API, Build: Explicitly pass version into Git Properties Plugin

api/src/test/java/org/apache/iceberg/TestIcebergBuild.java

@@ -19,7 +19,11 @@
 package org.apache.iceberg;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assumptions.assumeThat;
 
+import java.io.IOException;
+import java.nio.file.Path;
+import java.nio.file.Paths;
 import java.util.Locale;
 import java.util.regex.Pattern;
 import org.junit.jupiter.api.Test;
@@ -37,6 +41,34 @@ public void testFullVersion() {
                 + ")");
   }
 
+  @Test
+  public void testVersionNotUnspecified() {
+    assertThat(IcebergBuild.version()).isNotEqualTo("unspecified");
+  }
+
+  @Test
+  public void testVersionMatchesSystemProperty() {
+    assumeThat(System.getProperty("project.version")).isNotNull();
+    assertThat(IcebergBuild.version())
+        .isEqualTo(System.getProperty("project.version"))
+        .as("IcebergBuild.version() should match system property project.version");
+  }
+
+  /**
+   * This test is for Source Releases. When we have a source release we use a version.txt file in
+   * the parent directory of this module to actually set the "version" which should be included in
+   * the gradle build properties used by IcebergBuild.
+   */
+  @Test
+  public void testVersionMatchesFile() throws IOException {
+    Path versionPath = Paths.get("../version.txt").toAbsolutePath();
+    assumeThat(java.nio.file.Files.exists(versionPath)).isTrue();
+    String versionText = java.nio.file.Files.readString(versionPath).trim();
+    assertThat(IcebergBuild.version())
+        .isEqualTo(versionText)
+        .as("IcebergBuild.version() should match version file");
+  }
+
   @Test
   public void testVersion() {
     assertThat(IcebergBuild.version()).as("Should not use unknown version").isNotEqualTo("unknown");

build.gradle

@@ -95,6 +95,7 @@ gitProperties {
   failOnNoGitDirectory = true
   keys = ['git.branch', 'git.build.version', 'git.closest.tag.name','git.commit.id.abbrev', 'git.commit.id',
           'git.commit.message.short', 'git.commit.time', 'git.tags']
+  version = projectVersion
 }
 generateGitProperties.outputs.upToDateWhen { false }
 
@@ -233,6 +234,8 @@ subprojects {
       events "failed"
       exceptionFormat "full"
     }
+
+    systemProperty 'project.version', project.version
   }
 
   plugins.withType(ScalaPlugin.class) {