feat: DIREGAPIC initial implementation (#746)

ntegration tests (compute_small) are not present in this commit, as they depend on #743 and #744. Also, as a prerequisite, at least a basic implementation of DIREGAPIC must be merged in gapic-generator-java, to integrate it with [googleapis-discovery](https://github.com/googleapis/googleapis-discovery) first (since integration test infra depends on the actual googleapis/googleapis-discovery targets). Please check vam-google@8983e23 to see how it would look like with compute integration tests not excluded.


`compliance.proto` is used as a basis for the REST composer tests. It was copied as is from [showcase/compliance.proto](https://github.com/googleapis/gapic-showcase/blob/master/schema/google/showcase/v1beta1/compliance.proto).

Changes in `WORKSPACE` and `repositories.bzl` are necessary to make this repo work with gax-java `1.63.0` and above (`gax-java` vs `gapic-generator-java` java dependencies imports precedence). The other dependencies changes are either to bring deps in sync with the actual ones in googleapis, or to fix a specific import precedence issue.

I also added (in a form of bazel rules) a proto descriptor dumper and a runner from the dumped file (for debugging purposes). Not technically required here (but was very helpful for debugging purposes, so hopefully we can preserve it).

WORKSPACE

@@ -1,6 +1,7 @@
 workspace(name = "gapic_generator_java")
 
 load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+load("@bazel_tools//tools/build_defs/repo:jvm.bzl", "jvm_maven_import_external")
 
 # DO NOT REMOVE.
 # This is needed to clobber any transitively-pulled in versions of bazel_skylib so that packages
@@ -14,6 +15,36 @@ http_archive(
     ],
 )
 
+jvm_maven_import_external(
+    name = "google_java_format_all_deps",
+    artifact = "com.google.googlejavaformat:google-java-format:jar:all-deps:1.7",
+    server_urls = ["https://repo.maven.apache.org/maven2/", "http://repo1.maven.org/maven2/"],
+    licenses = ["notice", "reciprocal"]
+)
+
+# gax-java and its transitive dependencies must be imported before
+# gapic-generator-java dependencies to match the order in googleapis repository,
+# which in its turn, prioritizes actual generated clients runtime dependencies
+# over the generator dependencies.
+_gax_java_version = "1.64.0"
+
+http_archive(
+    name = "com_google_api_gax_java",
+    strip_prefix = "gax-java-%s" % _gax_java_version,
+    urls = ["https://github.com/googleapis/gax-java/archive/v%s.zip" % _gax_java_version],
+)
+
+load("@com_google_api_gax_java//:repository_rules.bzl", "com_google_api_gax_java_properties")
+
+com_google_api_gax_java_properties(
+    name = "com_google_api_gax_java_properties",
+    file = "@com_google_api_gax_java//:dependencies.properties",
+)
+
+load("@com_google_api_gax_java//:repositories.bzl", "com_google_api_gax_java_repositories")
+
+com_google_api_gax_java_repositories()
+
 load("//:repository_rules.bzl", "gapic_generator_java_properties")
 
 gapic_generator_java_properties(
@@ -35,8 +66,8 @@ protobuf_deps()
 # Import the monolith so we can transitively use its gapic rules for googleapis.
 http_archive(
     name = "com_google_api_codegen",
-    strip_prefix = "gapic-generator-2.4.6",
-    urls = ["https://github.com/googleapis/gapic-generator/archive/v2.4.6.zip"],
+    strip_prefix = "gapic-generator-2.11.1",
+    urls = ["https://github.com/googleapis/gapic-generator/archive/v2.11.1.zip"],
 )
 
 load("@com_google_googleapis//:repository_rules.bzl", "switched_rules_by_language")
@@ -48,25 +79,12 @@ switched_rules_by_language(
     java = True,
 )
 
-_gax_java_version = PROPERTIES["version.com_google_gax_java"]
-
-http_archive(
-    name = "com_google_api_gax_java",
-    strip_prefix = "gax-java-%s" % _gax_java_version,
-    urls = ["https://github.com/googleapis/gax-java/archive/v%s.zip" % _gax_java_version],
-)
-
-load("@com_google_api_gax_java//:repository_rules.bzl", "com_google_api_gax_java_properties")
-
-com_google_api_gax_java_properties(
-    name = "com_google_api_gax_java_properties",
-    file = "@com_google_api_gax_java//:dependencies.properties",
-)
-
-load("@com_google_api_gax_java//:repositories.bzl", "com_google_api_gax_java_repositories")
-
-com_google_api_gax_java_repositories()
-
 load("@io_grpc_grpc_java//:repositories.bzl", "grpc_java_repositories")
 
