Move CompletionTarget and OpType for use by plugins

pkg/analysis_server/lib/src/provisional/completion/dart/completion_target.dart

Index: pkg/analysis_server/lib/src/provisional/completion/dart/completion_target.dart
diff --git a/pkg/analysis_server/lib/src/provisional/completion/dart/completion_target.dart b/pkg/analysis_server/lib/src/provisional/completion/dart/completion_target.dart
deleted file mode 100644
index 840dbaf99bdb0f70526c649f591ff1e36353a7aa..0000000000000000000000000000000000000000
--- a/pkg/analysis_server/lib/src/provisional/completion/dart/completion_target.dart
+++ /dev/null
@@ -1,455 +0,0 @@
-// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-import 'package:analyzer/dart/ast/ast.dart';
-import 'package:analyzer/dart/ast/token.dart';
-import 'package:analyzer/dart/element/element.dart';
-import 'package:analyzer/dart/element/type.dart';
-import 'package:analyzer/src/generated/utilities_dart.dart';
-
-int _computeArgIndex(AstNode containingNode, Object entity) {
-  var argList = containingNode;
-  if (argList is NamedExpression) {
-    entity = argList;
-    argList = argList.parent;
-  }
-  if (argList is ArgumentList) {
-    NodeList<Expression> args = argList.arguments;
-    for (int index = 0; index < args.length; ++index) {
-      if (entity == args[index]) {
-        return index;
-      }
-    }
-    if (args.isEmpty) {
-      return 0;
-    }
-    if (entity == argList.rightParenthesis) {
-      // Parser ignores trailing commas
-      if (argList.rightParenthesis.previous?.lexeme == ',') {
-        return args.length;
-      }
-      return args.length - 1;
-    }
-  }
-  return null;
-}
-
-/**
- * A CompletionTarget represents an edge in the parse tree which connects an
- * AST node (the [containingNode] of the completion) to one of its children
- * (the [entity], which represents the place in the parse tree where the newly
- * completed text will be inserted).
- *
- * To illustrate, consider the following snippet of code, and its associated
- * parse tree.  (T's represent tokens, N's represent AST nodes.  Some trivial
- * AST nodes are not shown).
- *
- *            ___N        (function declaration)
- *           /    \
- *          /    __N_______  (function body)
- *         /    /  |a      \
- *        /    /   N______  \  (statement)
- *       /    /   /       \  \
- *      /    /   N____     \  \  (assignment expression)
- *     |    /   /|    \     \  \
- *     .   |   / |    _N___  \  |  ("as" expression)
- *     .   |  |  |   / |   \c | |
- *     .   |  N  |  N  |b   N | |  (simple identifiers)
- *         |  |  |  |  |    | | |
- *         T  T  T  T  T    T T T
- *     m() { foo = bar as  Baz; }
- *
- * The Completion target is usually placed as high in the tree as possible so
- * that we can produce the most meaningful completions with minimal effort.
- * For instance, if the cursor is inside the identifier "foo", the completion
- * target will be the edge marked "a", so that we will produce all completions
- * that could possibly start a statement, even those which would conflict with
- * the current parse (such as the keyword "for", which begins a "for"
- * statement).  As a consequence of this, the [entity] will usually not be the
- * first child of the [containingNode] node.
- *
- * Note that the [containingNode] is always an AST node, but the [entity] may
- * not be.  For instance, if the cursor is inside the keyword "as", the
- * completion target will be the edge marked "b", so the [entity] is the token
- * "as".
- *
- * If the cursor is between tokens, the completion target is usually associated
- * with the token that follows the cursor (since that's the token that will be
- * displaced when the new text is inserted).  For example, if the cursor is
- * after the "{" character, then the completion target will be the edge marked
- * "a", just as it is if the cursor is inside the identifier "foo".  However
- * there is one exception: if the cursor is at the rightmost edge of a keyword
- * or identifier, then the completion target is associated with that token,
- * since any further letters typed will change the meaning of the identifier or
- * keyword, rather than creating a new token.  So for instance, if the cursor
- * is just after the "s" of "as", the completion target will be the edge marked
- * "b", but if the cursor target is after the first space following "as", then
- * the completion target will be the edge marked "c".
