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Closure Compiler is a JavaScript optimizing compiler. It parses your JavaScript, analyzes it, removes dead code and rewrites and minimizes what's left. It also checks syntax, variable references, and types, and warns about common JavaScript pitfalls. It is used in many of Google's JavaScript apps, including Gmail, Google Web Search, Google Maps, and Google Docs. This binary checks for style issues such as incorrect or missing JSDoc usage, and missing goog.require() statements. It does not do more advanced checks such as typechecking.

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/*
 * Copyright 2014 The Closure Compiler Authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.google.javascript.jscomp.lint;

import com.google.javascript.jscomp.AbstractCompiler;
import com.google.javascript.jscomp.DiagnosticType;
import com.google.javascript.jscomp.HotSwapCompilerPass;
import com.google.javascript.jscomp.NodeTraversal;
import com.google.javascript.jscomp.NodeTraversal.AbstractPostOrderCallback;
import com.google.javascript.jscomp.NodeUtil;
import com.google.javascript.rhino.JSDocInfo;
import com.google.javascript.rhino.Node;

/**
 * Checks for errors related to interfaces.
 *
 */
public final class CheckInterfaces extends AbstractPostOrderCallback
    implements HotSwapCompilerPass {
  public static final DiagnosticType NON_DECLARATION_STATEMENT_IN_RECORD =
      DiagnosticType.disabled(
          "JSC_NON_DECLARATION_STATEMENT_IN_RECORD",
          "@record functions should not contain statements other than field declarations");

  public static final DiagnosticType INTERFACE_FUNCTION_NOT_EMPTY =
      DiagnosticType.disabled(
          "JSC_INTERFACE_FUNCTION_NOT_EMPTY",
          "interface functions must have an empty body");

  public static final DiagnosticType INTERFACE_SHOULD_NOT_TAKE_ARGS =
      DiagnosticType.disabled(
          "JSC_INTERFACE_SHOULD_NOT_TAKE_ARGS",
          "Interface functions should not take any arguments");

  private final AbstractCompiler compiler;

  public CheckInterfaces(AbstractCompiler compiler) {
    this.compiler = compiler;
  }

  @Override
  public void process(Node externs, Node root) {
    NodeTraversal.traverse(compiler, root, this);
  }

  @Override
  public void hotSwapScript(Node scriptRoot, Node originalRoot) {
    NodeTraversal.traverse(compiler, scriptRoot, this);
  }

  /** Whether a function is an interface constructor, or a method on an interface. */
  private boolean isInterface(Node n) {
    if (!n.isFunction()) {
      return false;
    }

    JSDocInfo jsDoc = NodeUtil.getBestJSDocInfo(n);
    return jsDoc != null && jsDoc.isInterface();
  }


  @Override
  public void visit(NodeTraversal t, Node n, Node parent) {
    if (!isInterface(n)) {
      return;
    }

    Node args = n.getSecondChild();
    if (args.hasChildren()) {
      t.report(args.getFirstChild(), INTERFACE_SHOULD_NOT_TAKE_ARGS);
    }

    Node block = n.getLastChild();
    if (block.hasChildren()) {
      if (NodeUtil.getBestJSDocInfo(n).usesImplicitMatch()) {
        for (Node stmt : block.children()) {
          if (stmt.isExprResult()
              && stmt.getFirstChild().isGetProp()
              && stmt.getFirstFirstChild().isThis()
              && stmt.getFirstChild().getJSDocInfo() != null) {
            // Field declarations are expected.
          } else {
            t.report(stmt, NON_DECLARATION_STATEMENT_IN_RECORD);
            return;
          }
        }
      } else {
        t.report(block.getFirstChild(), INTERFACE_FUNCTION_NOT_EMPTY);
      }
    }
  }
}