 grpc_java_repositories()
+
+http_archive(
+    name = "com_google_disco_to_proto3_converter",
+    strip_prefix = "disco-to-proto3-converter-1839f6aca5e968e59b7acc03e7018b0fda8c480b",
+    urls = ["https://github.com/googleapis/disco-to-proto3-converter/archive/1839f6aca5e968e59b7acc03e7018b0fda8c480b.zip"],
+)

dependencies.properties

@@ -7,11 +7,10 @@
 # Target workspace name: com_google_api_codegen
 
 # Versions only, for dependencies which actual artifacts differ between Bazel and Gradle
-version.com_google_protobuf=3.13.0
+version.com_google_protobuf=3.15.2
 # Version of google-java-format is downgraded from 1.8 to 1.7, because 1.8 supports java 11 minimum, while our JRE is java 8.
 version.google_java_format=1.7
 version.com_google_api_common_java=1.9.3
-version.com_google_gax_java=1.62.0
 version.io_grpc_java=1.30.2
 
 # Common deps.
@@ -20,7 +19,7 @@ maven.com_google_code_findbugs_jsr305=com.google.code.findbugs:jsr305:3.0.0
 maven.com_google_auto_value_auto_value=com.google.auto.value:auto-value:1.7.2
 maven.com_google_auto_value_auto_value_annotations=com.google.auto.value:auto-value-annotations:1.7.2
 maven.com_google_code_gson=com.google.code.gson:gson:2.8.6
-maven.com_google_protobuf_protobuf_java=com.google.protobuf:protobuf-java:3.12.2
+maven.com_google_protobuf_protobuf_java=com.google.protobuf:protobuf-java:3.15.8
 maven.io_github_java_diff_utils=io.github.java-diff-utils:java-diff-utils:4.0
 maven.javax_annotation_javax_annotation_api=javax.annotation:javax.annotation-api:1.3.2
 maven.javax_validation_javax_validation_api=javax.validation:validation-api:2.0.1.Final

rules_java_gapic/java_gapic.bzl

@@ -127,12 +127,17 @@ def java_gapic_library(
         service_yaml = None,
         deps = [],
         test_deps = [],
+        # possible values are: "grpc", "rest", "grpc+rest"
+        transport = None,
+        # Can be used to provide a java_library with a customized generator,
+        # like the one which dumps descriptor to a file for future debugging.
+        _java_generator_name = "java_gapic",
         **kwargs):
     file_args_dict = {}
 
     if grpc_service_config:
         file_args_dict[grpc_service_config] = "grpc-service-config"
-    else:
+    elif transport != "rest":
         for keyword in NO_GRPC_CONFIG_ALLOWLIST:
             if keyword not in name:
                 fail("Missing a gRPC service config file")
@@ -157,12 +162,15 @@ def java_gapic_library(
     srcjar_name = name + "_srcjar"
     raw_srcjar_name = srcjar_name + "_raw"
     output_suffix = ".srcjar"
+    opt_args = []
+
+    if transport:
+        opt_args.append("transport=%s" % transport)
 
     # Produces the GAPIC metadata file if this flag is set. to any value.
     # Protoc invocation: --java_gapic_opt=metadata
     plugin_args = ["metadata"]
 
-    _java_generator_name = "java_gapic"
     proto_custom_library(
         name = raw_srcjar_name,
         deps = srcs,
@@ -172,6 +180,7 @@ def java_gapic_library(
         opt_file_args = file_args_dict,
         output_type = _java_generator_name,
         output_suffix = output_suffix,
+        opt_args = opt_args,
         **kwargs
     )
 
@@ -201,10 +210,7 @@ def java_gapic_library(
         "@com_google_protobuf//:protobuf_java",
         "@com_google_api_api_common//jar",
         "@com_google_api_gax_java//gax:gax",
-        "@com_google_api_gax_java//gax-grpc:gax_grpc",
         "@com_google_guava_guava//jar",
-        "@io_grpc_grpc_java//core:core",
-        "@io_grpc_grpc_java//protobuf:protobuf",
         "@com_google_code_findbugs_jsr305//jar",
         "@org_threeten_threetenbp//jar",
         "@io_opencensus_opencensus_api//jar",
@@ -214,6 +220,17 @@ def java_gapic_library(
         "@javax_annotation_javax_annotation_api//jar",
     ]
 
