Create CompletionTarget with AstNode entry point.

When we resolve a file partially, there is no fully resolved
CompilationUnit. So, anything we create for completion should be
based on element models and a resolved, or unresolved AstNode.

In a following CL I will make it possible to create instances of
DartCompletionRequest based on such element models and node.

Change-Id: Ief7e376588bb63f4d898e33299a9fd2014c88843
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/219748
Commit-Queue: Konstantin Shcheglov <[email protected]>
Reviewed-by: Brian Wilkerson <[email protected]>

Author: scheglov

pkg/analyzer_plugin/lib/src/utilities/completion/completion_target.dart

@@ -119,14 +119,8 @@ class CompletionTarget {
   ParameterElement? _parameterElement;
 
   /// Compute the appropriate [CompletionTarget] for the given [offset] within
-  /// the [compilationUnit].
-  ///
-  /// Optionally, start the search from within [entryPoint] instead of using
-  /// the [compilationUnit], which is useful for analyzing ASTs that have no
-  /// [compilationUnit] such as dart expressions within angular templates.
-  factory CompletionTarget.forOffset(
-      CompilationUnit compilationUnit, int offset,
-      {AstNode? entryPoint}) {
+  /// the [entryPoint].
+  factory CompletionTarget.forOffset(AstNode entryPoint, int offset) {
     // The precise algorithm is as follows. We perform a depth-first search of
     // all edges in the parse tree (both those that point to AST nodes and
     // those that point to tokens), visiting parents before children. The
@@ -141,7 +135,6 @@ class CompletionTarget {
     // prune the search to the point where no recursion is necessary; at each
     // step in the process we know exactly which child node we need to proceed
     // to.
-    entryPoint ??= compilationUnit;
     var containingNode = entryPoint;
     outerLoop:
     while (true) {
@@ -197,7 +190,7 @@ class CompletionTarget {
                     offset, docComment, commentToken, false);
               } else {
                 return CompletionTarget._(
-                    offset, compilationUnit, commentToken, true);
+                    offset, entryPoint, commentToken, true);
               }
             }
             return CompletionTarget._(offset, containingNode, entity, false);
@@ -223,10 +216,12 @@ class CompletionTarget {
       assert(identical(containingNode, entryPoint));
 
       // Check for comments on the EOF token (trailing comments in a file).
-      var commentToken =
-          _getContainingCommentToken(compilationUnit.endToken, offset);
-      if (commentToken != null) {
-        return CompletionTarget._(offset, compilationUnit, commentToken, true);
+      if (entryPoint is CompilationUnit) {
+        var commentToken =
+            _getContainingCommentToken(entryPoint.endToken, offset);
+        if (commentToken != null) {
+          return CompletionTarget._(offset, entryPoint, commentToken, true);
+        }
       }
 
       // Since no completion target was found, we set the completion target

pkg/analyzer_plugin/lib/utilities/completion/inherited_reference_contributor.dart

@@ -59,8 +59,8 @@ class InheritedReferenceContributor
     CompletionTarget? target,
     OpType? optype,
   }) async {
-    target ??= CompletionTarget.forOffset(request.result.unit, request.offset,
-        entryPoint: entryPoint);
+    entryPoint ??= request.result.unit;
+    target ??= CompletionTarget.forOffset(entryPoint, request.offset);
     optype ??= OpType.forCompletion(target, request.offset);
     if (!optype.includeIdentifiers) {
       return;

pkg/analyzer_plugin/lib/utilities/completion/type_member_contributor.dart

@@ -29,7 +29,7 @@ class TypeMemberContributor implements CompletionContributor {
     var containingLibrary = request.result.libraryElement;
 
     // Recompute the target since resolution may have changed it
-    var expression = _computeDotTarget(request, null);
+    var expression = _computeDotTarget(request.result.unit, request.offset);
     if (expression == null || expression.isSynthetic) {
       return;
     }
@@ -42,18 +42,16 @@ class TypeMemberContributor implements CompletionContributor {
     var containingLibrary = request.result.libraryElement;
 
     // Recompute the target since resolution may have changed it
-    var expression = _computeDotTarget(request, entryPoint);
+    var expression = _computeDotTarget(entryPoint, request.offset);
     if (expression == null || expression.isSynthetic) {
       return;
     }
     _computeSuggestions(request, collector, containingLibrary, expression);
   }
 
   /// Update the completion [target] and [dotTarget] based on the given [unit].
-  Expression? _computeDotTarget(
-      DartCompletionRequest request, AstNode? entryPoint) {
-    var target = CompletionTarget.forOffset(request.result.unit, request.offset,
-        entryPoint: entryPoint);
+  Expression? _computeDotTarget(AstNode entryPoint, int offset) {
+    var target = CompletionTarget.forOffset(entryPoint, offset);
     return target.dotTarget;
   }