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Migrating to google-cloud-translate 3.0

The 3.0 release of the google-cloud-translate client is a significant upgrade based on a next-gen code generator, and includes substantial interface changes. Existing code written for earlier versions of this library will likely require updates to use this version. This document describes the changes that have been made, and what you need to do to update your usage.

To summarize:

• The library has been broken out into three libraries. The new gems google-cloud-translate-v2 and google-cloud-translate-v3 contain the actual client classes for versions V2 and V3 of the Translation service, and the gem google-cloud-translate now simply provides a convenience wrapper. See Library Structure for more info.
• When creating V3 client objects, you customize the configuration in a block instead of passing arguments to the constructor. See Creating Clients for more info. When creating V2 clients, however, pass settings arguments as before.
• Previously, positional arguments were used to indicate required arguments. Now, in the V3 client, all method arguments are keyword arguments, with documentation that specifies whether they are required or optional. Additionally, you can pass a proto request object instead of separate arguments. See Passing Arguments for more info. V2 client methods, however, remain unchanged.
• Previously, some V3 client classes included class methods for constructing resource paths. These paths are now instance methods on the client objects, and are also available in a separate paths module. See Resource Path Helpers for more info.
• Previously, clients reported RPC errors by raising instances of Google::Gax::GaxError and its subclasses. Now, RPC exceptions are of type Google::Cloud::Error and its subclasses. See Handling Errors for more info.
• Some classes have moved into different namespaces. See Class Namespaces for more info.

Library Structure

Older releases of the google-cloud-translate gem were all-in-one gems that included potentially multiple clients for multiple versions of the Translation service. The Google::Cloud::Translate.new factory method would return you an instance of a Google::Cloud::Translate::V2::Api object for the V2 version of the service, or a Google::Cloud::Translate::V3::TranslationServiceClient object for the V3 version of the service. All these classes were defined in the same gem.

With the 3.0 release, the google-cloud-translate gem still provides factory methods for obtaining clients. (The method signatures will have changed. See Creating Clients for details.) However, the actual client classes have been moved into separate gems, one per service version. The Google::Cloud::Translate::V2::Api class, along with its helpers and data types, is now part of the google-cloud-translate-v2 gem. Similarly, the Google::Cloud::Translate::V3::TranslationService::Client class is part of the google-cloud-translate-v3 gem.

For normal usage, you can continue to install the google-cloud-translate gem (which will bring in the versioned client gems as dependencies) and continue to use factory methods to create clients. However, you may alternatively choose to install only one of the versioned gems. For example, if you know you will use only V2 of the service, you can install google-cloud-translate-v2 by itself, and call Google::Cloud::Translate::V2.new to create V2 clients directly.

Creating Clients

In older releases, to create a client object, you would use the Google::Cloud::Translate.new class method. Keyword arguments were available to select a service version and to configure parameters such as credentials and timeouts. Furthermore, you could configure default parameters using the Google::Cloud::Translate.configure method.

In the 3.0 release, there are separate class methods for creating clients of the modern (V3) and legacy (V2) Translation services. To create a V2 client, use the translation_v2_service class method, which takes the same keyword arguments you would have used previously. To create a V3 (or later) client, use the translation_service class method and set options in a configuration block.

Old (V3):

client = Google::Cloud::Translate.new credentials: "/path/to/credentials.json"

Old (V2):

client = Google::Cloud::Translate.new version: :v2,
                                      credentials: "/path/to/credentials.json"

New (V3):

# Call the translation_service method to create a V3 client,
# and pass a block to configure the client.
client = Google::Cloud::Translate.translation_service do |config|
  config.credentials = "/path/to/credentials.json"
end

# You can omit the block if you're keeping the default configuration
default_client = Google::Cloud::Translate.translation_service

New (V2):

# Call the separate translation_v2_service method to create a legacy V2 client,
# and pass configuration as keyword arguments.
client = Google::Cloud::Translate.translation_v2_service(
  credentials: "/path/to/credentials.json")

Passing Arguments

In older releases, required arguments would be passed as positional method arguments, while most optional arguments would be passed as keyword arguments.

With the 3.0 release, the V2 client interface remains the same, but in the V3 client interface, all RPC arguments are passed as keyword arguments, regardless of whether they are required or optional. For example:

Old (V3):

client = Google::Cloud::Translate.new

# Contents, target language, and project are positional arguments, but
# mime type is a keyword argument
response = client.translate_text ["Hello, world!"], "es", "my-project",
                                 mime_type: "text/plain"

New (V3):

client = Google::Cloud::Translate.translation_service

# All arguments are keyword arguments
response = client.translate_text content: ["Hello, world!"],
                                 target_language_code: "es",
                                 parent: "my-project",
                                 mime_type: "text/plain"

In the 3.0 release, it is also possible to pass a request object, either as a hash or as a protocol buffer.

