1// Copyright 2017 The Bazel Authors. All rights reserved.
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//    http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14package com.google.devtools.common.options;
15
16import java.io.IOException;
17import java.nio.file.FileSystem;
18import java.nio.file.Path;
19import java.util.List;
20
21/**
22 * Defines an {@link ArgsPreProcessor} that will determine if the arguments list contains a "params"
23 * file that contains a list of options to be parsed.
24 *
25 * <p>Params files are used when the argument list of {@link Option} exceed the shells commandline
26 * length. A params file argument is defined as a path starting with @. It will also be the only
27 * entry in an argument list.
28 */
29public abstract class ParamsFilePreProcessor implements ArgsPreProcessor {
30
31  static final String ERROR_MESSAGE_FORMAT = "Error reading params file: %s %s";
32
33  static final String TOO_MANY_ARGS_ERROR_MESSAGE_FORMAT =
34      "A params file must be the only argument: %s";
35
36  static final String UNFINISHED_QUOTE_MESSAGE_FORMAT = "Unfinished quote %s at %s";
37
38  private final FileSystem fs;
39
40  ParamsFilePreProcessor(FileSystem fs) {
41    this.fs = fs;
42  }
43
44  /**
45   * Parses the param file path and replaces the arguments list with the contents if one exists.
46   *
47   * @param args A list of arguments that may contain @&lt;path&gt; to a params file.
48   * @return A list of arguments suitable for parsing.
49   * @throws OptionsParsingException if the path does not exist.
50   */
51  @Override
52  public List<String> preProcess(List<String> args) throws OptionsParsingException {
53    if (!args.isEmpty() && args.get(0).startsWith("@")) {
54      if (args.size() > 1) {
55        throw new OptionsParsingException(
56            String.format(TOO_MANY_ARGS_ERROR_MESSAGE_FORMAT, args), args.get(0));
57      }
58      Path path = fs.getPath(args.get(0).substring(1));
59      try {
60        return parse(path);
61      } catch (RuntimeException | IOException e) {
62        throw new OptionsParsingException(
63            String.format(ERROR_MESSAGE_FORMAT, path, e.getMessage()), args.get(0), e);
64      }
65    }
66    return args;
67  }
68
69  /**
70   * Parses the paramsFile and returns a list of argument tokens to be further processed by the
71   * {@link OptionsParser}.
72   *
73   * @param paramsFile The path of the params file to parse.
74   * @return a list of argument tokens.
75   * @throws IOException if there is an error reading paramsFile.
76   * @throws OptionsParsingException if there is an error reading paramsFile.
77   */
78  protected abstract List<String> parse(Path paramsFile)
79      throws IOException, OptionsParsingException;
80}
81