## Migrating to grafeas 1.0

The 1.0 release of the grafeas client is a significant upgrade
based on a [next-gen code generator](https://github.com/googleapis/gapic-generator-ruby),
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 two libraries. The new gem
    `grafeas-v1` contains the actual client classes for version
    V1 of the Grafeas service, and the gem `grafeas` now
    simply provides a convenience wrapper. See
    [Library Structure](#library-structure) for more info.
 *  The library uses a new configuration mechanism giving you closer control
    over endpoint address, network timeouts, and retry. See
    [Client Configuration](#client-configuration) for more info. Furthermore,
    when creating a client object, you can customize its configuration in a
    block rather than passing arguments to the constructor.
    See [Creating Clients](#creating-clients) for more info.
 *  The library is now provider-agnostic, no longer defaulting to the endpoint
    and credentials for Google's implementation. You must specify the endpoint
    explicitly. If you want to use Google's Cloud Container Analysis service,
    install the `google-cloud-container_analysis` gem, which provides a
    Google-specific wrapper. See [Provider Independence](#provider-independence)
    for more info.
 *  Previously, positional arguments were used to indicate required arguments.
    Now, 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](#passing-arguments) for more info.
 *  Previously, some client classes included helper methods for constructing
    resource paths. These methods now take keyword rather than positional
    arguments, and are also available in a separate paths module. See
    [Resource Path Helpers](#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](#handling-errors) for more info.
 *  Some classes have moved into different namespaces. See
    [Class Namespaces](#class-namespaces) for more info.

### Library Structure

Older 0.x releases of the `grafeas` gem were all-in-one gems
that included potentially multiple clients for multiple versions of the
Grafeas service. The `Grafeas.new` factory method would
return you an instance of a `Grafeas::V1::GrafeasClient`
object for the V1 version of the service.

With the 1.0 release, the `grafeas` gem still provides factory
methods for obtaining clients. (The method signatures will have changed. See
[Creating Clients](#creating-clients) for details.) However, the actual client
classes have been moved into separate gems, one per service version. Currently,
Grafeas has one version, V1. The
`Grafeas::V1::Grafeas::Client` class, along with its
helpers and data types, is now part of the `grafeas-v1` gem.
If additional versions of the Grafeas service are released, additional gems
may be provided for their client classes.

For normal usage, you can continue to install the `grafeas` 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 only
use implementations of `V1` of the service, you can install `grafeas-v1` by
itself, and construct instances of the `Grafeas::V1::Grafeas::Client` client
class directly.

### Client Configuration

In older releases, if you wanted to customize performance parameters or
low-level behavior of the client (such as credentials, timeouts, or
instrumentation), you would pass a variety of keyword arguments to the client
constructor. It was also extremely difficult to customize the default settings.

With the 1.0 release, a configuration interface provides control over these
parameters, including defaults for all instances of a client, and settings for
each specific client instance. For example, to set default credentials and
timeout for all Grafeas V1 clients:

```
Grafeas::V1::Grafeas::Client.configure do |config|
  config.credentials = my_credentials
  config.timeout = 10.0
end
```

Individual RPCs can also be configured independently. For example, to set the
timeout for the `create_occurrence` call:

```
Grafeas::V1::Grafeas::Client.configure do |config|
  config.rpcs.create_occurrence.timeout = 20.0
end
```

Finally, you can override the configuration for each client instance. See the
section on [Creating Clients](#creating-clients) for details.

### Creating Clients

In older releases, to create a client object, you would use the
`Grafeas.new` class method. Keyword arguments were available to
select a service version and to configure parameters such as credentials and
timeouts.

With the 1.0 release, use the `Grafeas.grafeas` class
method to create a client object. You may select a service version using the
`:version` keyword argument. However, other configuration parameters should be
set in a configuration block when you create the client.

Old:
```
client = Grafeas.new credentials: my_credentials_object
```

New:
```
client = Grafeas.grafeas do |config|
  config.credentials = my_credentials_object
end
```

The configuration block is optional. If you do not provide it, or you do not
set some configuration parameters, then the default configuration is used. See
[Client Configuration](#client-configuration).

### Provider Independence

Older releases were tied to Google's Grafeas implementation, the Google Cloud
Container Analysis service. Clients were configured to use Google's endpoint
and credentials by default, though this could be overridden. You could also use
Google-specific credential specifications such as the path to a Google service
account keyfile.

