#674: change timeformat from RFC822 to ISO 8601 to support maven's reproducible build feature

pom.xml

@@ -397,7 +397,7 @@
                             <dotGitDirectory>${project.basedir}/.git</dotGitDirectory>
                             <generateGitPropertiesFile>true</generateGitPropertiesFile>
                             <generateGitPropertiesFilename>target/testing.properties</generateGitPropertiesFilename>
-                            <dateFormat>yyyy-MM-dd'T'HH:mm:ssZ</dateFormat>
+                            <!-- <dateFormat>yyyy-MM-dd'T'HH:mm:ssXXX</dateFormat> -->
                             <dateFormatTimeZone>GMT-08:00</dateFormatTimeZone>
                             <useNativeGit>false</useNativeGit>
                             <abbrevLength>7</abbrevLength>

src/main/java/pl/project13/maven/git/GitCommitIdMojo.java

@@ -18,12 +18,12 @@
 
 package pl.project13.maven.git;
 
+import com.google.common.annotations.VisibleForTesting;
 import java.io.File;
 import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
-import java.text.DateFormat;
-import java.text.ParseException;
 import java.text.SimpleDateFormat;
+import java.time.Instant;
 import java.util.Collections;
 import java.util.Date;
 import java.util.List;
@@ -44,6 +44,7 @@
 import org.apache.maven.plugins.annotations.Parameter;
 import org.apache.maven.project.MavenProject;
 import org.apache.maven.settings.Settings;
+import org.joda.time.DateTime;
 import org.sonatype.plexus.build.incremental.BuildContext;
 import pl.project13.core.CommitIdGenerationMode;
 import pl.project13.core.CommitIdPropertiesOutputFormat;
@@ -497,20 +498,28 @@ public class GitCommitIdMojo extends AbstractMojo {
    * represents dates or times exported by this plugin (e.g. {@code git.commit.time}, {@code
    * git.build.time}). It should be a valid {@link SimpleDateFormat} string.
    *
-   * <p>The current dateFormat is set to match maven's default {@code yyyy-MM-dd'T'HH:mm:ssZ}.
-   * Please note that in previous versions (2.2.0 - 2.2.2) the default dateFormat was set to: {@code
-   * dd.MM.yyyy '@' HH:mm:ss z}. However the {@code RFC 822 time zone} seems to give a more reliable
-   * option in parsing the date and it's being used in maven as default.
+   * <p>The current dateFormat will be formatted as ISO 8601
+   * {@code yyyy-MM-dd'T'HH:mm:ssXXX} and therefore can be used as input to maven's
+   * <a href="https://maven.apache.org/guides/mini/guide-reproducible-builds.html">
+   * reproducible build</a> feature.
+   *
+   * Please note that in previous versions
+   * (2.2.2 - 7.0.1) the default format was set to {@code yyyy-MM-dd'T'HH:mm:ssZ}
+   * which produces a {@code RFC 822 time zone}. While such format gives reliable
+   * options in parsing the date, it does not comply with the requirements of
+   * the reproducible build feature.
+   * (2.2.0 - 2.2.2) the default dateFormat was set to: {@code
+   * dd.MM.yyyy '@' HH:mm:ss z}.
    *
    * <p>Example:
    *
    * <pre>{@code
-   * <dateFormat>yyyy-MM-dd'T'HH:mm:ssZ</dateFormat>
+   * <dateFormat>yyyy-MM-dd'T'HH:mm:ssXXX</dateFormat>
    * }</pre>
    *
    * @since 2.2.0
    */
-  @Parameter(defaultValue = "yyyy-MM-dd'T'HH:mm:ssZ")
+  @Parameter(defaultValue = "yyyy-MM-dd'T'HH:mm:ssXXX")
   String dateFormat;
 