- *
- * If the file is empty, or the cursor is after all the text in the file, then
- * there may be no edge in the parse tree which is appropriate to act as the
- * completion target; in this case, [entity] is set to null and
- * [containingNode] is set to the CompilationUnit.
- *
- * Clients may not extend, implement or mix-in this class.
- */
-class CompletionTarget {
-  /**
-   * The compilation unit in which the completion is occurring.
-   */
-  final CompilationUnit unit;
-
-  /**
-   * The offset within the source at which the completion is being requested.
-   */
-  final int offset;
-
-  /**
-   * The context in which the completion is occurring.  This is the AST node
-   * which is a direct parent of [entity].
-   */
-  final AstNode containingNode;
-
-  /**
-   * The entity which the completed text will replace (or which will be
-   * displaced once the completed text is inserted).  This may be an AstNode or
-   * a Token, or it may be null if the cursor is after all tokens in the file.
-   *
-   * Usually, the entity won't be the first child of the [containingNode] (this
-   * is a consequence of placing the completion target as high in the tree as
-   * possible).  However, there is one exception: when the cursor is inside of
-   * a multi-character token which is not a keyword or identifier (e.g. a
-   * comment, or a token like "+=", the entity will be always be the token.
-   */
-  final Object entity;
-
-  /**
-   * The [entity] is a comment token, which is either not a documentation
-   * comment or the position is not in a [CommentReference].
-   */
-  final bool isCommentText;
-
-  /**
-   * If the target is an argument in an [ArgumentList], then this is the index
-   * of the argument in the list, otherwise this is `null`.
-   */
-  final int argIndex;
-
-  /**
-   * 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 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
-    // first edge which points to an entity satisfying either _isCandidateToken
-    // or _isCandidateNode is the completion target.  If no edge is found that
-    // satisfies these two predicates, then we set the completion target entity
-    // to null and the containingNode to the entryPoint.
-    //
-    // Note that if a token is not a candidate target, then none of the tokens
-    // that precede it are candidate targets either.  Therefore any entity
-    // whose last token is not a candidate target can be skipped.  This lets us
-    // 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;
-    AstNode containingNode = entryPoint;
-    outerLoop:
-    while (true) {
-      if (containingNode is Comment) {
-        // Comments are handled specially: we descend into any CommentReference
-        // child node that contains the cursor offset.
-        Comment comment = containingNode;
-        for (CommentReference commentReference in comment.references) {
-          if (commentReference.offset <= offset &&
-              offset <= commentReference.end) {
-            containingNode = commentReference;
-            continue outerLoop;
-          }
-        }
-      }
-      for (var entity in containingNode.childEntities) {
-        if (entity is Token) {
-          if (_isCandidateToken(entity, offset)) {
-            // Try to replace with a comment token.
-            Token commentToken = _getContainingCommentToken(entity, offset);
-            if (commentToken != null) {
-              return new CompletionTarget._(
-                  compilationUnit, offset, containingNode, commentToken, true);
-            }
-            // Target found.
-            return new CompletionTarget._(
-                compilationUnit, offset, containingNode, entity, false);
-          } else {
-            // Since entity is a token, we don't need to look inside it; just
-            // proceed to the next entity.
-            continue;
-          }
-        } else if (entity is AstNode) {
-          // If the last token in the node isn't a candidate target, then
-          // neither the node nor any of its descendants can possibly be the
-          // completion target, so we can skip the node entirely.
-          if (!_isCandidateToken(entity.endToken, offset)) {
-            continue;
-          }
-
-          // If the node is a candidate target, then we are done.
-          if (_isCandidateNode(entity, offset)) {
-            // Check to see if the offset is in a preceding comment
-            Token commentToken =
-                _getContainingCommentToken(entity.beginToken, offset);
-            if (commentToken != null) {
-              // If the preceding comment is dartdoc token, then update
-              // the containing node to be the dartdoc comment.
-              // Otherwise completion is not required.
