Issue 4090 - Make require() load modules lazily

ensure_dependencies.py

Index: ensure_dependencies.py
===================================================================
--- a/ensure_dependencies.py
+++ b/ensure_dependencies.py
@@ -1,10 +1,9 @@
 #!/usr/bin/env python
-# coding: utf-8
 
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 import sys
 import os
 import posixpath
@@ -14,17 +13,17 @@ import errno
 import logging
 import subprocess
 import urlparse
 import argparse
 
 from collections import OrderedDict
 from ConfigParser import RawConfigParser
 
-USAGE = """
+USAGE = '''
 A dependencies file should look like this:
 
   # VCS-specific root URLs for the repositories
   _root = hg:https://hg.adblockplus.org/ git:https://github.com/adblockplus/
   # File to update this script from (optional)
   _self = buildtools/ensure_dependencies.py
   # Clone elemhidehelper repository into extensions/elemhidehelper directory at
   # tag "1.2".
@@ -33,192 +32,192 @@ A dependencies file should look like thi
   # revision IDs.
   buildtools = buildtools hg:016d16f7137b git:f3f8692f82e5
   # Clone the adblockplus repository into adblockplus directory, overwriting the
   # usual source URL for Git repository and specifying VCS specific revision IDs.
   adblockplus = adblockplus hg:893426c6a6ab git:git@github.com:user/adblockplus.git@b2ffd52b
   # Clone the adblockpluschrome repository into the adblockpluschrome directory,
   # from a specific Git repository, specifying the revision ID.
   adblockpluschrome = git:git@github.com:user/adblockpluschrome.git@1fad3a7
-"""
+'''
 
 SKIP_DEPENDENCY_UPDATES = os.environ.get(
-    "SKIP_DEPENDENCY_UPDATES", ""
-).lower() not in ("", "0", "false")
+    'SKIP_DEPENDENCY_UPDATES', ''
+).lower() not in ('', '0', 'false')
 
 
 class Mercurial():
     def istype(self, repodir):
-        return os.path.exists(os.path.join(repodir, ".hg"))
+        return os.path.exists(os.path.join(repodir, '.hg'))
 
     def clone(self, source, target):
-        if not source.endswith("/"):
-            source += "/"
-        subprocess.check_call(["hg", "clone", "--quiet", "--noupdate", source, target])
+        if not source.endswith('/'):
+            source += '/'
+        subprocess.check_call(['hg', 'clone', '--quiet', '--noupdate', source, target])
 
     def get_revision_id(self, repo, rev=None):
-        command = ["hg", "id", "--repository", repo, "--id"]
+        command = ['hg', 'id', '--repository', repo, '--id']
         if rev:
-            command.extend(["--rev", rev])
+            command.extend(['--rev', rev])
 
         # Ignore stderr output and return code here: if revision lookup failed we
         # should simply return an empty string.
         result = subprocess.Popen(command, stdout=subprocess.PIPE, stderr=subprocess.PIPE).communicate()[0]
         return result.strip()
 
     def pull(self, repo):
-        subprocess.check_call(["hg", "pull", "--repository", repo, "--quiet"])
+        subprocess.check_call(['hg', 'pull', '--repository', repo, '--quiet'])
 
     def update(self, repo, rev, revname):
-        subprocess.check_call(["hg", "update", "--repository", repo, "--quiet", "--check", "--rev", rev])
+        subprocess.check_call(['hg', 'update', '--repository', repo, '--quiet', '--check', '--rev', rev])
 
     def ignore(self, target, repo):
 
         if not self.istype(target):
 
-            config_path = os.path.join(repo, ".hg", "hgrc")
-            ignore_path = os.path.abspath(os.path.join(repo, ".hg", "dependencies"))
+            config_path = os.path.join(repo, '.hg', 'hgrc')
+            ignore_path = os.path.abspath(os.path.join(repo, '.hg', 'dependencies'))
 
             config = RawConfigParser()
             config.read(config_path)
 
-            if not config.has_section("ui"):
-                config.add_section("ui")
+            if not config.has_section('ui'):
+                config.add_section('ui')
 
-            config.set("ui", "ignore.dependencies", ignore_path)
-            with open(config_path, "w") as stream:
+            config.set('ui', 'ignore.dependencies', ignore_path)
+            with open(config_path, 'w') as stream:
                 config.write(stream)
 
             module = os.path.relpath(target, repo)
             _ensure_line_exists(ignore_path, module)
 
     def postprocess_url(self, url):
         return url
 
 
 class Git():
     def istype(self, repodir):
-        return os.path.exists(os.path.join(repodir, ".git"))
+        return os.path.exists(os.path.join(repodir, '.git'))
 
     def clone(self, source, target):
-        source = source.rstrip("/")
-        if not source.endswith(".git"):
-            source += ".git"
-        subprocess.check_call(["git", "clone", "--quiet", source, target])
+        source = source.rstrip('/')
+        if not source.endswith('.git'):
+            source += '.git'
+        subprocess.check_call(['git', 'clone', '--quiet', source, target])
 
