From 1de757993da8160a2c41887470a6f70bd8554e82 Mon Sep 17 00:00:00 2001
From: Keen Yee Liau <kyliau@google.com>
Date: Thu, 24 Oct 2019 10:17:25 -0700
Subject: [PATCH] fix(language-service): Improve signature selection for pipes
 with args (#33456)

Pipes with arguments like `slice:0` or `slice:0:1` should not produce
diagnostic errors.

PR closes https://github.com/angular/vscode-ng-language-service/issues/345

PR Close #33456
---
 .../src/diagnostics/expression_diagnostics.ts |  2 +-
 .../src/diagnostics/typescript_symbols.ts     |  4 ++--
 .../language-service/test/diagnostics_spec.ts | 20 +++++++++++++++++++
 .../test/project/app/parsing-cases.ts         |  1 +
 4 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/packages/compiler-cli/src/diagnostics/expression_diagnostics.ts b/packages/compiler-cli/src/diagnostics/expression_diagnostics.ts
index 2253d2c077..135be11753 100644
--- a/packages/compiler-cli/src/diagnostics/expression_diagnostics.ts
+++ b/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};
-}
\ No newline at end of file
+}
diff --git a/packages/compiler-cli/src/diagnostics/typescript_symbols.ts b/packages/compiler-cli/src/diagnostics/typescript_symbols.ts
index 6f2d072866..99c63d9155 100644
--- a/packages/compiler-cli/src/diagnostics/typescript_symbols.ts
+++ b/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) {
diff --git a/packages/language-service/test/diagnostics_spec.ts b/packages/language-service/test/diagnostics_spec.ts
index 8672897401..daaa615435 100644
--- a/packages/language-service/test/diagnostics_spec.ts
+++ b/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);
diff --git a/packages/language-service/test/project/app/parsing-cases.ts b/packages/language-service/test/project/app/parsing-cases.ts
index a67b216bf0..8418fea484 100644
--- a/packages/language-service/test/project/app/parsing-cases.ts
+++ b/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) {}
 }