java/dagger/internal/codegen/base/DiagnosticFormatting.java

/*
 * Copyright (C) 2017 The Dagger 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 dagger.internal.codegen.base;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * Utility methods for formatting diagnostics to the {@link javax.annotation.processing.Messager}.
 */
public final class DiagnosticFormatting {

  /**
   * A regular expression to match a small list of specific packages deemed to be unhelpful to
   * display in fully qualified types in error messages.
   *
   * <p>Note: This should never be applied to messages themselves.
   */
  private static final Pattern COMMON_PACKAGE_PATTERN =
      Pattern.compile(
          "(?:^|[^.a-z_])" // What we want to match on but not capture.
              + "((?:" // Start a group with a non-capturing or part
              + "java[.]lang"
              + "|java[.]util"
              + "|javax[.]inject"
              + "|dagger"
              + "|dagger[.]multibindings"
              + "|com[.]google[.]common[.]base"
              + "|com[.]google[.]common[.]collect"
              + ")[.])" // Always end with a literal .
              + "[A-Z]"); // What we want to match on but not capture.

  /**
   * A method to strip out common packages and a few rare type prefixes from types' string
   * representation before being used in error messages.
   *
   * <p>This type assumes a String value that is a valid fully qualified (and possibly
   * parameterized) type, and should NOT be used with arbitrary text, especially prose error
   * messages.
   *
   * <p>TODO(user): Tighten these to take type representations (mirrors and elements) to avoid
   * accidental mis-use by running errors through this method.
   */
  public static String stripCommonTypePrefixes(String type) {
    // Do regex magic to remove common packages we care to shorten.
    Matcher matcher = COMMON_PACKAGE_PATTERN.matcher(type);
    StringBuilder result = new StringBuilder();
    int index = 0;
    while (matcher.find()) {
      result.append(type.subSequence(index, matcher.start(1)));
      index = matcher.end(1); // Skip the matched pattern content.
    }
    result.append(type.subSequence(index, type.length()));
    return result.toString();
  }

  private DiagnosticFormatting() {}
}