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One SDK to rule them all, and in the codegen bind them

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# SDK Codegen

This Looker Open Source repository is released under the MIT license. By using
this repository, you agree to the terms of that license, and acknowledge that
you are doing so at your own risk.

While Looker has developed and tested this code internally, we cannot guarantee
that the open-source tools used by the scripts in this repository have not been
modified with malicious code.

**Important** - If you are using the Looker TypeScript SDK, please see this
[note on npmjs.com](https://www.npmjs.com/package/@looker/sdk#typescript-sdk-packages) explaining changes to dependencies and packaging.

### Support

The TypeScript and Python SDKs are officially supported by Looker/Google.
Issues can be logged here in the GitHub Issues page, but can also be logged
with Looker Support. The other language SDKs are community supported. Issues
for these should be logged only in the GitHub Issues page. Details of Looker
API and SDK support can be found at [https://cloud.google.com/looker/docs/api-sdk-support-policy](https://cloud.google.com/looker/docs/api-sdk-support-policy).

## Overview

This repository contains:

- The [SDK code generator](packages/sdk-codegen) that generates the source code for Looker SDKs
- Source code for the Looker SDKs produced by the code generator
- Looker SDK source code [examples](examples)
- the [API Explorer extension](packages/extension-api-explorer) that can be installed into a Looker instance
- the stand-alone [API Explorer](packages/api-explorer)
- the [RunIt](packages/run-it) REST client tester (embedded within API Explorer, typically)
- [code generator scripts](packages/sdk-codegen-scripts) that require Node (file i/o) to read and write SDK files

## The parts of the Looker SDK

We hope to help people who want to use Looker as a platform get up and running
quickly, largely by providing pre-built client SDKs in the most popular
languages, and implementing consistency across all languages and platforms.

The Looker SDK has several parts:

- The **Looker API**, described by an [OpenAPI
  specification](https://github.com/OAI/OpenAPI-Specification) (e.g., the
  Swagger 2.x representation found at
  `https://<your-looker-domain>:19999/api/4.0/swagger.json`). The 4.0 API is
  our current & stable API. As of October 2023, [3.x has been removed](https://cloud.google.com/looker/docs/api-3x-deprecation).

- The **Looker API Explorer**, an interactive reference, accessible either
  stand-alone at
  [developers.looker.com/api/explorer/](https://developers.looker.com/api/explorer/),
  or installable into your Looker instance as an extension from the Looker
  Marketplace.

- **Language SDKs**, "smarter" client language classes and methods to improve
  the experience of calling the Looker API in various popular coding languages.
  Some SDKs are
  [Looker-supported](https://cloud.google.com/looker/docs/api-sdk-support-policy)
  whereas others are community-supported.

## SDK Versions

The 4.0 version of the API is the current and stable version of the API. The 3.x API has now been
[removed](https://cloud.google.com/looker/docs/api-3x-deprecation).

For self-hosted instances on older versions of Looker, please use the corresponding release of `sdk-codegen`` to use API 3.x.

Note: API credentials have not been changed between API 3.x and API 4 and may continue to be referred to as "API3" credentials in the Looker UI, docs, or elsewhere.

## Automatic URL encoding for input values

TL;DR: don't URL encode your inputs because the SDKs will automatically handle
it.

All SDKs URL encode (also known as [percent
encoding](https://en.wikipedia.org/wiki/Percent-encoding)) input values for
passing to the API endpoints automatically. Furthermore, except for Swift,
which has problematic URL decoding support, the other SDKs will avoid
double-encoding inputs that may already be encoded.

## Using existing, pre-generated SDKs

When a specific language SDK has been developed, Looker makes that SDK
available using the standard package manager for that platform. Currently, the
[Python SDK](python) and the [TypeScript SDK](packages/sdk) can be installed
from their respective package managers by following the instructions in their
readmes.

For the other SDKs in this repository, you can copy and paste the source code
into a module for your own project. Every SDK will eventually have a deployed
package version.

If you want to use the generation options for an SDK, read on.

## Generating an API language binding

There are three steps for generating an SDK with this project:

- [configure a `looker.ini` file](#configuring-lookerini-or-env) so the Looker
  API specification can be retrieved from your Looker server.

- **Note**: previous versions of the `looker.ini` file had an `api_version`
    entry. This is no longer required. The code generator project will read an
    `api_versions` value if that is found, but the SDKs ignore this value. If
    `api_versions` is not found in the `ini` file, it defaults to "4.0" for
    the generator to produce the definitions for the supported API versions.