-              Comment docComment =
-                  _getContainingDocComment(containingNode, commentToken);
-              if (docComment != null) {
-                return new CompletionTarget._(
-                    compilationUnit, offset, docComment, commentToken, false);
-              } else {
-                return new CompletionTarget._(compilationUnit, offset,
-                    compilationUnit, commentToken, true);
-              }
-            }
-            return new CompletionTarget._(
-                compilationUnit, offset, containingNode, entity, false);
-          }
-
-          // Otherwise, the completion target is somewhere inside the entity,
-          // so we need to jump to the start of the outer loop to examine its
-          // contents.
-          containingNode = entity;
-          continue outerLoop;
-        } else {
-          // Unexpected entity found (all entities in a parse tree should be
-          // AST nodes or tokens).
-          assert(false);
-        }
-      }
-
-      // No completion target found.  It should only be possible to reach here
-      // the first time through the outer loop (since we only jump to the start
-      // of the outer loop after determining that the completion target is
-      // inside an entity).  We can check that assumption by verifying that
-      // containingNode is still the entryPoint.
-      assert(identical(containingNode, entryPoint));
-
-      // Since no completion target was found, we set the completion target
-      // entity to null and use the entryPoint as the parent.
-      return new CompletionTarget._(
-          compilationUnit, offset, entryPoint, null, false);
-    }
-  }
-
-  /**
-   * Create a [CompletionTarget] holding the given [containingNode] and
-   * [entity].
-   */
-  CompletionTarget._(this.unit, this.offset, AstNode containingNode,
-      Object entity, this.isCommentText)
-      : this.containingNode = containingNode,
-        this.entity = entity,
-        this.argIndex = _computeArgIndex(containingNode, entity);
-
-  /**
-   * Return `true` if the [containingNode] is a cascade
-   * and the completion insertion is not between the two dots.
-   * For example, `..d^` and `..^d` are considered a cascade
-   * from a completion standpoint, but `.^.d` is not.
-   */
-  bool get isCascade {
-    AstNode node = containingNode;
-    if (node is PropertyAccess) {
-      return node.isCascaded && offset > node.operator.offset + 1;
-    }
-    if (node is MethodInvocation) {
-      return node.isCascaded && offset > node.operator.offset + 1;
-    }
-    return false;
-  }
-
-  /**
-   * Return `true` if the target is a functional argument in an argument list.
-   * The target [AstNode] hierarchy *must* be resolved for this to work.
-   * See [maybeFunctionalArgument].
-   */
-  bool isFunctionalArgument() {
-    if (!maybeFunctionalArgument()) {
-      return false;
-    }
-    AstNode parent = containingNode.parent;
-    if (parent is ArgumentList) {
-      parent = parent.parent;
-    }
-    if (parent is InstanceCreationExpression) {
-      DartType instType = parent.bestType;
-      if (instType != null) {
-        Element intTypeElem = instType.element;
-        if (intTypeElem is ClassElement) {
-          SimpleIdentifier constructorName = parent.constructorName.name;
-          ConstructorElement constructor = constructorName != null
-              ? intTypeElem.getNamedConstructor(constructorName.name)
-              : intTypeElem.unnamedConstructor;
-          return constructor != null &&
-              _isFunctionalParameter(
-                  constructor.parameters, argIndex, containingNode);
-        }
-      }
-    } else if (parent is MethodInvocation) {
-      SimpleIdentifier methodName = parent.methodName;
-      if (methodName != null) {
-        Element methodElem = methodName.bestElement;
-        if (methodElem is MethodElement) {
-          return _isFunctionalParameter(
-              methodElem.parameters, argIndex, containingNode);
-        } else if (methodElem is FunctionElement) {
-          return _isFunctionalParameter(
-              methodElem.parameters, argIndex, containingNode);
-        }
-      }
-    }
-    return false;
-  }
-
-  /**
-   * Return `true` if the target maybe a functional argument in an argument list.
-   * This is used in determining whether the target [AstNode] hierarchy
-   * needs to be resolved so that [isFunctionalArgument] will work.
