Allow pom download failures

rewrite-maven/build.gradle.kts

@@ -42,6 +42,7 @@ dependencies {
     testImplementation("com.squareup.okio:okio-jvm:3.9.1")
     testImplementation("org.mapdb:mapdb:latest.release")
     testImplementation("guru.nidi:graphviz-java:latest.release")
+    testImplementation("org.junit-pioneer:junit-pioneer:2.0.0")
 
     testRuntimeOnly("org.mapdb:mapdb:latest.release")
     testRuntimeOnly(project(":rewrite-java-17"))

rewrite-maven/src/main/java/org/openrewrite/maven/internal/MavenPomDownloader.java

@@ -146,6 +146,11 @@ public MavenPomDownloader(Map<Path, Pom> projectPoms, HttpSender httpSender, Exe
         this.mirrors = this.ctx.getMirrors(this.ctx.getSettings());
     }
 
+    private boolean allowPomDownloadFailure() {
+        final String propertyValue = System.getProperty("org.openrewrite.allowPomDownloadFailure");
+        return propertyValue != null && !propertyValue.equalsIgnoreCase("false");
+    }
+
     byte[] sendRequest(HttpSender.Request request) throws IOException, HttpSenderResponseException {
         long start = System.nanoTime();
         try {
@@ -633,8 +638,13 @@ public Pom download(GroupArtifactVersion gav,
         }
         ctx.getResolutionListener().downloadError(gav, uris, (containingPom == null) ? null : containingPom.getRequested());
         sample.stop(timer.tags("outcome", "unavailable").register(Metrics.globalRegistry));
-        throw new MavenDownloadingException("Unable to download POM: " + gav + '.', null, originalGav)
-                .setRepositoryResponses(repositoryResponses);
+        if (allowPomDownloadFailure()) {
+            ResolvedGroupArtifactVersion dummy = new ResolvedGroupArtifactVersion(null, gav.getGroupId(), gav.getArtifactId(), gav.getVersion(), null);
+            return new Pom(null, null, null, dummy, null, null, null, null, null, null, null, null, null, null, null, null, null);
+        } else {
+            throw new MavenDownloadingException("Unable to download POM: " + gav + '.', null, originalGav)
+                    .setRepositoryResponses(repositoryResponses);
+        }
     }
 
     /**

rewrite-maven/src/test/java/org/openrewrite/maven/internal/MavenPomDownloaderTest.java

@@ -30,6 +30,7 @@
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.CsvSource;
 import org.junit.jupiter.params.provider.ValueSource;
+import org.junitpioneer.jupiter.SetSystemProperty;
 import org.openrewrite.*;
 import org.openrewrite.ipc.http.HttpSender;
 import org.openrewrite.ipc.http.HttpUrlConnectionSender;
@@ -573,6 +574,24 @@ void skipsLocalInvalidArtifactsEmptyJar(@TempDir Path localRepository) throws IO
                 .download(new GroupArtifactVersion("com.bad", "bad-artifact", "1"), null, null, List.of(mavenLocal)));
         }
 
+        @Test
+        @SetSystemProperty(key = "org.openrewrite.allowPomDownloadFailure", value = "true")
+        void allowPomDowloadFailure(@TempDir Path localRepository) throws IOException, MavenDownloadingException {
+            MavenRepository mavenLocal = MavenRepository.builder()
+              .id("local")
+              .uri(localRepository.toUri().toString())
+              .snapshots(false)
+              .knownToExist(true)
+              .build();
+
+            // Do not throw exception
+            var result = new MavenPomDownloader(emptyMap(), ctx).download(new GroupArtifactVersion("com.some", "some-artifact", "1"), null, null, List.of(mavenLocal));
+
+            assertThat(result.getGav().getGroupId()).isEqualTo("com.some");
+            assertThat(result.getGav().getArtifactId()).isEqualTo("some-artifact");
+            assertThat(result.getGav().getVersion()).isEqualTo("1");
+        }
+
         @Test
         void doNotRenameRepoForCustomMavenLocal(@TempDir Path tempDir) throws MavenDownloadingException, IOException {
             GroupArtifactVersion gav = createArtifact(tempDir);