+    if transport == "rest":
+        actual_deps += [
+            "@com_google_api_gax_java//gax-httpjson:gax_httpjson",
+        ]
+    else:
+        actual_deps += [
+            "@com_google_api_gax_java//gax-grpc:gax_grpc",
+            "@io_grpc_grpc_java//core:core",
+            "@io_grpc_grpc_java//protobuf:protobuf",
+        ]
+
     native.java_library(
         name = name,
         srcs = ["%s.srcjar" % srcjar_name],
@@ -224,15 +241,24 @@ def java_gapic_library(
     # Test deps.
     actual_test_deps = [
         "@com_google_googleapis//google/type:type_java_proto",  # Commonly used.
-        "@com_google_api_gax_java//gax-grpc:gax_grpc_testlib",
         "@com_google_api_gax_java//gax:gax_testlib",
         "@com_google_code_gson_gson//jar",
-        "@io_grpc_grpc_java//auth:auth",
-        "@io_grpc_grpc_netty_shaded//jar",
-        "@io_grpc_grpc_java//stub:stub",
-        "@io_opencensus_opencensus_contrib_grpc_metrics//jar",
         "@junit_junit//jar",
     ]
+
+    if transport == "rest":
+        actual_test_deps += [
+            "@com_google_api_gax_java//gax-httpjson:gax_httpjson_testlib",
+        ]
+    else:
+        actual_test_deps += [
+            "@com_google_api_gax_java//gax-grpc:gax_grpc_testlib",
+            "@io_grpc_grpc_java//auth:auth",
+            "@io_grpc_grpc_netty_shaded//jar",
+            "@io_grpc_grpc_java//stub:stub",
+            "@io_opencensus_opencensus_contrib_grpc_metrics//jar",
+        ]
+
     _append_dep_without_duplicates(actual_test_deps, test_deps)
     _append_dep_without_duplicates(actual_test_deps, actual_deps)
 

rules_java_gapic/java_gapic_pkg.bzl

@@ -301,6 +301,7 @@ def java_gapic_assembly_gradle_pkg(
         name,
         deps,
         assembly_name = None,
+        transport = None,
         **kwargs):
     package_dir = name
     if assembly_name:
@@ -350,9 +351,14 @@ def java_gapic_assembly_gradle_pkg(
         grpc_target_dep = ["%s" % grpc_target]
 
     if client_deps:
+        if transport == "rest":
+            template_label = Label("//rules_java_gapic:resources/gradle/client_rest.gradle.tmpl")
+        else:
+            template_label = Label("//rules_java_gapic:resources/gradle/client_grpc.gradle.tmpl")
+
         _java_gapic_gradle_pkg(
             name = client_target,
-            template_label = Label("//rules_java_gapic:resources/gradle/client.gradle.tmpl"),
+            template_label = template_label,
             deps = proto_target_dep + client_deps,
             test_deps = grpc_target_dep + client_test_deps,
             **kwargs

rules_java_gapic/resources/gradle/client_rest.gradle.tmpl

@@ -0,0 +1,60 @@
+buildscript {
+  repositories {
+    mavenCentral()
+  }
+}
+
+apply plugin: 'java'
+
+description = 'GAPIC library for {{name}}'
+group = 'com.google.cloud'
+version = (findProperty('version') == 'unspecified') ? '0.0.0-SNAPSHOT' : version
+sourceCompatibility = 1.7
+targetCompatibility = 1.7
+
+repositories {
+  mavenCentral()
+  mavenLocal()
+}
+
+compileJava.options.encoding = 'UTF-8'
+javadoc.options.encoding = 'UTF-8'
+
+dependencies {
+  compile 'com.google.api:gax:{{version.gax}}'
+  testCompile 'com.google.api:gax:{{version.gax}}:testlib'
+  compile 'com.google.api:gax-httpjson:{{version.gax_httpjson}}'
+  testCompile 'com.google.api:gax-httpjson:{{version.gax_httpjson}}:testlib'
+  testCompile '{{maven.junit_junit}}'
+  {{extra_deps}}
+}
+
+task smokeTest(type: Test) {
+  filter {
+    includeTestsMatching "*SmokeTest"
+    setFailOnNoMatchingTests false
+  }
+}
+
+test {
+  exclude "**/*SmokeTest*"
+}
+
+sourceSets {
+  main {
+    java {
+      srcDir 'src/main/java'
+    }
+  }
+}
+
+clean {
+  delete 'all-jars'
+}
+
+task allJars(type: Copy) {
+  dependsOn test, jar
+  into 'all-jars'
+  // Replace with `from configurations.testRuntime, jar` to include test dependencies
+  from configurations.runtime, jar
+}

src/main/java/com/google/api/generator/gapic/composer/BUILD.bazel

@@ -21,6 +21,7 @@ java_library(
         "//src/main/java/com/google/api/generator/gapic/composer/common",
         "//src/main/java/com/google/api/generator/gapic/composer/defaultvalue",
         "//src/main/java/com/google/api/generator/gapic/composer/grpc",
+        "//src/main/java/com/google/api/generator/gapic/composer/rest",
         "//src/main/java/com/google/api/generator/gapic/composer/resourcename",
         "//src/main/java/com/google/api/generator/gapic/composer/samplecode",
         "//src/main/java/com/google/api/generator/gapic/composer/store",

