts.isStringLiteral(n) || ts.isNumericLiteral(n),
+        withSpan: expr.sourceSpan,
+      });
+    }
+
+    if (tsExpr === null) {
+      return null;
+    }
+
+    let positionInShimFile = tsExpr.getEnd();
+    if (ts.isStringLiteral(tsExpr)) {
+      // In the shimFile, if `tsExpr` is a string, the position should be in the quotes.
+      positionInShimFile -= 1;
+    }
+    const res: ShimLocation = {
+      shimPath: this.shimPath,
+      positionInShimFile,
+    };
+    this.expressionCompletionCache.set(expr, res);
+    return res;
+  }
+
   /**
    * Get global completions within the given template context - either a `TmplAstTemplate` embedded
    * view, or `null` for the root context.

packages/language-service/ivy/completions.ts

@@ -9,7 +9,7 @@
 import {AST, BindingPipe, EmptyExpr, ImplicitReceiver, LiteralPrimitive, MethodCall, ParseSourceSpan, PropertyRead, PropertyWrite, SafeMethodCall, SafePropertyRead, TmplAstBoundAttribute, TmplAstBoundEvent, TmplAstElement, TmplAstNode, TmplAstReference, TmplAstTemplate, TmplAstText, TmplAstTextAttribute, TmplAstVariable} from '@angular/compiler';
 import {NgCompiler} from '@angular/compiler-cli/src/ngtsc/core';
 import {CompletionKind, DirectiveInScope, TemplateDeclarationSymbol} from '@angular/compiler-cli/src/ngtsc/typecheck/api';
-import {BoundEvent} from '@angular/compiler/src/render3/r3_ast';
+import {BoundEvent, TextAttribute} from '@angular/compiler/src/render3/r3_ast';
 import * as ts from 'typescript';
 
 import {addAttributeCompletionEntries, AttributeCompletionKind, buildAttributeCompletionTable, getAttributeCompletionSymbol} from './attribute_completions';
@@ -26,6 +26,8 @@ type ElementAttributeCompletionBuilder =
 
 type PipeCompletionBuilder = CompletionBuilder<BindingPipe>;
 
+type LiteralCompletionBuilder = CompletionBuilder<LiteralPrimitive|TextAttribute>;
+
 export enum CompletionNodeContext {
   None,
   ElementTag,
@@ -72,11 +74,71 @@ export class CompletionBuilder<N extends TmplAstNode|AST> {
       return this.getElementAttributeCompletions();
     } else if (this.isPipeCompletion()) {
       return this.getPipeCompletions();
+    } else if (this.isLiteralCompletion()) {
+      return this.getLiteralCompletions(options);
     } else {
       return undefined;
     }
   }
 
+  private isLiteralCompletion(): this is LiteralCompletionBuilder {
+    return this.node instanceof LiteralPrimitive ||
+        (this.node instanceof TextAttribute &&
+         this.nodeContext === CompletionNodeContext.ElementAttributeValue);
+  }
+
+  private getLiteralCompletions(
+      this: LiteralCompletionBuilder, options: ts.GetCompletionsAtPositionOptions|undefined):
+      ts.WithMetadata<ts.CompletionInfo>|undefined {
+    const location = this.compiler.getTemplateTypeChecker().getLiteralCompletionLocation(
+        this.node, this.component);
+    if (location === null) {
+      return undefined;
+    }
+    const tsResults =
+        this.tsLS.getCompletionsAtPosition(location.shimPath, location.positionInShimFile, options);
+    if (tsResults === undefined) {
+      return undefined;
+    }
+
+    let replacementSpan: ts.TextSpan|undefined;
+    if (this.node instanceof TextAttribute && this.node.value.length > 0 && this.node.valueSpan) {
+      replacementSpan = {
+        start: this.node.valueSpan.start.offset,
+        length: this.node.value.length,
+      };
+    }
+    if (this.node instanceof LiteralPrimitive) {
+      if (typeof this.node.value === 'string' && this.node.value.length > 0) {
+        replacementSpan = {
+          // The sourceSpan of `LiteralPrimitive` includes the open quote and the completion entries
+          // don't, so skip the open quote here.
+          start: this.node.sourceSpan.start + 1,
+          length: this.node.value.length,
+        };
+      } else if (typeof this.node.value === 'number') {
+        replacementSpan = {
+          start: this.node.sourceSpan.start,
+          length: this.node.value.toString().length,
+        };
+      }
+    }
+
+    let ngResults: ts.CompletionEntry[] = [];
+    for (const result of tsResults.entries) {
+      if (this.isValidNodeContextCompletion(result)) {
+        ngResults.push({
+          ...result,
+          replacementSpan,
+        });
+      }
+    }
+    return {
+      ...tsResults,
+      entries: ngResults,
+    };
+  }
+
   /**
    * Analogue for `ts.LanguageService.getCompletionEntryDetails`.
    */
@@ -749,6 +811,8 @@ function nodeContextFromTarget(target: TargetContext): CompletionNodeContext {
     case TargetNodeKind.AttributeInValueContext:
       if (target.node instanceof TmplAstBoundEvent) {
         return CompletionNodeContext.EventValue;
+      } else if (target.node instanceof TextAttribute) {
+        return CompletionNodeContext.ElementAttributeValue;
       } else {
         return CompletionNodeContext.None;
       }

