Rewrite docs on how to use local glean plugin in m-c (#3033)

* Rewrite docs on how to use local glean plugin in m-c

[doc only]

Co-authored-by: Travis Long <[email protected]>

.dictionary

@@ -1,4 +1,4 @@
-personal_ws-1.1 en 294 utf-8
+personal_ws-1.1 en 295 utf-8
 AAR
 AARs
 ABI
@@ -18,6 +18,7 @@ CODEOWNERS
 Cartfile
 CircleCI
 Ciufo
+Codebase
 DNS
 DOM
 Datetime

docs/dev/SUMMARY.md

@@ -11,8 +11,8 @@
     - [Setup Build Environment](android/setup-android-build-environment.md)
     - [Android SDK/NDK versions](android/sdk-ndk-versions.md)
     - [Logging](android/logging.md)
-    - [Development with android-components](android/development-with-android-components.md)
-    - [Locally-published components in Fenix](android/locally-published-components-in-fenix.md)
+    - [Development with mozilla-central](android/development-with-mozilla-central.md)
+    - [Replacing the Glean Gradle plugin in mozilla-central](android/gradle-plugin-in-mc.md)
     - [Substituting glean_parser](android/glean-parser-substitution.md)
 - [iOS bindings](ios/index.md)
     - [Setup Build Environment](ios/setup-ios-build-environment.md)

docs/dev/android/development-with-mozilla-central.md

@@ -0,0 +1,52 @@
+# Working on unreleased Glean code in mozilla-central
+
+> **Note**: This guide is for mozilla-central Android builds. If you only need to replace the Glean Rust parts, refer to [Developing with a local Glean build](https://firefox-source-docs.mozilla.org/toolkit/components/glean/dev/local_glean.html) in the Firefox Source Docs.
+
+> **Note**: This guide only refers to building Fenix. It should work similarly for Focus Android.
+
+## Preparation
+
+This guide assumes you are already setup to build the mozilla-central repository for Android.
+Refer to [Getting Set Up To Work On The Firefox Codebase](https://firefox-source-docs.mozilla.org/setup/index.html) for more.
+
+Clone the Glean SDK repositories:
+
+```sh
+git clone https://github.com/mozilla/glean
+```
+
+## Cargo build targets
+
+By default when building Fenix using gradle, the rust-android plugin will compile Glean for every possible platform,
+which might end up in build failures.
+You can customize which targets are built in `glean/local.properties`
+([more information](https://github.com/ncalexan/rust-android-gradle/blob/HEAD/README.md#specifying-local-targets)):
+
+```
+# For physical devices:
+rust.targets=arm
+
+# For unit tests:
+# rust.targets=darwin # Or linux-*, windows-* (* = x86/x64)
+
+# For emulator only:
+rust.targets=x86
+```
+
+## Substituting projects
+
+Fenix has custom build logic for dealing with composite builds,
+so you should be able to configure it by simply adding the path to the Glean repository in the correct `local.properties` file:
+
+In `mozilla-central/mobile/android/fenix/local.properties`:
+
+```groovy
+autoPublish.glean.dir=../../../../glean
+```
+
+Make sure to use the correct path pointing to your Glean checkout.
+
+> **Note**: This substitution-based approach will not work for testing updates to the Glean Gradle plugin or `glean_parser` as shipped in the Glean Gradle Plugin.
+>
+> See [Replacing the Glean Gradle plugin in mozilla-central](gradle-plugin-in-mc.md).  
+> For replacing `glean_parser` in a local build, see [Substituting `glean_parser`](glean-parser-substitution.md).

docs/dev/android/gradle-plugin-in-mc.md

@@ -0,0 +1,35 @@
+# Replacing the Glean Gradle plugin in mozilla-central
+
+> **Note**: If you only need to replace the `glean_parser` Python parts used in the build see [Substituting `glean_parser`](glean-parser-substitution.md).
+> The approached documented in this chapter is only necessary if you changed `GleanGradlePlugin.groovy`.
+
+If you need to replace the Glean Gradle Plugin used by any component in mozilla-central, follow these steps:
+
+1. In your Glean repository increment the version number in `.buildconfig.yml` to something unused:
+
+   ```yaml
+   libraryVersion: 70.0.0
+   ```
+
+1. Build the Glean Gradle plugin and publish the plugin locally:
+
+   ```
+   ./gradlew glean-gradle-plugin:publishToMavenLocal
+   ```
+
+1. In your `mozilla-central` checkout, add the following line in `mobile/android/fenix/settings.gradle` file in the `pluginManagement` block:
+
+   ```gradle
+   mavenLocal()
+   ```
+
+1. Use the new version number where the plugin is imported in `mobile/android/fenix/build.gradle`:
+
+   ```
+   classpath "org.mozilla.telemetry:glean-gradle-plugin:70.0.0"
+   ```
+
+   This might need to be applied to the top-level `build.gradle` and other `build.gradle` files under `mobile/android` to apply to all components.
+
+
+Building Fenix will now use your locally published Glean Gradle Plugin.