Fix handling of bytecode files

packages/pytest/meta.yaml

@@ -8,12 +8,13 @@ source:
 
   patches:
     - patches/named-tmp-and-rm-dup2.patch
+    - patches/workaround_get_tag.patch
 
 requirements:
   run:
     - atomicwrites
     - attrs
-    - more-itertools 
+    - more-itertools
     - pluggy
     - py
     - setuptools

packages/pytest/patches/workaround_get_tag.patch

+diff -ur pytest-3.6.3-bak/src/_pytest/assertion/rewrite.py pytest-3.6.3/src/_pytest/assertion/rewrite.py
+--- pytest-3.6.3-bak/src/_pytest/assertion/rewrite.py	2018-11-08 14:58:43.984236991 -0500
++++ pytest-3.6.3/src/_pytest/assertion/rewrite.py	2018-11-08 14:59:59.881455735 -0500
+@@ -19,7 +19,7 @@
+ 
+ 
+ # pytest caches rewritten pycs in __pycache__.
+-if hasattr(imp, "get_tag"):
++if hasattr(imp, "get_tag") and imp.get_tag() is not None:
+     PYTEST_TAG = imp.get_tag() + "-PYTEST"
+ else:
+     if hasattr(sys, "pypy_version_info"):

pyodide_build/buildpkg.py

@@ -133,7 +133,7 @@ def package_files(buildpath, srcpath, pkg, args):
         '--js-output={}'.format(name + '.js'),
         '--export-name=pyodide._module',
         '--exclude', '*.wasm.pre',
-        '--exclude', '__pycache__',
+        '--exclude', '*__pycache__*',
         '--use-preload-plugins'],
         cwd=buildpath, check=True)
     subprocess.run([

src/main.c

@@ -41,11 +41,40 @@ main(int argc, char** argv)
 {
   hiwire_setup();
 
-  setenv("PYTHONDONTWRITEBYTECODE", "1", 0);
   setenv("PYTHONHOME", "/", 0);
 
   Py_InitializeEx(0);
 
+  // This doesn't seem to work anymore, but I'm keeping it for good measure anyway
+  // The effective way to turn this off is below: setting sys.done_write_bytecode = True
+  setenv("PYTHONDONTWRITEBYTECODE", "1", 0);
+
+  PyObject* sys = PyImport_ImportModule("sys");
+  if (sys == NULL) {
+    return 1;
+  }
+  if (PyObject_SetAttrString(sys, "dont_write_bytecode", Py_True)) {
+    Py_DECREF(sys);
+    return 1;
+  }
+
+  // By disabling the cache_tag, Python won't look for cached bytecode files when
+  // importing modules, which saves on filesystem I/O time
+  PyObject *implementation = PyObject_GetAttrString(sys, "implementation");
+  if (implementation == NULL) {
+    Py_DECREF(sys);
+    return 1;
+  }
+
+  if (PyObject_SetAttrString(implementation, "cache_tag", Py_None)) {
+    Py_DECREF(implementation);
+    Py_DECREF(sys);
+    return 1;
+  }
+
+  Py_DECREF(implementation);
+  Py_DECREF(sys);
+
   if (js2python_init() || JsImport_init() || JsProxy_init() ||
       pyimport_init() || pyproxy_init() || python2js_init() ||
       runpython_init_js() || runpython_init_py() || runpython_finalize_js()) {

test/test_common.py

@@ -49,10 +49,42 @@ def test_import(name, selenium_standalone):
                 '{} fails to load and is not supported on {}.'
                 .format(name, selenium_standalone.browser))
 
+    selenium_standalone.run("import glob, os")
+
+    baseline_pyc = selenium_standalone.run(
+        """
+        len(list(glob.glob(
+            '/lib/python3.7/site-packages/**/*.pyc',
+            recursive=True)
+        ))
+        """
+    )
+
+    selenium_standalone.load_package(name)
+
+    # Make sure there are no additional .pyc file
+    assert selenium_standalone.run(
+        """
+        len(list(glob.glob(
+            '/lib/python3.7/site-packages/**/*.pyc',
+            recursive=True)
+        ))
+        """
+    ) == baseline_pyc
+
     for import_name in meta.get('test', {}).get('imports', []):
-        selenium_standalone.load_package(name)
         try:
             selenium_standalone.run('import %s' % import_name)
         except Exception as e:
             print(selenium_standalone.logs)
             raise
+
+        # Make sure that even after importing, there are no additional .pyc files
+        assert selenium_standalone.run(
+            """
+            len(list(glob.glob(
+                '/lib/python3.7/site-packages/**/*.pyc',
+                recursive=True)
+            ))
+            """
+        ) == baseline_pyc