A generator for protocol buffer described APIs for and in Go.
This is a generator for API client libraries for APIs specified by protocol buffers, such as those inside Google. It takes a protocol buffer (with particular annotations) and uses it to generate a client library.
We aim for this generator to replace the older monolithic generator. Some areas we hope to improve over the old generator are:
- using explicit normalized format for specifying APIs,
- simpler, faster implementation, and
- better error reporting.
go get github.com/googleapis/gapic-generator-go/cmd/protoc-gen-go_gapic
.
If you are using Go 1.11 and see error cannot find main module
, see this FAQ page.
Or to install from source:
git pull https://github.com/googleapis/gapic-generator-go.git
cd gapic-generator-go
go install ./cmd/protoc-gen-go_gapic
The generator works as a protoc
plugin, get protoc
from google/protobuf.
The generator is configured via protobuf annotations found at googleapis/api-common-protos. The generator follows the guidance defined in AIP-4210.
The only required annotation to generate a client is the service annotation google.api.default_host
(here).
The value of google.api.default_host
must be just a host name, excluding a scheme. For example,
import "google/api/client.proto";
...
service Foo {
option (google.api.default_host) = "api.foo.com";
...
}
If a RPC returns a google.longrunning.Operation
, the RPC must be annotated with google.longrunning.operation_info
in accordance with AIP-151.
The Cloud Natural Language API is an example of a fully configured API that has a Go client generated by gapic-generator-go.
The supported configuration annotations include:
- Service Options
google.api.default_host
: host name used in the default service client initializationgoogle.api.oauth_scopes
: OAuth scopes needed by the client to auth'n/z
- Method Options
google.longrunning.operation_info
: used to determine response & metadata types of LRO methods
protoc -I $API_COMMON_PROTOS --go_gapic_out [OUTPUT_DIR] --go_gapic_opt 'go-gapic-package=package/path/url;name' a.proto b.proto
Note: The $API_COMMON_PROTOS
variable represents a path to the googleapis/api-common-protos directory to import the configuration annotations.
The go_gapic_opt
protoc plugin option flag is necessary to convey configuration information not present in the protos.
The plugin option's value is a key-value pair delimited by an equal sign =
.
The configuration supported by the plugin option includes:
-
go-gapic-package
: the Go package of the generated client library.- The substring preceding the semicolon is the import path of the package, e.g.
github.com/username/awesomeness
. - The substring after the semicolon is the name of the package used in the
package
statement.
Note: Idiomatically the name is last element of the path but it need not be. For instance, the last element of the path might be the package's version, and the package would benefit from a more descriptive name.
- The substring preceding the semicolon is the import path of the package, e.g.
-
module
: prefix to be stripped from thego-gapic-package
used in the generated filenames.- Note: This option is not supported from the Bazel interface.
-
grpc-service-config
: the path to a gRPC ServiceConfig JSON file.- This is used for client-side retry configuration in accordance with AIP-4221
-
release-level
: the client library release level.- Defaults to empty, which is essentially the GA release level.
- Acceptable values are
alpha
andbeta
.
-
gapic-service-config
: the path the service YAML file.- This is used for service-level client documentation.
- Note: This option is a workaround and will be deprecated.
-
sample
: path to sample configuration files.- This is used for sample generation. Refer to sample generation guide for more details.
-
gapic
: path to the legacy gapic configuration file.- This is used for sample generation only. Both gapic config itself and this option will be deprecated soon. Refer to sample generation guide for more details.
The generator can be executed via a Bazel BUILD file using the macro in this repo.
Add the following to your WORKSPACE to import this project.
load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
http_archive(
name = "com_googleapis_gapic_generator_go",
strip_prefix = "gapic-generator-go-master",
urls = ["https://github.com/googleapis/gapic-generator-go/archive/master.zip"],
)
load("@com_googleapis_gapic_generator_go//:repositories.bzl", "com_googleapis_gapic_generator_go_repositories")
com_googleapis_gapic_generator_go_repositories()
Note: do not use master
, use a commit hash or a release tag.
And invoke it in a BUILD file like so, using an example based on the googleapis repo.
load("@com_googleapis_gapic_generator_go//rules_go_gapic:go_gapic.bzl", "go_gapic_library")
go_gapic_library(
name = "language_go_gapic",
srcs = [
# BUILD target for proto_library
"//google/cloud/language/v1:language_proto",
],
deps = [
# BUILD target for go_library_proto
"//google/cloud/language/v1:language_go_proto",
],
# go-gapic-package parameter value
importpath = "cloud.google.com/go/language/apiv1;language",
)
The generator options defined in Invocation are supported as the following attributes:
-
grpc_service_config
: a label for a gRPC ServiceConfig JSON file. -
release_level
: the client library release level. -
service_yaml
: a label for a service YAML file.- Note: This option will eventually be deprecated.
-
samples
: a path to a sample config file. There can exist multiples of this. -
gapic_yaml
: path to a gapic configuration file.- Note: This config is only used to generate samples.
-
sample_only
: if present, directs the generator to forgo client generation and generate only samples.
The generator can also be executed via a Docker container. The image containes protoc
, the microgenerator
binary, and the standard API protos.
$ docker run \
--rm \
--user $UID \
--mount type=bind,source=</abs/path/to/protos>,destination=/in,readonly \
--mount type=bind,source=</abs/path/to/configs>,destination=/conf,readonly \
--mount type=bind,source=$GOPATH/src,destination=/out/ \
gcr.io/gapic-images/gapic-generator-go \
--go-gapic-package "github.com/package/import/path;name"
Replace /abs/path/to/protos
with the absolute path to the input protos and github.com/package/import/path;name
with the desired import path & name for the gapic
, as described in Invocation.
For convenience, the gapic.sh script wraps the above docker
invocation.
An equivalent invocation using gapic.sh
is:
$ gapic.sh \
--image gcr.io/gapic-images/gapic-generator-go \
--in /abs/path/to/protos \
--out $GOPATH/src \
--go-gapic-package "<github.com/package/import/path;name>"
Use gapic.sh --help
to print the usage documentation.
This is an explanation of the Go GAPIC generator for those interested in how it works and possibly those using it as a reference.
gapic-generator-go
is a protoc
plugin. It consumes a serialzed CodeGeneratorRequest
on stdin
and produces a serialized CodeGeneratorResponse
on stdout
. The CodeGeneratorResponse
contains all of the generated Go code and/or any error(s) that might of occured during generation. All logs are emitted on stderr
.
The plugin implementation can be found in cmd/protoc-gen-go_gapic.
A single invocation of the code generator creates a doc.go
file package level documentation according to godoc. This documentation is (currently) pulled from a given service config.
Each service found in the input protos gets two generated artifacts:
{service}_client.go
: contains the GAPIC implementation{service}_client_example_test.go
: contains example code for each service method, consumed by godoc
There is no directory structure in the generated output. All files are placed directly in the designated output directory by protoc
.
The generator implementation can be found in internal/gengapic.
The service client type, initialization code and any standard helpers are generated first. Then each method is generated. Any relevant helper types (i.e. pagination Iterator types, LRO helpers, etc.) for the service methods are generated following the methods.
Following the client implementation, the client example file is generated, and after all services have been generated the single doc.go
file is created.
The generator itself supports the latest version.
The generated code is compatible with Go 1.6.
If you are looking to contribute to the project, please see CONTRIBUTING.md for guidelines.