   /**
@@ -1442,32 +1451,26 @@ private Properties getContextProperties(MavenProject project) {
    * href="https://reproducible-builds.org/docs/source-date-epoch/">SOURCE_DATE_EPOCH</a>.
    *
    * <p>Inspired by
-   * https://github.com/apache/maven-archiver/blob/a3103d99396cd8d3440b907ef932a33563225265/src/main/java/org/apache/maven/archiver/MavenArchiver.java#L765
+   * https://github.com/apache/maven-archiver/blob/7acb1db4a9754beacde3f21a69e5523ee901abd5/src/main/java/org/apache/maven/archiver/MavenArchiver.java#L755
    *
    * @param outputTimestamp the value of <code>${project.build.outputTimestamp}</code> (may be
    *     <code>null</code>)
    * @return the parsed timestamp, may be <code>null</code> if <code>null</code> input or input
    *     contains only 1 character
    */
-  private Date parseOutputTimestamp(String outputTimestamp) throws GitCommitIdExecutionException {
+  @VisibleForTesting
+  protected static Date parseOutputTimestamp(String outputTimestamp) {
     if (outputTimestamp != null
         && !outputTimestamp.trim().isEmpty()
         && outputTimestamp.chars().allMatch(Character::isDigit)) {
-      return new Date(Long.parseLong(outputTimestamp) * 1000);
+      return Date.from(Instant.ofEpochSecond(Long.parseLong(outputTimestamp)));
     }
 
     if ((outputTimestamp == null) || (outputTimestamp.length() < 2)) {
       // no timestamp configured
       return null;
     }
-
-    DateFormat df = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssXXX");
-    try {
-      return df.parse(outputTimestamp);
-    } catch (ParseException pe) {
-      throw new GitCommitIdExecutionException(
-          "Invalid 'project.build.outputTimestamp' value '" + outputTimestamp + "'", pe);
-    }
+    return new DateTime(outputTimestamp).toDate();
   }
 
   private void publishPropertiesInto(Properties propertiesToPublish, Properties propertiesTarget) {

src/test/java/pl/project13/maven/git/GitCommitIdMojoTest.java

@@ -22,12 +22,18 @@
 
 import java.io.File;
 import java.io.IOException;
+import java.time.Instant;
+import java.util.Date;
+import junitparams.JUnitParamsRunner;
+import junitparams.Parameters;
 import org.junit.Test;
+import org.junit.runner.RunWith;
 import pl.project13.core.PropertiesFileGenerator;
 
