fix(Bazel): Support local registries

The current implementation of Bazel only supports remote registries. This
commit extends the implementation to also support registries on the local
filesystem. They are called "Index Registries" (see [1]).

The variable "%workspace%" present in the test data is a built-in variable
of Bazel (see [2]).

[1]: https://docs.bazel.build/versions/5.1.0/bzlmod.html#index-registry
[2]: https://bazel.build/run/bazelrc#bazelrc-syntax-semantics

Signed-off-by: Nicolas Nobelis <nicolas.nobelis@bosch.com>

clients/bazel-module-registry/src/main/kotlin/BazelModuleRegistryService.kt

@@ -0,0 +1,46 @@
+/*
+ * Copyright (C) 2024 The ORT Project Authors (see <https://github.com/oss-review-toolkit/ort/blob/main/NOTICE>)
+ *
+ * Licensed 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
+ *
+ *     https://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.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ * License-Filename: LICENSE
+ */
+
+package org.ossreviewtoolkit.clients.bazelmoduleregistry
+
+import kotlinx.serialization.json.Json
+import kotlinx.serialization.json.JsonNamingStrategy
+
+/**
+ * The JSON (de-)serialization object used by this client.
+ */
+internal val JSON = Json {
+    ignoreUnknownKeys = true
+    namingStrategy = JsonNamingStrategy.SnakeCase
+}
+
+/**
+ * A Bazel registry which is either local or remote.
+ */
+interface BazelModuleRegistryService {
+    /**
+     * Retrieve the metadata for a module.
+     */
+    suspend fun getModuleMetadata(name: String): ModuleMetadata
+
+    /**
+     * Retrieve information about the source code for a specific version of a module.
+     */
+    suspend fun getModuleSourceInfo(name: String, version: String): ModuleSourceInfo
+}

clients/bazel-module-registry/src/main/kotlin/LocalBazelModuleRegistryService.kt

@@ -0,0 +1,67 @@
+/*
+ * Copyright (C) 2024 The ORT Project Authors (see <https://github.com/oss-review-toolkit/ort/blob/main/NOTICE>)
+ *
+ * Licensed 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
+ *
+ *     https://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.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ * License-Filename: LICENSE
+ */
+
+package org.ossreviewtoolkit.clients.bazelmoduleregistry
+
+import java.io.File
+
+import kotlinx.serialization.Serializable
+import kotlinx.serialization.json.decodeFromStream
+
+/**
+ * A Bazel registry which is located on the local file system.
+ */
+class LocalBazelModuleRegistryService(directory: File) : BazelModuleRegistryService {
+    private val moduleDirectory: File
+
+    init {
+        val registryFile = directory.resolve("bazel_registry.json")
+
+        require(registryFile.isFile) {
+            "The Bazel registry file bazel_registry.json does not exist in '${directory.canonicalPath}'."
+        }
+
+        val bazelRegistry = registryFile.inputStream().use {
+            JSON.decodeFromStream<BazelRegistry>(it)
+        }
+
+        moduleDirectory = registryFile.resolve(bazelRegistry.moduleBasePath)
+    }
+
+    override suspend fun getModuleMetadata(name: String): ModuleMetadata {
+        val metadataJson = moduleDirectory.resolve(name).resolve("metadata.json")
+        require(metadataJson.isFile)
+        return metadataJson.inputStream().use {
+            JSON.decodeFromStream<ModuleMetadata>(it)
+        }
+    }
+
+    override suspend fun getModuleSourceInfo(name: String, version: String): ModuleSourceInfo {
+        val sourceJson = moduleDirectory.resolve(name).resolve(version).resolve("source.json")
+        require(sourceJson.isFile)
+        return sourceJson.inputStream().use {
+            JSON.decodeFromStream<ModuleSourceInfo>(it)
+        }
+    }
+}
+
+@Serializable
+private data class BazelRegistry(
+    val moduleBasePath: String
+)

clients/bazel-module-registry/src/main/kotlin/RemoteBazelModuleRegistryService.kt

@@ -19,9 +19,6 @@
 
 package org.ossreviewtoolkit.clients.bazelmoduleregistry
 
-import kotlinx.serialization.json.Json
-import kotlinx.serialization.json.JsonNamingStrategy
-
 import okhttp3.MediaType.Companion.toMediaType
 import okhttp3.OkHttpClient
 
@@ -30,14 +27,6 @@ import retrofit2.converter.kotlinx.serialization.asConverterFactory
 import retrofit2.http.GET
 import retrofit2.http.Path
 
-/**
- * The JSON (de-)serialization object used by this client.
- */
-private val JSON = Json {
-    ignoreUnknownKeys = true
-    namingStrategy = JsonNamingStrategy.SnakeCase
-}
-
 /**
  * The client uses the Bazel Central Registry by default.
  */
@@ -47,7 +36,7 @@ private const val DEFAULT_URL = "https://bcr.bazel.build"
  * Interface for a Bazel Module Registry, based on the directory structure of https://bcr.bazel.build/ and the Git
  * repository it is based on (https://github.com/bazelbuild/bazel-central-registry/).
  */
-interface RemoteBazelModuleRegistryService {
+interface RemoteBazelModuleRegistryService : BazelModuleRegistryService {
     companion object {
         /**
          * Create a Bazel Module Registry client instance for communicating with a server running at the given [url],
@@ -72,12 +61,15 @@ interface RemoteBazelModuleRegistryService {
      * E.g. https://bcr.bazel.build/modules/glog/metadata.json.
      */
     @GET("modules/{name}/metadata.json")
-    suspend fun getModuleMetadata(@Path("name") name: String): ModuleMetadata
+    override suspend fun getModuleMetadata(@Path("name") name: String): ModuleMetadata
 
     /**
      * Retrieve information about the source code for a specific version of a module.
      * E.g. https://bcr.bazel.build/modules/glog/0.5.0/source.json.
      */
     @GET("modules/{name}/{version}/source.json")
-    suspend fun getModuleSourceInfo(@Path("name") name: String, @Path("version") version: String): ModuleSourceInfo
+    override suspend fun getModuleSourceInfo(
+        @Path("name") name: String,
+        @Path("version") version: String
+    ): ModuleSourceInfo
 }

plugins/package-managers/bazel/src/funTest/assets/projects/synthetic/bazel-local-registry/.bazelrc

@@ -0,0 +1,3 @@
+common --registry=file://%workspace%/tools/bazelbuild/registry/
+
+common --registry=https://github.com/raw/bazelbuild/bazel-central-registry/main/