[Infra] Annotate subprojects with the type of project

We extended the format of `subprojects.cfg` to support inline
comments. Then, added a comment to indicate what type of project each
entry points to, e.g. SDK or test-only. This is useful for tooling,
like Gemini, as it can now understand better which subprojects to
read/modify if a global, SDK-specific, action is necessary.

The `agents.md` doc has been updated accordingly.

Author: rlazo

agents.md

@@ -2,6 +2,19 @@
 
 This guide provides essential information for working within the `firebase-android-sdk` repository.
 
+## Project Structure
+
+The `subprojects.cfg` file lists all the subprojects in this repository. Each line in this file
+follows the format `<project-path> # <project-type>`, where `project-type` can be one of the
+following:
+
+- `sdk`: A public-facing SDK that is published.
+- `test`: A test application or a test-only module.
+- `util`: A utility module that is not part of the public API.
+- `directory`: A directory containing other subprojects.
+
+This file is useful for understanding the role of each subproject in the repository.
+
 ## Environment Setup
 
 To work with this repository, the Android SDK must be installed. Use the `sdkmanager` command-line

settings.gradle.kts

@@ -46,14 +46,14 @@ dependencyResolutionManagement {
  *
  * Expected file format:
  * - Empty lines are ignored.
- * - Lines starting with # are considered comments.
+ * - Text following a '#' character on the same line is treated as a comment.
  * - Other lines are treated as project paths.
  */
 fun discoverSubprojects(subprojectsFile: File): List<String> {
   return subprojectsFile
     .readLines()
-    .map { it.trim() }
-    .filter { it.isNotEmpty() && !it.startsWith("#") }
+    .map { it.split("#").firstOrNull()?.trim() ?: "" }
+    .filter { it.isNotEmpty() }
 }
 
 /**

subprojects.cfg

@@ -1,71 +1,71 @@
-appcheck
-appcheck:firebase-appcheck-debug-testing
-appcheck:firebase-appcheck-debug
-appcheck:firebase-appcheck-interop
-appcheck:firebase-appcheck-playintegrity
-appcheck:firebase-appcheck-recaptchaenterprise
-appcheck:firebase-appcheck
+appcheck # directory
+appcheck:firebase-appcheck-debug-testing # sdk
+appcheck:firebase-appcheck-debug # sdk
+appcheck:firebase-appcheck-interop # sdk
+appcheck:firebase-appcheck-playintegrity # sdk
+appcheck:firebase-appcheck-recaptchaenterprise # sdk
+appcheck:firebase-appcheck # sdk
 
-firebase-abt
-firebase-ai
-firebase-annotations
-firebase-appdistribution
-firebase-appdistribution-api
-firebase-common
-firebase-common:data-collection-tests
-firebase-components
-firebase-components:firebase-dynamic-module-support
-firebase-config
-firebase-config:bandwagoner
-firebase-config:test-app
-firebase-config-interop
-firebase-crashlytics
-firebase-crashlytics-ndk
-firebase-database
-firebase-database-collection
-firebase-dataconnect
-firebase-dataconnect:androidTestutil
-firebase-dataconnect:connectors
-firebase-dataconnect:testutil
-firebase-datatransport
-firebase-firestore
-firebase-functions
-firebase-messaging
-firebase-messaging-directboot
-firebase-inappmessaging
-firebase-inappmessaging-display
-firebase-installations-interop
-firebase-installations
-firebase-ml-modeldownloader
-firebase-ml-modeldownloader:ml-data-collection-tests
-firebase-perf
-firebase-perf:dev-app
-firebase-perf:e2e-app
-firebase-sessions
-firebase-sessions:benchmark
-firebase-sessions:test-app
-firebase-storage
-protolite-well-known-types
+firebase-abt # sdk
+firebase-ai # sdk
+firebase-annotations # sdk
+firebase-appdistribution # sdk
+firebase-appdistribution-api # sdk
+firebase-common # sdk
+firebase-common:data-collection-tests # tests
+firebase-components # sdk
+firebase-components:firebase-dynamic-module-support # sdk
+firebase-config # sdk
+firebase-config:bandwagoner # test
+firebase-config:test-app # test
+firebase-config-interop # sdk
+firebase-crashlytics # sdk
+firebase-crashlytics-ndk # sdk
+firebase-database # sdk
+firebase-database-collection # sdk
+firebase-dataconnect # sdk
+firebase-dataconnect:androidTestutil # util
+firebase-dataconnect:connectors # sdk
+firebase-dataconnect:testutil # util
+firebase-datatransport # sdk
+firebase-firestore # sdk
+firebase-functions # sdk
+firebase-messaging # sdk
+firebase-messaging-directboot # sdk
+firebase-inappmessaging # sdk
+firebase-inappmessaging-display # sdk
+firebase-installations-interop # sdk
+firebase-installations # sdk
+firebase-ml-modeldownloader # sdk
+firebase-ml-modeldownloader:ml-data-collection-tests # test
+firebase-perf # sdk
+firebase-perf:dev-app # test
+firebase-perf:e2e-app # test
+firebase-sessions # sdk
+firebase-sessions:benchmark # util
+firebase-sessions:test-app # test
+firebase-storage # sdk
+protolite-well-known-types # sdk
 
-encoders
-encoders:firebase-encoders
-encoders:firebase-encoders-json
-encoders:firebase-encoders-processor
-encoders:firebase-encoders-proto
-encoders:firebase-encoders-reflective
-encoders:firebase-decoders-json
-encoders:protoc-gen-firebase-encoders
-encoders:protoc-gen-firebase-encoders:tests
+encoders # directory
+encoders:firebase-encoders # sdk
+encoders:firebase-encoders-json # sdk
+encoders:firebase-encoders-processor # sdk
+encoders:firebase-encoders-proto # sdk
+encoders:firebase-encoders-reflective # sdk
+encoders:firebase-decoders-json # sdk
+encoders:protoc-gen-firebase-encoders # sdk
+encoders:protoc-gen-firebase-encoders:tests # test
 
-integ-testing
+integ-testing # util
 
-tools:lint
+tools:lint # util
 
-transport
-transport:transport-api
-transport:transport-backend-cct
-transport:transport-runtime
-transport:transport-runtime-testing
+transport # directory
+transport:transport-api # sdk
+transport:transport-backend-cct # sdk
+transport:transport-runtime # sdk
+transport:transport-runtime-testing # sdk
 
 # Test Apps
 # disabled since they require google-services.json to build which is not always available in CI.