 /**
  * Testcases to verify that the git-commit-id works properly.
  */
+@RunWith(JUnitParamsRunner.class)
 public class GitCommitIdMojoTest {
   @Test
   public void testCraftPropertiesOutputFileWithRelativePath() throws IOException {
@@ -66,4 +72,137 @@ public void testCraftPropertiesOutputFileWithFullPath() throws IOException {
                 .toFile()
                 .getCanonicalPath());
   }
+
+  private Object[] parametersParseOutputTimestamp() {
+    return new Object[] {
+      // long since epoch
+      new Object[] {
+        "1644689403",
+        Instant.ofEpochMilli(1644689403000L)
+      },
+      // Date only:
+      new Object[] {
+        "2022-02",
+        Instant.ofEpochMilli(1643670000000L)
+      },
+      new Object[] {
+        "2022-02-12",
+        Instant.ofEpochMilli(1644620400000L)
+      },
+      // Date and time:
+      new Object[] {
+        "2022-02-12T15:30",
+        Instant.ofEpochMilli(1644676200000L)
+      },
+      new Object[] {
+        "2022-02-12T15:30:45",
+        Instant.ofEpochMilli(1644676245000L)
+      },
+      // Date and time with timezone:
+      new Object[] {
+        "2022-02-12T15:30+00:00",
+        Instant.ofEpochMilli(1644679800000L)
+      },
+      new Object[] {
+        "2022-02-12T15:30:45-05:00",
+        Instant.ofEpochMilli(1644697845000L)
+      },
+      new Object[] {
+        "2022-02-12T15:30:00+00:00",
+        Instant.ofEpochMilli(1644679800000L)
+      },
+      new Object[] {
+        "2023-11-30T09:17:06+05:30",
+        Instant.ofEpochMilli(1701316026000L)
+      },
+      new Object[] {
+        "2024-08-15T20:45:30-03:00",
+        Instant.ofEpochMilli(1723765530000L)
+      },
+      new Object[] {
+        "2022-02-12T15:30:00Z",
+        Instant.ofEpochMilli(1644679800000L)
+      },
+      // Not valid according to the ISO 8601 standard. The issue is with the time zone
+      // representation. ISO 8601 uses a specific format for time zones, either as "Z" for UTC or
+      // in the format "+HH:MM" or "-HH:MM" for the offset from UTC.
+      // The time zone "EST" or "PST" does not follow this format.
+      // new Object[] { "2023-11-30T09:17:06PST", null },
+      // new Object[] { "2024-08-15T20:45:30EST", null },
+      new Object[] {
+        "2023-11-30T09:17:06+0100",
+        Instant.ofEpochMilli(1701332226000L)
+      },
+      // Week date:
+      new Object[] {
+        "2022-W06",
+        Instant.ofEpochMilli(1644188400000L)
+      },
+      new Object[] {
+        "2022-W06-5",
+        Instant.ofEpochMilli(1644534000000L)
+      },
+      // Week date with time:
+      new Object[] {
+        "2022-W06-5T15:30",
+        Instant.ofEpochMilli(1644589800000L)
+      },
+      new Object[] {
+        "2022-W06-5T15:30:45",
+        Instant.ofEpochMilli(1644589845000L)
+      },
+      // https://tc39.es/proposal-uniform-interchange-date-parsing/cases.html
+      // positive leap second
+      // not working: new Object[] { "1972-06-30T23:59:60Z", null },
+      // Too few fractional second digits
+      new Object[] {
+        "2019-03-26T14:00:00.9Z",
+        Instant.ofEpochMilli(1553608800900L)
+      },
+      // Too many fractional second digits
+      new Object[] {
+        "2019-03-26T14:00:00.4999Z",
+        Instant.ofEpochMilli(1553608800499L)
+      },
+      // Too many fractional second digits (pre-epoch)
+      new Object[] {
+        "1969-03-26T14:00:00.4999Z",
+        Instant.ofEpochMilli(-24227999501L)
+      },
+      // Too many fractional second digits (BCE)
+      new Object[] {
+        "-000043-03-15T14:00:00.4999Z",
+        Instant.ofEpochMilli(-63517773599501L)
+      },
+      // Lowercase time designator
+      new Object[] {
+        "2019-03-26t14:00Z",
+        Instant.ofEpochMilli(1553608800000L)
+      },
+      // Lowercase UTC designator
+      new Object[] {
+        "2019-03-26T14:00z",
+        Instant.ofEpochMilli(1553608800000L)
+      },
+      // Hours-only offset
+      new Object[] {
+        "2019-03-26T10:00-04",
+        Instant.ofEpochMilli(1553608800000L)
+      },
+      // Fractional minutes
+      new Object[] {
+        "2019-03-26T14:00.9Z",
+        Instant.ofEpochMilli(1553608854000L)
+      },
+      // ISO basic format date and time
+      // not working: new Object[] { "20190326T1400Z", null },
+    };
+  }
+
+  @Test
+  @Parameters(method = "parametersParseOutputTimestamp")
+  public void testParseOutputTimestamp(String input, Instant expected) {
+    Date actual = GitCommitIdMojo.parseOutputTimestamp(input);
+    assertThat(actual.toInstant()).isEqualTo(expected);
+  }
 }

src/test/java/pl/project13/maven/git/NativeAndJGitProviderTest.java

@@ -56,8 +56,8 @@ public class NativeAndJGitProviderTest extends GitIntegrationTest {
         "git.local.branch.behind",
       };
 
-  private static final String DEFAULT_FORMAT_STRING = "yyyy-MM-dd'T'HH:mm:ssZ";
-  private static final String ISO8601_FORMAT_STRING = "yyyy-MM-dd'T'HH:mm:ssZZ";
+  private static final String DEFAULT_FORMAT_STRING = "yyyy-MM-dd'T'HH:mm:ssXXX";
+  private static final String ISO8601_FORMAT_STRING = "yyyy-MM-dd'T'HH:mm:ssXXX";
 
   @Test
   public void testCompareBasic() throws Exception {