Add file_packager tests and changelog mention

Author: lkwinta

ChangeLog.md

@@ -34,6 +34,8 @@ See docs/process.md for more on how version tagging works.
 - emcc will now error if `MINIMAL_RUNTIME_STREAMING_WASM_COMPILATION` or
   `MINIMAL_RUNTIME_STREAMING_WASM_INSTANTIATION` are used with `SINGLE_FILE`.
   These are fundamentally incompatible but were previously ignored. (#24849)
+- `--modularize` flag was added to `file_packager.py` available when run 
+  standalone, to enable ES6 imports of generated JavaScript code
 
 4.0.12 - 08/01/25
 -----------------

test/test_other.py

@@ -3804,21 +3804,34 @@ def check(text):
     stderr = self.expect_fail([FILE_PACKAGER, 'test.data', '--quiet', '--preload', '../data1.txt'])
     self.assertContained('which is not contained within the current directory', stderr)
 
+    stderr = self.expect_fail([FILE_PACKAGER, 'test.data', '--quiet', '--preload', '../data1.txt', '--modularize'])
+    self.assertContained('which is not contained within the current directory', stderr)
+
     # relative path that ends up under us is cool
     proc = self.run_process([FILE_PACKAGER, 'test.data', '--quiet', '--preload', '../subdir/data2.txt'], stderr=PIPE, stdout=PIPE)
     self.assertEqual(proc.stderr, '')
     check(proc.stdout)
 
-    # direct path leads to the same code being generated - relative path does not make us do anything different
-    proc2 = self.run_process([FILE_PACKAGER, 'test.data', '--quiet', '--preload', 'data2.txt'], stderr=PIPE, stdout=PIPE)
-    check(proc2.stdout)
-    self.assertEqual(proc2.stderr, '')
+    proc = self.run_process([FILE_PACKAGER, 'test.data', '--quiet', '--preload', '../subdir/data2.txt', '--modularize'], stderr=PIPE, stdout=PIPE)
+    self.assertEqual(proc.stderr, '')
+    check(proc.stdout)
 
     def clean(txt):
       lines = txt.splitlines()
       lines = [l for l in lines if 'PACKAGE_UUID' not in l and 'loadPackage({' not in l]
       return ''.join(lines)
 
+    # direct path leads to the same code being generated - relative path does not make us do anything different
+    proc2 = self.run_process([FILE_PACKAGER, 'test.data', '--quiet', '--preload', 'data2.txt'], stderr=PIPE, stdout=PIPE)
+    check(proc2.stdout)
+    self.assertEqual(proc2.stderr, '')
+
+    self.assertTextDataIdentical(clean(proc.stdout), clean(proc2.stdout))
+
+    proc2 = self.run_process([FILE_PACKAGER, 'test.data', '--quiet', '--preload', 'data2.txt', '--modularize'], stderr=PIPE, stdout=PIPE)
+    check(proc2.stdout)
+    self.assertEqual(proc2.stderr, '')
+
     self.assertTextDataIdentical(clean(proc.stdout), clean(proc2.stdout))
 
   def test_file_packager_response_file(self):
@@ -3919,6 +3932,11 @@ def test_file_packager_returns_error_if_target_equal_to_jsoutput(self):
     err = self.expect_fail([FILE_PACKAGER, 'test.data', '--js-output=test.data'])
     self.assertContained(MESSAGE, err)
 
+  def test_file_packager_returns_error_if_emcc_and_modularize(self):
+    MESSAGE = 'error: Can\'t use modularize option together with --from-emcc since the code should be embedded within emcc\'s code'
+    err = self.expect_fail([FILE_PACKAGER, 'test.data', '--modularize', '--from-emcc'])
+    self.assertEqual(MESSAGE, err)
+
   def test_file_packager_embed(self):
     create_file('data.txt', 'hello data')
 
@@ -3945,6 +3963,21 @@ def test_file_packager_embed(self):
     output = self.run_js('a.out.js')
     self.assertContained('hello data', output)
 
+  def test_filepackager_standalone_modularize(self):
+    MESSAGE = 'Remember to build the main file with `-sFORCE_FILESYSTEM` so that it includes support for loading this file package'
+
+    create_file('data.txt', 'hello data')
+    err = self.run_process([FILE_PACKAGER, 'test.data', '--modularize', '--preload', 'data.txt', '--js-output=data.js'], stderr=PIPE).stderr
+    self.assertEqual(MESSAGE, err)
+
+    generated_content = read_file('data.js')
+
+    expected_opening = "export default function loadDataFile(Module) {"
+    expected_closing = "\n};\n// END the loadDataFile function"
+
+    self.assertContained(expected_opening, generated_content)
+    self.assertContained(expected_closing, generated_content)
+
   @crossplatform
   def test_file_packager_depfile(self):
     create_file('data1.txt', 'data1')

tools/file_packager.py

@@ -492,7 +492,7 @@ def main():  # noqa: C901, PLR0912, PLR0915
     return 1
 
   if options.from_emcc and options.modularize:
-    diagnostics.error('Can\'t use modularize option together with --from-emcc since the code should be embedded'
+    diagnostics.error('Can\'t use modularize option together with --from-emcc since the code should be embedded '
         'within emcc\'s code')
     return 1