Keep Gradle native-platform extraction markers (MOB-468)

CHANGELOG.md

@@ -1,3 +1,17 @@
+## [Unreleased]
+
+### Fixed
+
+- **Android deploys no longer crash concurrent Gradle builds (MOB-468).**
+  Before every `assembleDebug`, mob_dev deleted `~/.gradle/native/**/*.lock`
+  as "stale locks". native-platform holds those only while it extracts (they
+  are never left stale), and their content marks a finished extraction: without one, the next Gradle JVM rewrites
+  `libnative-platform.so` in place, over the inode every running Gradle JVM
+  (another project's build, a `--no-daemon` wrapper and its daemon) has
+  mapped, and those JVMs die with SIGSEGV (`ld-linux-x86-64.so.2+0x10f2` in
+  the wrapper, a JNI `stat`/`getPid` in the daemon). The markers are kept now;
+  the wrapper, daemon-registry and cache locks are still cleared.
+
 ## [0.7.22] - 2026-10-09
 
 ### Fixed

lib/mob_dev/native_build.ex

@@ -1574,15 +1574,22 @@ defmodule MobDev.NativeBuild do
   # Remove stale Gradle lock files left behind when a build is interrupted
   # (Ctrl+C, kill, etc.). These cause the next run to hang indefinitely while
   # the wrapper waits to acquire the lock.
-  defp clear_stale_gradle_locks do
-    gradle_home =
-      System.get_env("GRADLE_USER_HOME") ||
-        Path.join(System.user_home!(), ".gradle")
-
+  #
+  # Never `<gradle_home>/native/**/*.lock` (MOB-468): native-platform holds
+  # each only while it extracts (never left stale), and its 1-byte content
+  # marks a finished extraction. Without one, the next Gradle JVM re-extracts
+  # `libnative-platform.so` (and friends) in place, over the inode every
+  # running Gradle JVM has mapped, and those JVMs SIGSEGV (the wrapper in
+  # `ld-linux` at exit, the daemon in a JNI `stat`/`getPid`).
+  @doc false
+  @spec clear_stale_gradle_locks(Path.t()) :: :ok
+  def clear_stale_gradle_locks(
+        gradle_home \\ System.get_env("GRADLE_USER_HOME") ||
+          Path.join(System.user_home!(), ".gradle")
+      ) do
     patterns = [
       "#{gradle_home}/daemon/*/registry.bin.lock",
       "#{gradle_home}/wrapper/dists/**/*.lck",
-      "#{gradle_home}/native/**/*.lock",
       "#{gradle_home}/caches/**/*.lock",
       "#{gradle_home}/caches/**/*.lck"
     ]

test/mob_dev/native_build_test.exs

@@ -2400,6 +2400,34 @@ defmodule MobDev.NativeBuildTest do
     end
   end
 
+  describe "clear_stale_gradle_locks/1" do
+    @describetag :tmp_dir
+
+    # MOB-468: native-platform's `<lib>.so.lock` marks a finished extraction.
+    # Deleting it made the next Gradle JVM rewrite the mapped .so in place and
+    # crashed every concurrent Gradle JVM (SIGSEGV in ld-linux / JNI).
+    test "clears stale wrapper, daemon and cache locks but keeps native-platform's extraction markers",
+         %{tmp_dir: home} do
+      marker = Path.join(home, "native/68d5/linux-amd64/libnative-platform.so.lock")
+      lib = Path.join(home, "native/68d5/linux-amd64/libnative-platform.so")
+
+      stale = [
+        Path.join(home, "daemon/8.2.1/registry.bin.lock"),
+        Path.join(home, "caches/8.2.1/fileHashes/fileHashes.lock")
+      ]
+
+      for f <- [marker, lib | stale] do
+        File.mkdir_p!(Path.dirname(f))
+        File.write!(f, <<1>>)
+      end
+
+      assert NativeBuild.clear_stale_gradle_locks(home) == :ok
+      assert File.exists?(marker)
+      assert File.exists?(lib)
+      for f <- stale, do: refute(File.exists?(f), f)
+    end
+  end
+
   # ── ios_bundle_id/1 ───────────────────────────────────────────────────────────
   #
   # The sim bundle, the device bundle, and code signing must all stamp the