Disallow files additional named GeneratedPluginRegistrant.java.

ci/builders/linux_unopt.json

@@ -40,6 +40,10 @@
                     "name": "test:format_and_dart_test",
                     "script": "flutter/ci/format.sh"
                 },
+                {
+                    "nane": "test:GeneratedPluginRegistant.java omitted",
+                    "script": "flutter/ci/test/format_no_generated_java_test.sh"
+                },
                 {
                     "language": "python3",
                     "name": "test: Host_Tests_for_host_debug_unopt",

ci/format.sh

@@ -32,6 +32,29 @@ SRC_DIR="$(cd "$SCRIPT_DIR/../.."; pwd -P)"
 DART_SDK_DIR="${SRC_DIR}/third_party/dart/tools/sdks/dart-sdk"
 DART="${DART_SDK_DIR}/bin/dart"
 
+# Check if a file named **/GeneratedPluginRegistrant.java exists in the project.
+# If it does, fail the build and print a message to the user pointing them to
+# the file and instructing them to remove it.
+#
+# See: https://github.com/flutter/flutter/issues/143782.
+
+# The expected path to the file. Any *other* path is unexpected.
+EXPECTED_PATHS=("./shell/platform/android/test/io/flutter/plugins/GeneratedPluginRegistrant.java")
+
+# Find all files named GeneratedPluginRegistrant.java in the project.
+GENERATED_PLUGIN_REGISTRANT_PATHS=$(find "$SRC_DIR/flutter" -name "GeneratedPluginRegistrant.java")
+
+# Check for GeneratedPluginRegistrant.java in unexpected locations
+for expected_path in "${EXPECTED_PATHS[@]}"; do
+    found_files=$(find . -name "GeneratedPluginRegistrant.java" -not -path "$expected_path")
+
+    for file in $found_files; do
+        echo "Error: Unexpected GeneratedPluginRegistrant.java found: $file"
+        echo "Please remove the unexpected file and see: https://github.com/flutter/flutter/issues/143782"
+        exit 1
+    done
+done
+
 cd "$SCRIPT_DIR"
 "$DART" \
   --disable-dart-dev \

ci/test/format_no_generated_java_test.sh

@@ -0,0 +1,58 @@
+#!/bin/bash
+#
+# Copyright 2013 The Flutter Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+set -e
+
+# Needed because if it is set, cd may print the path it changed to.
+unset CDPATH
+
+# On Mac OS, readlink -f doesn't work, so follow_links traverses the path one
+# link at a time, and then cds into the link destination and find out where it
+# ends up.
+#
+# The function is enclosed in a subshell to avoid changing the working directory
+# of the caller.
+function follow_links() (
+  cd -P "$(dirname -- "$1")"
+  file="$PWD/$(basename -- "$1")"
+  while [[ -h "$file" ]]; do
+    cd -P "$(dirname -- "$file")"
+    file="$(readlink -- "$file")"
+    cd -P "$(dirname -- "$file")"
+    file="$PWD/$(basename -- "$file")"
+  done
+  echo "$file"
+)
+
+SCRIPT_DIR=$(follow_links "$(dirname -- "${BASH_SOURCE[0]}")")
+SRC_DIR="$(
+  cd "$SCRIPT_DIR/../../.."
+  pwd -P
+)"
+FLUTTER_DIR="$SRC_DIR/flutter"
+
+# Creates a file named `GeneratedPluginRegistrant.java` in the project outside
+# of it's expected location in shell/platform/android/test/... (where the exact
+# name and location is required to get loaded).
+#
+# This file is typically generated by Flutter tooling and should not exist.
+touch "$FLUTTER_DIR/GeneratedPluginRegistrant.java"
+
+# Create a trap that, on exit, removes the file.
+function cleanup() {
+  rm -f "$FLUTTER_DIR/GeneratedPluginRegistrant.java"
+}
+trap cleanup EXIT
+
+# Runs ../format.sh and verifies that it fails with the expected error message.
+# If it fails, the script prints an error message and exits with a non-zero status.
+"$FLUTTER_DIR/ci/format.sh" || {
+  echo "PASS: analyze.sh failed as expected"
+  exit 0
+}
+
+echo "FAIL: format.sh did not fail as expected"
+exit 1