packages/language-service/ivy/test/completions_spec.ts

@@ -116,6 +116,19 @@ const SOME_PIPE = {
    `
 };
 
+const UNION_TYPE_PIPE = {
+  'UnionTypePipe': `
+    @Pipe({
+      name: 'unionTypePipe',
+    })
+    export class UnionTypePipe {
+      transform(value: string, config: 'foo' | 'bar'): string {
+        return value;
+      }
+    }
+   `
+};
+
 describe('completions', () => {
   beforeEach(() => {
     initMockFileSystem('Native');
@@ -749,6 +762,50 @@ describe('completions', () => {
       expect(completions?.entries.length).toBe(0);
     });
   });
+
+  describe('literal primitive scope', () => {
+    it('should complete a string union types in square brackets binding', () => {
+      const {templateFile} = setup(`<input dir [myInput]="'foo'">`, '', DIR_WITH_UNION_TYPE_INPUT);
+      templateFile.moveCursorToText(`[myInput]="'foo¦'"`);
+      const completions = templateFile.getCompletionsAtPosition();
+      expectContain(completions, ts.ScriptElementKind.string, ['foo']);
+      expectReplacementText(completions, templateFile.contents, 'foo');
+    });
+
+    it('should complete a string union types in binding without brackets', () => {
+      const {templateFile} = setup(`<input dir myInput="foo">`, '', DIR_WITH_UNION_TYPE_INPUT);
+      templateFile.moveCursorToText('myInput="foo¦"');
+      const completions = templateFile.getCompletionsAtPosition();
+      expectContain(completions, ts.ScriptElementKind.string, ['foo']);
+      expectReplacementText(completions, templateFile.contents, 'foo');
+    });
+
+    it('should complete a string union types in binding without brackets when the cursor at the start of the string',
+       () => {
+         const {templateFile} = setup(`<input dir myInput="foo">`, '', DIR_WITH_UNION_TYPE_INPUT);
+         templateFile.moveCursorToText('myInput="¦foo"');
+         const completions = templateFile.getCompletionsAtPosition();
+         expectContain(completions, ts.ScriptElementKind.string, ['foo']);
+         expectReplacementText(completions, templateFile.contents, 'foo');
+       });
+
+    it('should complete a string union types in pipe', () => {
+      const {templateFile} =
+          setup(`<input dir [myInput]="'foo'|unionTypePipe:'bar'">`, '', UNION_TYPE_PIPE);
+      templateFile.moveCursorToText(`[myInput]="'foo'|unionTypePipe:'bar¦'"`);
+      const completions = templateFile.getCompletionsAtPosition();
+      expectContain(completions, ts.ScriptElementKind.string, ['bar']);
+      expectReplacementText(completions, templateFile.contents, 'bar');
+    });
+
+    it('should complete a number union types', () => {
+      const {templateFile} = setup(`<input dir [myInput]="42">`, '', DIR_WITH_UNION_TYPE_INPUT);
+      templateFile.moveCursorToText(`[myInput]="42¦"`);
+      const completions = templateFile.getCompletionsAtPosition();
+      expectContain(completions, ts.ScriptElementKind.string, ['42']);
+      expectReplacementText(completions, templateFile.contents, '42');
+    });
+  });
 });
 
 function expectContain(