refactor(language-service): Append missing AttrAst to AstPath (#34459)

When a HTML Ast containing an Attribute node is converted to a Template Ast,
the attribute node might get dropped from the Template Ast path.
This is because the AttrNode is not even in the Template Ast to begin with.
In this case, we manually fix the path by converting the Attribute node
to a AttrAst node and appending it to the path.

This allows the `ExpressionVisitor` to properly visit the leaf node in the
TemplateAst path. We no longer need to visit the `Element` and look for
attributes.

PR Close #34459

packages/language-service/src/completions.ts

@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {AST, AstPath, Attribute, BoundDirectivePropertyAst, BoundElementPropertyAst, BoundEventAst, BoundTextAst, Element, ElementAst, ImplicitReceiver, NAMED_ENTITIES, Node as HtmlAst, NullTemplateVisitor, ParseSpan, PropertyRead, TagContentType, TemplateBinding, Text, getHtmlTagDefinition} from '@angular/compiler';
+import {AST, AstPath, AttrAst, Attribute, BoundDirectivePropertyAst, BoundElementPropertyAst, BoundEventAst, BoundTextAst, Element, ElementAst, ImplicitReceiver, NAMED_ENTITIES, Node as HtmlAst, NullTemplateVisitor, ParseSpan, PropertyRead, TagContentType, TemplateBinding, Text, getHtmlTagDefinition} from '@angular/compiler';
 import {$$, $_, isAsciiLetter, isDigit} from '@angular/compiler/src/chars';
 
 import {AstResult} from './common';
@@ -299,9 +299,16 @@ function attributeValueCompletions(
   if (!path.tail) {
     return [];
   }
+  // HtmlAst contains the `Attribute` node, however the corresponding `AttrAst`
+  // node is missing from the TemplateAst. In this case, we have to manually
+  // append the `AttrAst` node to the path.
+  if (!(path.tail instanceof AttrAst)) {
+    // The sourceSpan of an AttrAst is the valueSpan of the HTML Attribute.
+    path.push(new AttrAst(attr.name, attr.value, attr.valueSpan !));
+  }
   const dinfo = diagnosticInfoFromTemplateInfo(info);
   const visitor =
-      new ExpressionVisitor(info, position, () => getExpressionScope(dinfo, path, false), attr);
+      new ExpressionVisitor(info, position, () => getExpressionScope(dinfo, path, false));
   path.tail.visit(visitor, null);
   return visitor.results;
 }
@@ -391,8 +398,7 @@ class ExpressionVisitor extends NullTemplateVisitor {
 
   constructor(
       private readonly info: AstResult, private readonly position: number,
-      private readonly getExpressionScope: () => ng.SymbolTable,
-      private readonly attr?: Attribute) {
+      private readonly getExpressionScope: () => ng.SymbolTable) {
     super();
   }
 
@@ -409,18 +415,17 @@ class ExpressionVisitor extends NullTemplateVisitor {
   visitEvent(ast: BoundEventAst): void { this.addAttributeValuesToCompletions(ast.handler); }
 
   visitElement(ast: ElementAst): void {
-    if (!this.attr || !this.attr.valueSpan) {
-      return;
+    // no-op for now
   }
 
+  visitAttr(ast: AttrAst) {
     // The attribute value is a template expression but the expression AST
     // was not produced when the TemplateAst was produced so do that here.
     const {templateBindings} = this.info.expressionParser.parseTemplateBindings(
-        this.attr.name, this.attr.value, this.attr.sourceSpan.toString(),
-        this.attr.sourceSpan.start.offset);
+        ast.name, ast.value, ast.sourceSpan.toString(), ast.sourceSpan.start.offset);
 
     // Find where the cursor is relative to the start of the attribute value.
-    const valueRelativePosition = this.position - this.attr.valueSpan.start.offset;
+    const valueRelativePosition = this.position - ast.sourceSpan.start.offset;
     // Find the template binding that contains the position
     const binding = templateBindings.find(b => inSpan(valueRelativePosition, b.span));
 
@@ -428,16 +433,16 @@ class ExpressionVisitor extends NullTemplateVisitor {
       return;
     }
 
-    if (this.attr.name.startsWith('*')) {
-      this.microSyntaxInAttributeValue(this.attr, binding);
-    } else if (valueRelativePosition >= 0) {
+    if (ast.name.startsWith('*')) {
+      this.microSyntaxInAttributeValue(ast, binding);
+    } else {
       // If the position is in the expression or after the key or there is no key,
       // return the expression completions
-      const span = new ParseSpan(0, this.attr.value.length);
+      const span = new ParseSpan(0, ast.value.length);
       const offset = ast.sourceSpan.start.offset;
       const receiver = new ImplicitReceiver(span, span.toAbsolute(offset));
       const expressionAst = new PropertyRead(span, span.toAbsolute(offset), receiver, '');
-      this.addAttributeValuesToCompletions(expressionAst, valueRelativePosition);
+      this.addAttributeValuesToCompletions(expressionAst);
     }
   }
 
@@ -451,10 +456,9 @@ class ExpressionVisitor extends NullTemplateVisitor {
     }
   }
 
-  private addAttributeValuesToCompletions(value: AST, position?: number) {
+  private addAttributeValuesToCompletions(value: AST) {
     const symbols = getExpressionCompletions(
-        this.getExpressionScope(), value,
-        position === undefined ? this.attributeValuePosition : position, this.info.template.query);
+        this.getExpressionScope(), value, this.position, this.info.template.query);
     if (symbols) {
       this.addSymbolsToCompletions(symbols);
     }
@@ -474,13 +478,6 @@ class ExpressionVisitor extends NullTemplateVisitor {
     }
   }
 
-  private get attributeValuePosition() {
-    if (this.attr && this.attr.valueSpan) {
-      return this.position;
-    }
-    return 0;
-  }
-
   /**
    * This method handles the completions of attribute values for directives that
    * support the microsyntax format. Examples are *ngFor and *ngIf.
@@ -492,7 +489,7 @@ class ExpressionVisitor extends NullTemplateVisitor {
    * @param attr descriptor for attribute name and value pair
    * @param binding template binding for the expression in the attribute
    */
-  private microSyntaxInAttributeValue(attr: Attribute, binding: TemplateBinding) {
+  private microSyntaxInAttributeValue(attr: AttrAst, binding: TemplateBinding) {
     const key = attr.name.substring(1);  // remove leading asterisk
 
     // Find the selector - eg ngFor, ngIf, etc
@@ -510,7 +507,7 @@ class ExpressionVisitor extends NullTemplateVisitor {
       return;
     }
 
-    const valueRelativePosition = this.position - attr.valueSpan !.start.offset;
+    const valueRelativePosition = this.position - attr.sourceSpan.start.offset;
 
     if (binding.keyIsVar) {
       const equalLocation = attr.value.indexOf('=');
@@ -531,7 +528,7 @@ class ExpressionVisitor extends NullTemplateVisitor {
     }
 
     if (binding.expression && inSpan(valueRelativePosition, binding.expression.ast.span)) {
-      this.addAttributeValuesToCompletions(binding.expression.ast, this.position);
+      this.addAttributeValuesToCompletions(binding.expression.ast);
       return;
     }
   }