TIKA-5009: Make projectId optional in the GCS plugin

CHANGES.txt

@@ -6,6 +6,10 @@ Release 4.2.1 - unreleased
      for EKS IAM roles for service accounts (IRSA); the plugin now bundles the AWS STS
      module it needs (TIKA-5006).
 
+   * The GCS fetcher, emitter and pipes iterator no longer require projectId. When it is
+     unset, the client resolves a project from the environment, as it does for its
+     credentials (TIKA-5009).
+
   OTHER CHANGES
 
    * PEM-armored CMS/PKCS7 (-----BEGIN PKCS7----- or -----BEGIN CMS-----) is parsed like

docs/modules/ROOT/pages/pipes/plugins/gcs.adoc

@@ -47,7 +47,7 @@ The GCS plugin relies on Google's Application Default Credentials chain — ther
 * Setting the `GOOGLE_APPLICATION_CREDENTIALS` environment variable to the path of a service-account JSON key.
 * Running `gcloud auth application-default login` for local development.
 
-The `projectId` field in each component selects which GCP project to bill the API calls against; the service account or user must have storage access to the named bucket.
+`projectId` is optional. Reading, writing and listing objects needs no project, and storage access is billed to the project that owns the bucket. When unset, the client resolves a project from the environment (`GOOGLE_CLOUD_PROJECT`, the credentials file, the gcloud config or the GCE metadata server). The service account or user must have storage access to the named bucket.
 
 [#gcs-fetcher]
 == GCS Fetcher (`gcs-fetcher`)
@@ -66,8 +66,8 @@ include::example$pipes-gcs-fetcher.json[]
 |Field |Default |Description
 
 |`projectId`
-|_required_
-|GCP project ID for billing/authentication.
+|_none_
+|Optional GCP project ID. See <<credentials>>.
 
 |`bucket`
 |_required_
@@ -99,8 +99,8 @@ include::example$pipes-gcs-emitter.json[]
 |Field |Default |Description
 
 |`projectId`
-|_required_
-|GCP project ID (validated non-blank).
+|_none_
+|Optional GCP project ID. See <<credentials>>.
 
 |`bucket`
 |_required_
@@ -138,8 +138,8 @@ In addition to the required `fetcherId` / `emitterId` (see xref:pipes/iterators.
 |GCS bucket to enumerate.
 
 |`projectId`
-|`""`
-|GCP project ID for the listing API call.
+|_none_
+|Optional GCP project ID. See <<credentials>>.
 
 |`prefix`
 |`""`

tika-pipes/tika-pipes-plugins/tika-pipes-gcs/src/main/java/org/apache/tika/pipes/emitter/gcs/GCSEmitter.java

@@ -82,10 +82,11 @@ private GCSEmitter(ExtensionConfig extensionConfig, GCSEmitterConfig config, Sto
     }
 
     private static Storage buildStorage(GCSEmitterConfig config) {
-        return StorageOptions.newBuilder()
-                .setProjectId(config.projectId())
-                .build()
-                .getService();
+        StorageOptions.Builder builder = StorageOptions.newBuilder();
+        if (!StringUtils.isBlank(config.projectId())) {
+            builder.setProjectId(config.projectId());
+        }
+        return builder.build().getService();
     }
 
     @Override

tika-pipes/tika-pipes-plugins/tika-pipes-gcs/src/main/java/org/apache/tika/pipes/emitter/gcs/GCSEmitterConfig.java

@@ -34,9 +34,6 @@ public static GCSEmitterConfig load(final String json)
     }
 
     public void validate() throws TikaConfigException {
-        if (projectId == null || projectId.isBlank()) {
-            throw new TikaConfigException("'projectId' must not be empty");
-        }
         if (bucket == null || bucket.isBlank()) {
             throw new TikaConfigException("'bucket' must not be empty");
         }

tika-pipes/tika-pipes-plugins/tika-pipes-gcs/src/main/java/org/apache/tika/pipes/fetcher/gcs/GCSFetcher.java

@@ -38,9 +38,10 @@
 import org.apache.tika.pipes.fetcher.gcs.config.GCSFetcherConfig;
 import org.apache.tika.plugins.AbstractTikaExtension;
 import org.apache.tika.plugins.ExtensionConfig;
+import org.apache.tika.utils.StringUtils;
 
 /**
- * Fetches files from google cloud storage. Must set projectId and bucket via the config.
+ * Fetches files from google cloud storage. Must set bucket via the config; projectId is optional.
  */
 public class GCSFetcher extends AbstractTikaExtension implements Fetcher {
 
@@ -64,12 +65,12 @@ public static GCSFetcher build(ExtensionConfig extensionConfig) throws IOExcepti
 
     private void initialize() throws TikaConfigException {
         ConfigValidator.mustNotBeEmpty("bucket", config.getBucket());
-        ConfigValidator.mustNotBeEmpty("projectId", config.getProjectId());
 
-        storage = StorageOptions.newBuilder()
-                .setProjectId(config.getProjectId())
-                .build()
-                .getService();
+        StorageOptions.Builder builder = StorageOptions.newBuilder();
+        if (!StringUtils.isBlank(config.getProjectId())) {
+            builder.setProjectId(config.getProjectId());
+        }
+        storage = builder.build().getService();
     }
 
     @Override

tika-pipes/tika-pipes-plugins/tika-pipes-gcs/src/main/java/org/apache/tika/pipes/iterator/gcs/GCSPipesIterator.java