- install the code generator project dependencies by running:

```sh
yarn install
yarn build
```

The resources required to run the code generator are in [package.json](package.json).

**Note**: If `yarn` is not installed, use [these instructions to install](https://yarnpkg.com/lang/en/docs/install/) it.

- run the SDK generator with `yarn gen [language]`

- **Note**: [Generating Client SDKs for the Looker API](https://www.googlecloudcommunity.com/gc/Developing-Applications/Generating-Client-SDKs-for-the-Looker-API/td-p/574683) describes the legacy, manual steps for generating an API language binding. This project replaces these manual steps, and uses an improved code generator.

## Configuring `looker.ini` or `.env`

The code generator and other scripts and tests read a configuration file called
`looker.ini` to fetch the API specification from a server. This configuration
file needs to be in the root folder of the code generator.

To create `looker.ini`, copy [`looker-sample.ini`](looker-sample.ini) to
`looker.ini` and fill in the required values. The values for `client_id` and
`client_secret` can be retrieved by navigating to
`https://<your_looker_endpoint>/admin/users`, editing your user, editing API
keys, and clicking the "reveal" button to view your `client_id` and
`client_secret`. If there are currently no API credentials, they can be
generated by clicking “New API Key.”

For your own source code repositories, be sure to configure your version
control system to ignore the SDK configuration `.ini` file so it doesn't
accidentally get published somewhere unauthorized people can see it.

Unlike some other OpenAPI code generators, the Looker SDK code generator
**never** writes access information into SDK source code. All SDKs provided by
Looker are designed to receive the credentials required to call API methods via
a `readConfig()` method that returns a key/value collection, where `client_id`
and `client_secret` are retrieved, and used only for the time it takes to
complete a login for authentication token retrieval, then they are immediately
discarded from memory.

**Note**: If a `.env` file is found, this will override values from
`looker.ini`. To use a `.env` file for configuration instead, copy
[`env-sample`](env-sample) to `.env` and provide the correct values for the
environment variables.

Invoke the SDK code generator with the command:

```sh
yarn gen
```

To always use the latest Looker API specification for SDK generation, use:

```sh
yarn wipe && yarn gen
```

The code generator will:

- read the Looker API configuration(s) from the `looker.ini` file.

- **Note**: Normally there should only be one (1) entry in `looker.ini`. This
    first ini section is what is used for the SDKs by default, and also by the
    code generator.

- download (if the API specification file is not already present) the Looker
  API specification file(s) from the configured Looker server(s)

- convert (if the converted file is not already present) the downloaded Swagger
  2 specification file(s) to OpenAPI 3.x

- validate the OpenAPI 3.x file(s)

- by default, call the code generator for each active language

- To generate one specific language SDK, use `yarn gen {language}`. The
    supported languages have a factory declared in the `Generators` array in
    [`codeGenerators.ts`](packages/sdk-codegen/src/codeGenerators.ts)

When the generator completes successfully, the output will be similar to:

```plain-text
python
  looker
    rtl
      (run-time library hand-written files here)
    sdk
      methods.py (automatically generated)
      models.py (automatically generated)
```

**Note:** If you're unable to download the API specification file because
you're using an instance of Looker that is self-signed and errors are thrown,
you can explicitly turn off SSL verification by putting `verify_ssl=false` in
the `looker.ini` file configuration section.

### Using the Legacy generator

To generate a language currently not supported by Looker's SDK code generator
with the OpenAPI generator:

- configure the desired language in [`codeGenerators.ts`](packages/sdk-codegen/src/codeGenerators.ts).

- use `yarn legacy` to call the OpenAPI generator. This will use the OpenAPI
  generator to output files to the `./api/*` path

### Additional scripts

Use

```sh
yarn run
```

to see the list of all scripts that can be run by the code generator.

After generation, the generated code might not conform with the code standards.
Changes cannot be committed until they pass the lint tests.
This can be checked with the following:

```sh
yarn lint
```

For a faster run, only the modified files can be checked with any of these
commands:

```sh
yarn lint-changed
yarn lint -q
yarn lint --quick
```

Fixes can automagically be applied with one of the following:

```sh
yarn lint-changed-fix
yarn lint -q -f
yarn lint --quick --fix
```

## SDK Examples

The [examples directory](/examples) contains code snippets and projects written
using the Looker language SDKs. You may find useful code in that repository.
and are also welcome to contribute additional examples.