With the 1.0 release, the `grafeas` gem is provider-independent, and does not
default to the Google implementation. You must specify an endpoint host, and
you must provide gRPC-based credentials (such as a
`GRPC::Core::ChannelCredentials` or a pre-constructed `GRPC::Core::Channel`
object) when creating a client object. These properties can be set using the
[configuration interface](#client-configuration) or by passing a block to the
constructor as covered in [Creating Clients](#creating-clients).

Old:
```
client = Grafeas.new credentials: "path/to/google/keyfile.json"
```

New:
```
client = Grafeas.grafeas do |config|
  config.endpoint = "my-grafeas.example.com"
  config.credentials = my_grpc_credentials
end

# or

client = Grafeas.grafeas do |config|
  config.credentials = my_existing_grpc_channel
end
```

If you want to continue using Google's Cloud Container Analysis implementation,
we recommend using the `google-cloud-container_analysis` gem, which provides
the Google-specific default endpoint and credentials. Using the Container
Analysis client library, you can obtain a Grafeas client object connected and
authenticated with the Google backend.

New:
```
require "google/cloud/container_analysis"

# Create a connection to the Google Container Analysis service
container_analysis = Google::Cloud::ContainerAnalysis.container_analysis do |config|
  config.credentials = "/path/to/google/keyfile.json"
end

# You can obtain a Grafeas client from the Container Analysis connection
grafeas_client = container_analysis.grafeas_client
```

### 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 1.0 release, all RPC arguments are passed as keyword arguments,
regardless of whether they are required or optional. For example:

Old:
```
client = Grafeas.new

parent = "projects/my-project"

# Parent is a positional argument, while page_size is a keyword argument.
response = client.list_occurrences parent, page_size: 10
```

New:
```
client = Grafeas.grafeas

parent = "projects/my-project"

# Parent and page_size are both keyword arguments
response = client.list_occurrences parent: parent, page_size: 10
```

In the 1.0 release, it is also possible to pass a request object, either
as a hash or as a protocol buffer.

New:
```
client = Grafeas.grafeas

request = Grafeas::V1::ListOccurrencesRequest.new(
  parent: "projects/my-project",
  page_size: 10
)

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

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

Old:
```
client = Grafeas.new

parent = "projects/my-project"

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

response = client.list_occurrences parent, page_size: 10, options: options
```

New:
```
client = Grafeas.grafeas

parent = "projects/my-project"

# 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.list_occurrences(
  { parent: parent, page_size: 10 },
  timeout: 10.0
)
```

### Resource Path Helpers

The client library 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 1.0 release, they are passed as named _keyword_
  arguments.

Following is an example involving using a resource path helper.

Old:
```
client = Grafeas.new

# Call the helper on the client class
parent = Grafeas::V1::GrafeasClient.project_path "my-project"

response = client.list_occurrences parent
```

New:
```
client = Grafeas.grafeas

# Call the helper on the client instance, and use keyword arguments
parent = client.project_path project: "my-project"

response = client.list_occurrences parent: parent
```

In the 1.0 client, you can also use the paths module as a convenience module.

New:
```
# Bring the path helper methods into the current class
include Grafeas::V1::Grafeas::Paths

def foo
  client = Grafeas.grafeas

  # Call the included helper method
  parent = project_path project: "my-project"

  response = client.list_occurrences parent: parent

  # Do something with response...
end
```

### Handling Errors

The client reports standard
{file:https://github.com/grpc/grpc/blob/master/doc/statuscodes.md 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 1.0 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:
```
client = Grafeas.new

parent = "projects/my-project"

begin
  response = client.list_occurrences parent, page_size: 10
rescue Google::Gax::Error => e
  # Handle exceptions that subclass Google::Gax::Error
end
```

New:
```
client = Grafeas.grafeas

parent = "projects/my-project"

begin
  response = client.list_occurrences parent: parent, page_size: 10
rescue Google::Cloud::Error => e
  # Handle exceptions that subclass Google::Cloud::Error
end
```

### Class Namespaces

In older releases, the client object was of classes with names like:
`Grafeas::V1::GrafeasClient`.
In the 1.0 release, the client object is of a different class:
`Grafeas::V1::Grafeas::Client`.
Note that most users will use the factory methods such as
`Grafeas.grafeas` to create instances of the client object,
so you may not need to reference the actual class directly.
See [Creating Clients](#creating-clients).

In older releases, there was a Google-specific credentials class named
`Grafeas::V1::Credentials`.
In the 1.0 release, this class is no longer present.
See [Provider Independence](#provider-independence).