src/main/java/com/google/api/generator/gapic/composer/Composer.java

@@ -27,12 +27,15 @@
 import com.google.api.generator.gapic.composer.grpc.ServiceSettingsClassComposer;
 import com.google.api.generator.gapic.composer.grpc.ServiceStubSettingsClassComposer;
 import com.google.api.generator.gapic.composer.resourcename.ResourceNameHelperClassComposer;
+import com.google.api.generator.gapic.composer.rest.HttpJsonServiceCallableFactoryClassComposer;
+import com.google.api.generator.gapic.composer.rest.HttpJsonServiceStubClassComposer;
 import com.google.api.generator.gapic.model.GapicClass;
 import com.google.api.generator.gapic.model.GapicClass.Kind;
 import com.google.api.generator.gapic.model.GapicContext;
 import com.google.api.generator.gapic.model.GapicPackageInfo;
 import com.google.api.generator.gapic.model.ResourceName;
 import com.google.api.generator.gapic.model.Service;
+import com.google.api.generator.gapic.model.Transport;
 import com.google.common.annotations.VisibleForTesting;
 import java.util.ArrayList;
 import java.util.List;
@@ -80,9 +83,20 @@ public static List<GapicClass> generateStubClasses(GapicContext context) {
         .forEach(
             s -> {
               clazzes.add(ServiceStubClassComposer.instance().generate(context, s));
-              clazzes.add(ServiceStubSettingsClassComposer.instance().generate(context, s));
-              clazzes.add(GrpcServiceCallableFactoryClassComposer.instance().generate(context, s));
-              clazzes.add(GrpcServiceStubClassComposer.instance().generate(context, s));
+              if (context.transport() == Transport.REST) {
+                clazzes.add(
+                    com.google.api.generator.gapic.composer.rest.ServiceStubSettingsClassComposer
+                        .instance()
+                        .generate(context, s));
+                clazzes.add(
+                    HttpJsonServiceCallableFactoryClassComposer.instance().generate(context, s));
+                clazzes.add(HttpJsonServiceStubClassComposer.instance().generate(context, s));
+              } else {
+                clazzes.add(ServiceStubSettingsClassComposer.instance().generate(context, s));
+                clazzes.add(
+                    GrpcServiceCallableFactoryClassComposer.instance().generate(context, s));
+                clazzes.add(GrpcServiceStubClassComposer.instance().generate(context, s));
+              }
             });
     return clazzes;
   }
@@ -94,7 +108,14 @@ public static List<GapicClass> generateClientSettingsClasses(GapicContext contex
         .forEach(
             s -> {
               clazzes.add(ServiceClientClassComposer.instance().generate(context, s));
-              clazzes.add(ServiceSettingsClassComposer.instance().generate(context, s));
+              if (context.transport() == Transport.REST) {
+                clazzes.add(
+                    com.google.api.generator.gapic.composer.rest.ServiceSettingsClassComposer
+                        .instance()
+                        .generate(context, s));
+              } else {
+                clazzes.add(ServiceSettingsClassComposer.instance().generate(context, s));
+              }
             });
     return clazzes;
   }
@@ -103,15 +124,28 @@ public static List<GapicClass> generateMockClasses(GapicContext context, List<Se
     List<GapicClass> clazzes = new ArrayList<>();
     services.forEach(
         s -> {
-          clazzes.add(MockServiceClassComposer.instance().generate(context, s));
-          clazzes.add(MockServiceImplClassComposer.instance().generate(context, s));
+          if (context.transport() == Transport.REST) {
+            // REST transport tests donot not use mock services.
+          } else {
+            clazzes.add(MockServiceClassComposer.instance().generate(context, s));
+            clazzes.add(MockServiceImplClassComposer.instance().generate(context, s));
+          }
         });
     return clazzes;
   }
 
   public static List<GapicClass> generateTestClasses(GapicContext context) {
     return context.services().stream()
-        .map(s -> ServiceClientTestClassComposer.instance().generate(context, s))
+        .map(
+            s -> {
+              if (context.transport() == Transport.REST) {
+                return com.google.api.generator.gapic.composer.rest.ServiceClientTestClassComposer
+                    .instance()
+                    .generate(context, s);
+              } else {
+                return ServiceClientTestClassComposer.instance().generate(context, s);
+              }
+            })
         .collect(Collectors.toList());
   }