## API Troubleshooting

See the official documentation for [API Troubleshooting](https://cloud.google.com/looker/docs/api-troubleshooting) suggestions.

## Notes

In addition to swagger being deprecated, this [visual guide](https://blog.readme.io/an-example-filled-guide-to-swagger-3-2/) shows why OpenAPI 3.x is preferred to Swagger 2.x.

## Securing your SDK credentials

Looker improves on the security of the generated code for SDKs by **never**
storing your server location or API credentials in the source code generated by
the Looker code generator. The SDKs also provide some customizable support for
providing API configuration values like server location and credentials to the
SDK. In every Looker SDK, there is an overrideable method called `readConfig()`
that can be customized to retrieve and return SDK configuration values from
your preferred secure storage location.

Each Looker SDK has existing `readConfig()` examples that read from `.ini`
files or environment variables. These are intended to support a quick start
when developing with a Looker SDK. If a production environment prohibits secure
use of `.ini` files or environment variables, another method of retrieving API
configuration values is required. The API configuration retrieval function
`readConfig()` can be overridden to support alternate storage scenarios.

Typically, `client_id` and `client_secret` are the only key values that will
need to be dynamically retrieved from the `readConfig()` override method
because the other configuration values are saved in memory by the initialized
SDK client. In the near future, there will be additional authentication flows
(such as OAuth) supported by Looker SDKs. The dynamic result that is returned
by `readConfig()` can also be useful in those additional scenarios.

A short [TypeScript SDK example](https://github.com/looker-open-source/sdk-examples/blob/6f7b42891923a7430e0bb8341c7b5c567a2e1269/typescript/customConfigReader.ts#L15:L28)
that customizes `readConfig()` is available in the SDK Examples repository.

There is also a Kotlin SDK unit test in this repository with a short example:

```kotlin
class MockSettings(contents: String) : ApiSettings(contents) {
    override fun readConfig(): Map<String, String> {
        return mapOf(
                "base_url" to baseUrl,
                "verify_ssl" to verifySSL.toString(),
                "timeout" to timeout.toString(),
                "headers" to headers.toString(),
                "client_id" to mockId,
                "client_secret" to mockSecret
        )
    }
}
```

Please consult with the security professionals in your organization to
determine the best way to secure your credentials for your own Looker SDK
usage.

### Warnings for using `.ini` files to configure the SDK

To streamline getting started with the Looker SDKs, support for reading SDK
credentials from an `.ini` file is included as a simple method for providing
access information (server url and API credentials) to the SDK. If the source
code to your Looker SDK application is shared in a version control system, the
`.ini` file should be ignored so it never gets inadvertently published.

If the SDK application using an `.ini` file is available publicly, download or
viewing of this `.ini` file should also be prohibited by the server hosting the
application.

### Warnings for using Environment variables to configure the SDK

If the host environment for a Looker SDK supports environment variables, the
SDK can also read environment variables to retrieve the server url and API
credentials. Environment variables could also be visible to intrusive malware
that may penetrate your application, so this option for providing credentials
should also be used with caution.

## Environment variable configuration

Environment variables can be used for any SDK runtime that supports reading
environment variables. Environment variables can be used in the:

- **Node** version of the TypeScript/JavaScript Looker SDK
- Python SDK
- Swift SDK
- Kotlin SDK
- Go SDK

The following table describes the environment variables. By default, the SDK
"namespace" is "LookerSDK" which is converted to UPPERCASE when used for naming
environment variables.

| Variable name           | Description                                                                                                                                                          |
| ----------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| LOOKERSDK_BASE_URL      | A URL like `https://my.looker.com:19999`. No default value.                                                                                                          |
| LOOKERSDK_VERIFY_SSL    | `true`, `t`, `yes`, `y`, or `1` (case insensitive) to enable SSL verification. Any other value is treated as `false`. Defaults to `true` if not set.                 |
| LOOKERSDK_TIMEOUT       | Request timeout in seconds. Defaults to `120` for most platforms.                                                                                                    |
| LOOKERSDK_CLIENT_ID     | API credentials `client_id`. This and `client_secret` must be provided in some fashion to the Node SDK, or no calls to the API will be authorized. No default value. |
| LOOKERSDK_CLIENT_SECRET | API credentials `client_secret`. No default value.                                                                                                                   |

### Configuration variable precedence

Configuration variables should be processed as follows:

- if the default configuration `.ini` file exists, apply the values
- if an environment variable exists, apply the value
- if a configuration value is explicitly in code, apply that value
- if a command-line switch is supported, apply that value

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