Method makeMessage

core/src/main/java/com/google/common/truth/Fact.java:190–255

Formats the given messages and facts into a string for use as the message of a test failure. In particular, this method horizontally aligns the beginning of fact values.

(List<String> messages, List<Fact> facts)

   * particular, this method horizontally aligns the beginning of fact values.
   */
  static String makeMessage(List<String> messages, List<Fact> facts) {
    int longestKeyLength = 0;
    int longestIntPartValueLength = 0;
    boolean seenNewlineInValue = false;
    for (Fact fact : facts) {
      if (fact.value != null) {
        longestKeyLength = max(longestKeyLength, fact.key.length());
        if (fact.padStart) {
          int decimalIndex = fact.value.indexOf('.');
          if (decimalIndex != -1) {
            longestIntPartValueLength = max(longestIntPartValueLength, decimalIndex);
          } else {
            longestIntPartValueLength = max(longestIntPartValueLength, fact.value.length());
          }
        }
        // TODO(cpovirk): Look for other kinds of newlines.
        seenNewlineInValue |= fact.value.contains("\n");
      }
    }

    StringBuilder builder = new StringBuilder();
    for (String message : messages) {
      builder.append(message);
      builder.append('\n');
    }

    /*
     * *Usually* the first fact is printed at the beginning of a new line. However, when this
     * exception is the cause of another exception, that exception will print it starting after
     * "Caused by: " on the same line. The other exception sometimes also reuses this message as its
     * own message. In both of those scenarios, the first line doesn't start at column 0, so the
     * horizontal alignment is thrown off.
     *
     * There's not much we can do about this, short of always starting with a newline (which would
     * leave a blank line at the beginning of the message in the normal case).
     */
    for (Fact fact : facts) {
      if (fact.value == null) {
        builder.append(fact.key);
      } else if (seenNewlineInValue) {
        builder.append(fact.key);
        builder.append(":\n");
        builder.append(indent(fact.value));
      } else {
        builder.append(padEnd(fact.key, longestKeyLength, ' '));
        builder.append(": ");
        if (fact.padStart) {
          int decimalIndex = fact.value.indexOf('.');
          if (decimalIndex != -1) {
            builder.append(
                padStart(fact.value.substring(0, decimalIndex), longestIntPartValueLength, ' '));
            builder.append(fact.value.substring(decimalIndex));
          } else {
            builder.append(padStart(fact.value, longestIntPartValueLength, ' '));
          }
        } else {
          builder.append(fact.value);
        }