New (V3):

client = Google::Cloud::Translate.translation_service

request = Google::Cloud::Translate::V3::TranslateTextRequest.new(
  content: ["Hello, world!"],
  target_language_code: "es",
  parent: "my-project",
  mime_type: "text/plain"
)

# Pass a request object as a positional argument:
response = client.translate_text request

Finally, in older releases, to provide call options, you would pass a Google::Gax::CallOptions object with the :options keyword argument. In the 3.0 release, pass call options using a second set of keyword arguments.

Old (V3):

client = Google::Cloud::Translate.new

options = Google::Gax::CallOptions.new timeout: 10.0

response = client.translate_text ["Hello, world!"], "es", "my-project",
                                 mime_type: "text/plain",
                                 options: options

New (V3):

client = Google::Cloud::Translate.translation_service

# Use a hash to wrap the normal call arguments (or pass a request object), and
# then add further keyword arguments for the call options.
response = client.translate_text(
  { content: ["Hello, world!"], target_language_code: "es",
    parent: "my-project", mime_type: "text/plain" },
  timeout: 10.0
)

Resource Path Helpers

The client library for the V3 service includes helper methods for generating the resource path strings passed to many calls. These helpers have changed in two ways:

• In older releases, they are class methods on the client class. In the 1.0 release, they are instance methods on the client. They are also available on a separate paths module that you can include elsewhere for convenience.
• In older releases, arguments to a resource path helper are passed as positional arguments. In the 3.0 release, they are passed as named keyword arguments.

Following is an example involving using a resource path helper.

Old (V3):

client = Google::Cloud::Translate.new

# Call the helper on the client class
name = Google::Cloud::Translate::V3::TranslationServiceClient.glossary_path(
  "my-project", "my-location", "my-glossary"
)

response = client.get_glossary name

New (V3):

client = Google::Cloud::Translate.translation_service

# Call the helper on the client instance, and use keyword arguments
name = client.glossary_path project: "my-project", location: "my-location",
                            glossary: "my-glossary"

response = client.get_glossary name: name

In the 3.0 client, you can also use the paths module as a convenience module.

New (V3):

# Bring the path methods into the current class
include Google::Cloud::Translate::V3::TranslationService::Paths

def foo
  client = Google::Cloud::Translate.translation_service

  # Call the included helper method
  name = glossary_path project: "my-project", location: "my-location",
                       glossary: "my-glossary"

  response = client.get_glossary name: name

  # Do something with response...
end

Handling Errors

The client reports standard gRPC error codes by raising exceptions. In older releases, these exceptions were located in the Google::Gax namespace and were subclasses of the Google::Gax::GaxError base exception class, defined in the google-gax gem. However, these classes were different from the standard exceptions (subclasses of Google::Cloud::Error) thrown by other client libraries such as google-cloud-storage.

The 3.0 client library now uses the Google::Cloud::Error exception hierarchy, for consistency across all the Google Cloud client libraries. In general, these exceptions have the same name as their counterparts from older releases, but are located in the Google::Cloud namespace rather than the Google::Gax namespace.

Old (V3):

client = Google::Cloud::Translate.new

begin
  response = client.translate_text ["Hello, world!"], "es", "my-project",
                                   mime_type: "text/plain"
rescue Google::Gax::Error => e
  # Handle exceptions that subclass Google::Gax::Error
end

New (V3):

client = Google::Cloud::Translate.translation_service

begin
  response = client.translate_text content: ["Hello, world!"],
                                  target_language_code: "es",
                                  parent: "my-project",
                                  mime_type: "text/plain"
rescue Google::Cloud::Error => e
  # Handle exceptions that subclass Google::Cloud::Error
end

Class Namespaces

In older releases, the client object for V3 was of class Google::Cloud::Translate::V3::TranslationServiceClient. In the 3.0 release, the client object is of class Google::Cloud::Translate::V3::TranslationService::Client. Note that most users will use the Google::Cloud::Translate.translation_service factory method to create instances of the client object, so you may not need to reference the actual class directly. See Creating Clients.

In older releases, the V3 credentials object was of class Google::Cloud::Translate::V3::Credentials. In the 3.0 release, the credentials object is of class Google::Cloud::Translate::V3::TranslationService::Credentials. Again, most users will not need to reference this class directly.

The V2 classes have not been renamed.