-   */
-  bool maybeFunctionalArgument() {
-    if (argIndex != null) {
-      if (containingNode is ArgumentList) {
-        return true;
-      }
-      if (containingNode is NamedExpression) {
-        if (containingNode.parent is ArgumentList) {
-          return true;
-        }
-      }
-    }
-    return false;
-  }
-
-  /**
-   * Determine if the offset is contained in a preceding comment token
-   * and return that token, otherwise return `null`.
-   */
-  static Token _getContainingCommentToken(Token token, int offset) {
-    if (token == null) {
-      return null;
-    }
-    if (offset >= token.offset) {
-      return null;
-    }
-    token = token.precedingComments;
-    while (token != null) {
-      if (offset <= token.offset) {
-        return null;
-      }
-      if (offset <= token.end) {
-        if (token.type == TokenType.SINGLE_LINE_COMMENT || offset < token.end) {
-          return token;
-        }
-      }
-      token = token.next;
-    }
-    return null;
-  }
-
-  /**
-   * Determine if the given token is part of the given node's dart doc.
-   */
-  static Comment _getContainingDocComment(AstNode node, Token token) {
-    if (node is AnnotatedNode) {
-      Comment docComment = node.documentationComment;
-      if (docComment != null && docComment.tokens.contains(token)) {
-        return docComment;
-      }
-    }
-    return null;
-  }
-
-  /**
-   * Determine whether [node] could possibly be the [entity] for a
-   * [CompletionTarget] associated with the given [offset].
-   */
-  static bool _isCandidateNode(AstNode node, int offset) {
-    // If the node's first token is a keyword or identifier, then the node is a
-    // candidate entity if its first token is.
-    Token beginToken = node.beginToken;
-    if (beginToken.type.isKeyword || beginToken.type == TokenType.IDENTIFIER) {
-      return _isCandidateToken(beginToken, offset);
-    }
-
-    // Otherwise, the node is a candidate entity only if the offset is before
-    // the beginning of the node.  This ensures that completions within a token
-    // (e.g. inside a literal string or inside a comment) are evaluated within
-    // the context of the token itself.
-    return offset <= node.offset;
-  }
-
-  /**
-   * Determine whether [token] could possibly be the [entity] for a
-   * [CompletionTarget] associated with the given [offset].
-   */
-  static bool _isCandidateToken(Token token, int offset) {
-    // A token is considered a candidate entity if the cursor offset is (a)
-    // before the start of the token, (b) within the token, (c) at the end of
-    // the token and the token is a keyword or identifier, or (d) at the
-    // location of the token and the token is zero length.
-    if (offset < token.end) {
-      return true;
-    } else if (offset == token.end) {
-      return token.type.isKeyword ||
-          token.type == TokenType.IDENTIFIER ||
-          token.length == 0;
-    } else if (!token.isSynthetic) {
-      return false;
-    }
-    // If the current token is synthetic, then check the previous token
-    // because it may have been dropped from the parse tree
-    Token previous = token.previous;
-    if (offset < previous.end) {
-      return true;
-    } else if (offset == previous.end) {
-      return token.type.isKeyword || previous.type == TokenType.IDENTIFIER;
-    } else {
-      return false;
-    }
-  }
-
-  /**
-   * Return `true` if the parameter is a functional parameter.
-   */
-  static bool _isFunctionalParameter(List<ParameterElement> parameters,
-      int paramIndex, AstNode containingNode) {
-    DartType paramType;
-    if (paramIndex < parameters.length) {
-      ParameterElement param = parameters[paramIndex];
-      if (param.parameterKind == ParameterKind.NAMED) {
-        if (containingNode is NamedExpression) {
-          String name = containingNode.name?.label?.name;
-          param = parameters.firstWhere(
-              (ParameterElement param) =>
-                  param.parameterKind == ParameterKind.NAMED &&
-                  param.name == name,
-              orElse: () => null);
-          paramType = param?.type;
-        }
-      } else {
-        paramType = param.type;
-      }
-    }
-    return paramType is FunctionType || paramType is FunctionTypeAlias;
-  }
-}