@@ -50,16 +50,12 @@ private GCSPipesIterator(GCSPipesIteratorConfig config, ExtensionConfig extensio
         if (StringUtils.isBlank(config.getBucket())) {
             throw new TikaConfigException("bucket must not be empty");
         }
-        if (StringUtils.isBlank(config.getProjectId())) {
-            throw new TikaConfigException("projectId must not be empty");
-        }
 
-        // Initialize the GCS client
-        this.storage = StorageOptions
-                .newBuilder()
-                .setProjectId(config.getProjectId())
-                .build()
-                .getService();
+        StorageOptions.Builder builder = StorageOptions.newBuilder();
+        if (!StringUtils.isBlank(config.getProjectId())) {
+            builder.setProjectId(config.getProjectId());
+        }
+        this.storage = builder.build().getService();
     }
 
     public static GCSPipesIterator build(ExtensionConfig extensionConfig) throws IOException, TikaConfigException {

tika-pipes/tika-pipes-plugins/tika-pipes-gcs/src/test/java/org/apache/tika/pipes/gcs/ConfigExamplesTest.java

@@ -17,6 +17,7 @@
 package org.apache.tika.pipes.gcs;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
 
 import com.fasterxml.jackson.databind.JsonNode;
 import org.junit.jupiter.api.Test;
@@ -41,7 +42,8 @@ public void testGCSFetcherConfig() throws Exception {
         JsonNode inner = innerComponent(readExample("gcs-fetcher.json"),
                 "fetchers", "gcsf", "gcs-fetcher");
         GCSFetcherConfig config = GCSFetcherConfig.load(inner.toString());
-        assertEquals("my-gcp-project", config.getProjectId());
+        // The fetcher example leaves projectId out to show it is optional.
+        assertNull(config.getProjectId());
         assertEquals("my-tika-input", config.getBucket());
     }
 

tika-pipes/tika-pipes-plugins/tika-pipes-gcs/src/test/java/org/apache/tika/pipes/gcs/GCSProjectIdTest.java

@@ -0,0 +1,86 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.tika.pipes.gcs;
+
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import org.junit.jupiter.api.Test;
+
+import org.apache.tika.exception.TikaConfigException;
+import org.apache.tika.pipes.emitter.gcs.GCSEmitter;
+import org.apache.tika.pipes.fetcher.gcs.GCSFetcher;
+import org.apache.tika.pipes.iterator.gcs.GCSPipesIterator;
+import org.apache.tika.plugins.ExtensionConfig;
+
+/**
+ * projectId is optional: reading, writing and listing objects need no project, so each
+ * component builds without one. Building makes no request, so these need no credentials.
+ */
+public class GCSProjectIdTest {
+
+    private static final String BUCKET_ONLY = "{\"bucket\": \"bucket\"}";
+    private static final String WITH_PROJECT = "{\"bucket\": \"bucket\", \"projectId\": \"project\"}";
+
+    @Test
+    public void testFetcherWithoutProjectId() throws Exception {
+        assertNotNull(GCSFetcher.build(new ExtensionConfig("gcs", "gcs-fetcher", BUCKET_ONLY)));
+    }
+
+    @Test
+    public void testFetcherWithProjectId() throws Exception {
+        assertNotNull(GCSFetcher.build(new ExtensionConfig("gcs", "gcs-fetcher", WITH_PROJECT)));
+    }
+
+    @Test
+    public void testFetcherRequiresBucket() {
+        assertThrows(TikaConfigException.class,
+                () -> GCSFetcher.build(new ExtensionConfig("gcs", "gcs-fetcher", "{}")));
+    }
+
+    @Test
+    public void testEmitterWithoutProjectId() throws Exception {
+        assertNotNull(GCSEmitter.build(new ExtensionConfig("gcs", "gcs-emitter", BUCKET_ONLY)));
+    }
+
+    @Test
+    public void testEmitterWithProjectId() throws Exception {
+        assertNotNull(GCSEmitter.build(new ExtensionConfig("gcs", "gcs-emitter", WITH_PROJECT)));
+    }
+
+    @Test
+    public void testEmitterRequiresBucket() {
+        assertThrows(TikaConfigException.class,
+                () -> GCSEmitter.build(new ExtensionConfig("gcs", "gcs-emitter", "{}")));
+    }
+
+    @Test
+    public void testIteratorWithoutProjectId() throws Exception {
+        assertNotNull(GCSPipesIterator.build(new ExtensionConfig("gcs", "gcs-pipes-iterator", BUCKET_ONLY)));
+    }
+
+    @Test
+    public void testIteratorWithProjectId() throws Exception {
+        assertNotNull(GCSPipesIterator.build(new ExtensionConfig("gcs", "gcs-pipes-iterator", WITH_PROJECT)));
+    }
+
+    @Test
+    public void testIteratorRequiresBucket() {
+        assertThrows(TikaConfigException.class,
+                () -> GCSPipesIterator.build(new ExtensionConfig("gcs", "gcs-pipes-iterator", "{}")));
+    }
+}

tika-pipes/tika-pipes-plugins/tika-pipes-gcs/src/test/resources/config-examples/gcs-fetcher.json

@@ -2,7 +2,6 @@
   "fetchers": {
     "gcsf": {
       "gcs-fetcher": {
-        "projectId": "my-gcp-project",
         "bucket": "my-tika-input",
         "extractUserMetadata": true,
         "spoolToTemp": true