Cleanup file_packager python code (emscripten-core#10177)

Also clean up the test code (test change should be NFC).

tests/test_other.py

@@ -8,7 +8,6 @@
 
 from __future__ import print_function
 from functools import wraps
-import filecmp
 import glob
 import itertools
 import json
@@ -2543,21 +2542,26 @@ def test_file_packager(self):
     self.assertNotContained('below the current directory', proc2.stderr)
 
     def clean(txt):
-      return [line for line in txt.split('\n') if 'PACKAGE_UUID' not in line and 'loadPackage({' not in line]
+      lines = txt.splitlines()
+      lines = [l for l in lines if 'PACKAGE_UUID' not in l and 'loadPackage({' not in l]
+      return ''.join(lines)
 
-    assert clean(proc.stdout) == clean(proc2.stdout)
+    self.assertTextDataIdentical(clean(proc.stdout), clean(proc2.stdout))
 
     # verify '--separate-metadata' option produces separate metadata file
     os.chdir('..')
 
     run_process([PYTHON, FILE_PACKAGER, 'test.data', '--preload', 'data1.txt', '--preload', 'subdir/data2.txt', '--js-output=immutable.js', '--separate-metadata'])
-    assert os.path.isfile('immutable.js.metadata')
-    # verify js output file is immutable when metadata is separated
+    self.assertExists('immutable.js.metadata')
+    # verify js output JS file is not touched when the metadata is separated
     shutil.copy2('immutable.js', 'immutable.js.copy') # copy with timestamp preserved
+    # ensure some time passes before running the packager again so that if it does touch the
+    # js file it will end up with the different timestamp.
+    time.sleep(1.0)
     run_process([PYTHON, FILE_PACKAGER, 'test.data', '--preload', 'data1.txt', '--preload', 'subdir/data2.txt', '--js-output=immutable.js', '--separate-metadata'])
-    assert filecmp.cmp('immutable.js.copy', 'immutable.js')
     # assert both file content and timestamp are the same as reference copy
-    self.assertEqual(str(os.path.getmtime('immutable.js.copy')), str(os.path.getmtime('immutable.js')))
+    self.assertTextDataIdentical(open('immutable.js.copy').read(), open('immutable.js').read())
+    self.assertEqual(os.path.getmtime('immutable.js.copy'), os.path.getmtime('immutable.js'))
     # verify the content of metadata file is correct
     with open('immutable.js.metadata') as f:
       metadata = json.load(f)

tools/file_packager.py

@@ -232,7 +232,8 @@ def main():
       from_emcc = True
       leading = ''
     elif arg.startswith('--plugin'):
-      plugin = open(arg.split('=', 1)[1], 'r').read()
+      with open(arg.split('=', 1)[1]) as f:
+        plugin = f.read()
       eval(plugin) # should append itself to plugins
       leading = ''
     elif leading == 'preload' or leading == 'embed':
@@ -391,17 +392,18 @@ def was_seen(name):
   if has_preloaded:
     # Bundle all datafiles into one archive. Avoids doing lots of simultaneous
     # XHRs which has overhead.
-    data = open(data_target, 'wb')
     start = 0
-    for file_ in data_files:
-      file_['data_start'] = start
-      curr = open(file_['srcpath'], 'rb').read()
-      file_['data_end'] = start + len(curr)
-      if AV_WORKAROUND:
-          curr += '\x00'
-      start += len(curr)
-      data.write(curr)
-    data.close()
+    with open(data_target, 'wb') as data:
+      for file_ in data_files:
+        file_['data_start'] = start
+        with open(file_['srcpath'], 'rb') as f:
+          curr = f.read()
+        file_['data_end'] = start + len(curr)
+        if AV_WORKAROUND:
+            curr += '\x00'
+        start += len(curr)
+        data.write(curr)
+
     # TODO: sha256sum on data_target
     if start > 256 * 1024 * 1024:
       print('warning: file packager is creating an asset bundle of %d MB. '
@@ -913,20 +915,17 @@ def was_seen(name):
       # differs from the current generated one, otherwise leave the file
       # untouched preserving its old timestamp
       if os.path.isfile(jsoutput):
-        f = open(jsoutput, 'r+')
-        old = f.read()
+        with open(jsoutput) as f:
+          old = f.read()
         if old != ret:
-          f.seek(0)
-          f.write(ret)
-          f.truncate()
+          with open(jsoutput, 'w') as f:
+            f.write(ret)
       else:
-        f = open(jsoutput, 'w')
-        f.write(ret)
-      f.close()
+        with open(jsoutput, 'w') as f:
+          f.write(ret)
       if separate_metadata:
-        f = open(jsoutput + '.metadata', 'w')
-        json.dump(metadata, f, separators=(',', ':'))
-        f.close()
+        with open(jsoutput + '.metadata', 'w') as f:
+          json.dump(metadata, f, separators=(',', ':'))
 
   return 0