Report gapic generation to metadata

Metadata now looks like this:

```
{
  "sources": [
    {
      "generator": {
        "name": "artman",
        "version": "0.16.2",
        "dockerImage": "googleapis/artman@sha256:2f6b261ee7fe1aedf238991c93a20b3820de37a343d0cacf3e3e9555c2aaf2ea"
      }
    },
    {
      "template": {
        "name": "python_library",
        "origin": "synthtool.gcp",
        "version": "2018.11.28"
      }
    },
    {
      "git": {
        "name": "googleapis",
        "remote": "https://github.com/googleapis/googleapis.git",
        "sha": "58249308b9c7bd64ba18ce99100751397e5184a7",
        "internalRef": "223077517"
      }
    }
  ],
  "destinations": [
    {
      "client": {
        "source": "googleapis",
        "apiName": "vision",
        "apiVersion": "v1",
        "language": "python",
        "generator": "gapic",
        "config": "google/cloud/vision/artman_vision_v1.yaml"
      }
    }
  ]
}
```

synthtool/gcp/gapic_generator.py

@@ -18,6 +18,7 @@
 
 from synthtool import _tracked_paths
 from synthtool import log
+from synthtool import metadata
 from synthtool.gcp import artman
 from synthtool.sources import git
 
@@ -128,6 +129,15 @@ def _generate_code(
 
         log.success(f"Generated code into {genfiles}.")
 
+        metadata.add_client_destination(
+            source="googleapis" if not private else "googleapis-private",
+            api_name=service,
+            api_version=version,
+            language=language,
+            generator="gapic",
+            config=str(config_path),
+        )
+
         _tracked_paths.add(genfiles)
         return genfiles
 

synthtool/metadata.py

@@ -49,6 +49,11 @@ def add_template_source(**kwargs) -> None:
     _metadata.sources.add(template=metadata_pb2.TemplateSource(**kwargs))
 
 
+def add_client_destination(**kwargs) -> None:
+    """Adds a client library destination to the current metadata."""
+    _metadata.destinations.add(client=metadata_pb2.ClientDestination(**kwargs))
+
+
 def write(outfile: str = "synth.metadata") -> None:
     """Writes out the metadata to a file."""
     jsonified = google.protobuf.json_format.MessageToJson(_metadata)

synthtool/protos/metadata.proto

@@ -64,12 +64,17 @@ message Destination {
 }
 
 message ClientDestination {
-    string api_name = 1;
-    string api_version = 2;
-    string generator = 3;
-    string source = 4;
+    string source = 1;
+    string api_name = 2;
+    string api_version = 3;
+    string language = 4;
+    string generator = 5;
+    string config = 6;
 }
 
+// Currently unused as storing all file destination options will likely cause
+// the metadata file to be too large and may cause autosynth trashing. We'll
+// investigate using this in the future.
 message FileSetDestination {
     string source = 1;
     repeated string files = 2;

tests/test_metadata.py

@@ -40,6 +40,39 @@ def test_add_generator_source():
     assert current.sources[0].generator.version == "1.2.3"
 
 
+def test_add_template_source():
+    metadata.reset()
+
+    metadata.add_template_source(name="name", version="1.2.3")
+
+    current = metadata.get()
+
+    assert current.sources[0].template.name == "name"
+    assert current.sources[0].template.version == "1.2.3"
+
+
+def test_add_client_destination():
+    metadata.reset()
+
+    metadata.add_client_destination(
+        source="source",
+        api_name="api",
+        api_version="v1",
+        language="py",
+        generator="gen",
+        config="config",
+    )
+
+    current = metadata.get()
+
+    assert current.destinations[0].client.source == "source"
+    assert current.destinations[0].client.api_name == "api"
+    assert current.destinations[0].client.api_version == "v1"
+    assert current.destinations[0].client.language == "py"
+    assert current.destinations[0].client.generator == "gen"
+    assert current.destinations[0].client.config == "config"
+
+
 def test_write(tmpdir):
     metadata.reset()