Support downloading pre-built SNAPSHOT artifacts for BWC tests

Add a -Dbwc.buildUnreleasedFromSource=false flag that downloads pre-built
SNAPSHOT artifacts from artifacts.opensearch.org for unreleased versions
instead of checking out git branches and compiling from source. The
default behavior (building from source) is unchanged.

Signed-off-by: Andrew Ross <andrross@amazon.com>

Author: andrross

buildSrc/src/main/java/org/opensearch/gradle/info/BuildParams.java

@@ -61,6 +61,7 @@ public class BuildParams {
     private static Boolean isInternal;
     private static Integer defaultParallel;
     private static Boolean isSnapshotBuild;
+    private static Boolean buildUnreleasedFromSource;
     private static BwcVersions bwcVersions;
 
     /**
@@ -147,6 +148,10 @@ public static boolean isSnapshotBuild() {
         return value(BuildParams.isSnapshotBuild);
     }
 
+    public static boolean buildUnreleasedFromSource() {
+        return buildUnreleasedFromSource == null || buildUnreleasedFromSource;
+    }
+
     private static <T> T value(T object) {
         if (object == null) {
             String callingMethod = Thread.currentThread().getStackTrace()[2].getMethodName();
@@ -256,6 +261,10 @@ public void setIsSnapshotBuild(final boolean isSnapshotBuild) {
             BuildParams.isSnapshotBuild = isSnapshotBuild;
         }
 
+        public void setBuildUnreleasedFromSource(final boolean buildUnreleasedFromSource) {
+            BuildParams.buildUnreleasedFromSource = buildUnreleasedFromSource;
+        }
+
         public void setBwcVersions(BwcVersions bwcVersions) {
             BuildParams.bwcVersions = requireNonNull(bwcVersions);
         }

buildSrc/src/main/java/org/opensearch/gradle/info/GlobalBuildInfoPlugin.java

@@ -133,6 +133,7 @@ public void apply(Project project) {
             params.setDefaultParallel(findDefaultParallel(project));
             params.setInFipsJvm(FipsBuildParams.isInFipsMode());
             params.setIsSnapshotBuild(Util.getBooleanProperty("build.snapshot", true));
+            params.setBuildUnreleasedFromSource(Util.getBooleanProperty("bwc.buildUnreleasedFromSource", true));
             if (isInternal) {
                 params.setBwcVersions(resolveBwcVersions(rootDir));
             }

buildSrc/src/main/java/org/opensearch/gradle/internal/InternalDistributionDownloadPlugin.java

@@ -100,6 +100,10 @@ private void registerInternalDistributionResolutions(NamedDomainObjectContainer<
         resolutions.register("bwc", distributionResolution -> distributionResolution.setResolver((project, distribution) -> {
             BwcVersions.UnreleasedVersionInfo unreleasedInfo = bwcVersions.unreleasedInfo(Version.fromString(distribution.getVersion()));
             if (unreleasedInfo != null) {
+                if (BuildParams.buildUnreleasedFromSource() == false) {
+                    // Download pre-built SNAPSHOT artifacts instead of building from source
+                    return DistributionDependency.of(snapshotDependencyNotation(distribution));
+                }
                 if (distribution.getBundledJdk() == JavaPackageType.NONE) {
                     throw new GradleException(
                         "Configuring a snapshot bwc distribution ('"
@@ -195,6 +199,40 @@ private static String distributionProjectName(OpenSearchDistribution distributio
         return projectName;
     }
 
+    /**
+     * Constructs a dependency notation that resolves an unreleased version from the snapshot artifact repository.
+     */
+    private static String snapshotDependencyNotation(OpenSearchDistribution distribution) {
+        String snapshotVersion = distribution.getVersion() + "-SNAPSHOT";
+        String extension = distribution.getType().toString();
+        String classifier = ":x64";
+        if (distribution.getType() == OpenSearchDistribution.Type.ARCHIVE) {
+            extension = distribution.getPlatform() == OpenSearchDistribution.Platform.WINDOWS ? "zip" : "tar.gz";
+            switch (distribution.getArchitecture()) {
+                case ARM64:
+                    classifier = ":" + distribution.getPlatform() + "-arm64";
+                    break;
+                case X64:
+                    classifier = ":" + distribution.getPlatform() + "-x64";
+                    break;
+                case S390X:
+                    classifier = ":" + distribution.getPlatform() + "-s390x";
+                    break;
+                case PPC64LE:
+                    classifier = ":" + distribution.getPlatform() + "-ppc64le";
+                    break;
+                case RISCV64:
+                    classifier = ":" + distribution.getPlatform() + "-riscv64";
+                    break;
+                default:
+                    throw new IllegalArgumentException("Unsupported architecture: " + distribution.getArchitecture());
+            }
+        } else if (distribution.getType() == OpenSearchDistribution.Type.DEB) {
+            classifier = ":amd64";
+        }
+        return "opensearch-distribution-snapshot:opensearch:" + snapshotVersion + classifier + "@" + extension;
+    }
+
     private static class ProjectBasedDistributionDependency implements DistributionDependency {
 
         private Function<String, Dependency> function;