fix(language-service): Improve signature selection for pipes with args

packages/compiler-cli/src/diagnostics/expression_diagnostics.ts

@@ -335,4 +335,4 @@ function offsetSpan(span: Span, amount: number): Span {
 
 function spanOf(sourceSpan: ParseSourceSpan): Span {
   return {start: sourceSpan.start.offset, end: sourceSpan.end.offset};
-}
+}

packages/compiler-cli/src/diagnostics/typescript_symbols.ts

@@ -557,7 +557,7 @@ class PipeSymbol implements Symbol {
 
   selectSignature(types: Symbol[]): Signature|undefined {
     let signature = selectSignature(this.tsType, this.context, types) !;
-    if (types.length == 1) {
+    if (types.length > 0) {
       const parameterType = types[0];
       if (parameterType instanceof TypeWrapper) {
         let resultType: ts.Type|undefined = undefined;
@@ -575,7 +575,7 @@ class PipeSymbol implements Symbol {
             }
             break;
           case 'slice':
-            resultType = getTypeParameterOf(parameterType.tsType, 'Array');
+            resultType = parameterType.tsType;
             break;
         }
         if (resultType) {

packages/language-service/test/diagnostics_spec.ts

@@ -76,6 +76,26 @@ describe('diagnostics', () => {
     }
   });
 
+  it('should not produce diagnostics for slice pipe with arguments', () => {
+    mockHost.override(TEST_TEMPLATE, `
+      <div *ngFor="let h of heroes | slice:0:1">
+        {{h.name}}
+      </div>`);
+    const diags = ngLS.getDiagnostics(TEST_TEMPLATE);
+    expect(diags).toEqual([]);
+  });
+
+  it('should produce diagnostics for slice pipe with args when member is invalid', () => {
+    mockHost.override(TEST_TEMPLATE, `
+      <div *ngFor="let h of heroes | slice:0:1">
+        {{h.age}}
+      </div>`);
+    const diags = ngLS.getDiagnostics(TEST_TEMPLATE);
+    expect(diags.length).toBe(1);
+    expect(diags[0].messageText)
+        .toBe(`Identifier 'age' is not defined. 'Hero' does not contain such a member`);
+  });
+
   describe('in expression-cases.ts', () => {
     it('should report access to an unknown field', () => {
       const diags = ngLS.getDiagnostics(EXPRESSION_CASES).map(d => d.messageText);

packages/language-service/test/project/app/parsing-cases.ts

@@ -188,6 +188,7 @@ export class TestComponent {
 export class TemplateReference {
   title = 'Some title';
   hero: Hero = {id: 1, name: 'Windstorm'};
+  heroes: Hero[] = [this.hero];
   anyValue: any;
   myClick(event: any) {}
 }