Always output a tarball from cc_binary to simplify logic. (#936)

* Always output a tarball from cc_binary to simplify logic. This will change the result of --config=wasm builds that were previously outputting a single file.

* better to use early return here

* Always output a tarball from cc_binary to simplify logic. This will change the result of --config=wasm builds that were previously outputting a single file.

* better to use early return here

Co-authored-by: Mitch Foley <mitchfoley@chromium.org>

bazel/emscripten_toolchain/link_wrapper.py

@@ -153,17 +153,14 @@
         wasm_base,
         '--add-section=external_debug_info=debugsection.tmp'])
 
-# If we have more than one output file then create tarball
-if len(files) > 1:
-  cmd = ['tar', 'cf', 'tmp.tar'] + files
-  subprocess.check_call(cmd, cwd=outdir)
-  os.rename(os.path.join(outdir, 'tmp.tar'), output_file)
-elif len(files) == 1:
-  # Otherwise, if only have a single output than move it to the expected name
-  if files[0] != os.path.basename(output_file):
-    os.rename(os.path.join(outdir, files[0]), output_file)
-else:
+# Make sure we have at least one output file.
+if not len(files):
   print('emcc.py did not appear to output any known files!')
   sys.exit(1)
 
+# cc_binary must output exactly one file; put all the output files in a tarball.
+cmd = ['tar', 'cf', 'tmp.tar'] + files
+subprocess.check_call(cmd, cwd=outdir)
+os.rename(os.path.join(outdir, 'tmp.tar'), output_file)
+
 sys.exit(0)

bazel/emscripten_toolchain/wasm_binary.py

@@ -21,7 +21,6 @@
 import argparse
 import os
 import subprocess
-import sys
 
 
 def ensure(f):
@@ -44,26 +43,9 @@ def main():
   basename = os.path.basename(args.archive)
   stem = basename.split('.')[0]
 
-  # Check the type of the input file
-  mimetype_bytes = subprocess.check_output(['file', '-Lb', '--mime-type', '--mime-encoding', args.archive])
-  mimetype = mimetype_bytes.decode(sys.stdout.encoding)
-
-  # If we have a tar, extract all files. If we have just a single file, copy it.
-  if 'tar' in mimetype:
-    subprocess.check_call(
-        ['tar', 'xf', args.archive, '-C', args.output_path])
-  elif 'binary' in mimetype:
-    subprocess.check_call([
-        'cp',
-        args.archive,
-        os.path.join(args.output_path, stem + '.wasm')])
-  elif 'text' in mimetype:
-    subprocess.check_call([
-        'cp',
-        args.archive,
-        os.path.join(args.output_path, stem + '.js')])
-  else:
-    subprocess.check_call(['cp', args.archive, args.output_path])
+  # Extract all files from the tarball.
+  subprocess.check_call(
+      ['tar', 'xf', args.archive, '-C', args.output_path])
 
   # At least one of these two files should exist at this point.
   ensure(os.path.join(args.output_path, stem + '.js'))