[Feature]: Config-driven Android signing without regenerating gen/android in CI

[thwbh]

Category

New Feature

Target Platform

Android

Feature Description

Add config-driven Android signing so the keystore/signing setup no longer requires hand-editing the generated gen/android/app/build.gradle.kts or running a separate template-application script in CI.

Today the Android signing config lives only in the Tauri-generated Gradle file. Because gen/ is gitignored by default, CI must run cargo tauri android init, which regenerates a stock build.gradle.kts without our signing config — so we re-apply it via src-tauri/android-templates/setup-android.sh and generate keystore.properties from CI env vars. This is brittle: init aborts/overwrites against an existing gen/android, and every regeneration risks losing customizations.

Proposed Solution / Mockup

Two complementary tracks (this issue tracks our own repo's adoption; the upstream piece is noted under Alternatives):

1. Commit gen/android and read signing from env vars in a committed build.gradle.kts.

Un-gitignore gen/android (keeping its nested artifact .gitignores), commit a signing-aware build.gradle.kts, and have CI just set env vars + run tauri android build — no init, no setup-android.sh:

signingConfigs {
    create("release") {
        System.getenv("KEYSTORE_FILE")?.let {
            storeFile = file(it)
            storePassword = System.getenv("KEYSTORE_PASSWORD")
            keyAlias = System.getenv("KEY_ALIAS")
            keyPassword = System.getenv("KEY_PASSWORD")
        }
    }
}

Outcome: CI checks out the repo (project already present) and runs the build. The only dynamic step left is decoding the keystore secret to a file + exporting env vars — intrinsic to signing, not project glue. Keystore file and passwords stay out of git.

2. (Stretch) Drop the init call from the CD workflow once gen/android is committed, and reduce setup-android.sh to nothing (or the keystore-from-secret decode only).

Problem Statement (Optional)

The current signing flow is the most fragile part of the Android build. cargo tauri android init is required in CD only because gen/ is gitignored; that forces regeneration, which wipes signing config and fights any existing gen/android folder. This has caused repeated CD breakage.

Alternatives Considered (Optional)

• Upstream contribution: add an android.signing block to tauri.conf.json that the Tauri CLI wires into Gradle signingConfigs. This removes the manual Gradle edit for everyone, but must be a PR to tauri-apps/tauri (the CLI owns config parsing + Gradle codegen) — not something we can ship as a standalone crate. Worth floating upstream as an RFC.
• Standalone shim crate: a cargo install-able pre-build tool that patches gen/android before the build. Rejected as the preferred path — it's the same category as the current shell script, just nicer; it productizes the workaround instead of removing it.
• tauri android init -f: still regenerates and loses customizations; not a fix.

Additional Context (Optional)

Relevant files: src-tauri/android-templates/setup-android.sh, src-tauri/gen/android/app/build.gradle.kts (generated), .github CD workflow. Tauri docs confirm gen/ is meant to be committable (Tauri discussion #8323), and that signing currently requires editing the generated build.gradle.kts (Tauri Android Code Signing docs).