-    def get_revision_id(self, repo, rev="HEAD"):
-        command = ["git", "rev-parse", "--revs-only", rev + '^{commit}']
+    def get_revision_id(self, repo, rev='HEAD'):
+        command = ['git', 'rev-parse', '--revs-only', rev + '^{commit}']
         return subprocess.check_output(command, cwd=repo).strip()
 
     def pull(self, repo):
         # Fetch tracked branches, new tags and the list of available remote branches
-        subprocess.check_call(["git", "fetch", "--quiet", "--all", "--tags"], cwd=repo)
+        subprocess.check_call(['git', 'fetch', '--quiet', '--all', '--tags'], cwd=repo)
         # Next we need to ensure all remote branches are tracked
         newly_tracked = False
-        remotes = subprocess.check_output(["git", "branch", "--remotes"], cwd=repo)
-        for match in re.finditer(r"^\s*(origin/(\S+))$", remotes, re.M):
+        remotes = subprocess.check_output(['git', 'branch', '--remotes'], cwd=repo)
+        for match in re.finditer(r'^\s*(origin/(\S+))$', remotes, re.M):
             remote, local = match.groups()
-            with open(os.devnull, "wb") as devnull:
-                if subprocess.call(["git", "branch", "--track", local, remote],
+            with open(os.devnull, 'wb') as devnull:
+                if subprocess.call(['git', 'branch', '--track', local, remote],
                                    cwd=repo, stdout=devnull, stderr=devnull) == 0:
                     newly_tracked = True
         # Finally fetch any newly tracked remote branches
         if newly_tracked:
-            subprocess.check_call(["git", "fetch", "--quiet", "origin"], cwd=repo)
+            subprocess.check_call(['git', 'fetch', '--quiet', 'origin'], cwd=repo)
 
     def update(self, repo, rev, revname):
-        subprocess.check_call(["git", "checkout", "--quiet", revname], cwd=repo)
+        subprocess.check_call(['git', 'checkout', '--quiet', revname], cwd=repo)
 
     def ignore(self, target, repo):
         module = os.path.sep + os.path.relpath(target, repo)
-        exclude_file = os.path.join(repo, ".git", "info", "exclude")
+        exclude_file = os.path.join(repo, '.git', 'info', 'exclude')
         _ensure_line_exists(exclude_file, module)
 
     def postprocess_url(self, url):
         # Handle alternative syntax of SSH URLS
-        if "@" in url and ":" in url and not urlparse.urlsplit(url).scheme:
-            return "ssh://" + url.replace(":", "/", 1)
+        if '@' in url and ':' in url and not urlparse.urlsplit(url).scheme:
+            return 'ssh://' + url.replace(':', '/', 1)
         return url
 
 repo_types = OrderedDict((
-    ("hg", Mercurial()),
-    ("git", Git()),
+    ('hg', Mercurial()),
+    ('git', Git()),
 ))
 
 # [vcs:]value
 item_regexp = re.compile(
-    "^(?:(" + "|".join(map(re.escape, repo_types.keys())) + "):)?"
-    "(.+)$"
+    '^(?:(' + '|'.join(map(re.escape, repo_types.keys())) + '):)?'
+    '(.+)$'
 )
 
 # [url@]rev
 source_regexp = re.compile(
-    "^(?:(.*)@)?"
-    "(.+)$"
+    '^(?:(.*)@)?'
+    '(.+)$'
 )
 
 
 def merge_seqs(seq1, seq2):
     """Return a list of any truthy values from the suplied sequences
 
     (None, 2), (1,)      => [1, 2]
     None, (1, 2)         => [1, 2]
     (1, 2), (3, 4)       => [3, 4]
     """
     return map(lambda item1, item2: item2 or item1, seq1 or (), seq2 or ())
 
 
 def parse_spec(path, line):
-    if "=" not in line:
-        logging.warning("Invalid line in file %s: %s" % (path, line))
+    if '=' not in line:
+        logging.warning('Invalid line in file %s: %s' % (path, line))
         return None, None
 
-    key, value = line.split("=", 1)
+    key, value = line.split('=', 1)
     key = key.strip()
     items = value.split()
     if not len(items):
-        logging.warning("No value specified for key %s in file %s" % (key, path))
+        logging.warning('No value specified for key %s in file %s' % (key, path))
         return key, None
 
     result = OrderedDict()
-    is_dependency_field = not key.startswith("_")
+    is_dependency_field = not key.startswith('_')
 
     for i, item in enumerate(items):
         try:
             vcs, value = re.search(item_regexp, item).groups()
-            vcs = vcs or "*"
+            vcs = vcs or '*'
             if is_dependency_field:
-                if i == 0 and vcs == "*":
+                if i == 0 and vcs == '*':
                     # In order to be backwards compatible we have to assume that the first
                     # source contains only a URL/path for the repo if it does not contain
                     # the VCS part
                     url_rev = (value, None)
                 else:
                     url_rev = re.search(source_regexp, value).groups()
                 result[vcs] = merge_seqs(result.get(vcs), url_rev)
             else:
                 if vcs in result:
-                    logging.warning("Ignoring duplicate value for type %r "
-                                    "(key %r in file %r)" % (vcs, key, path))
+                    logging.warning('Ignoring duplicate value for type %r '
+                                    '(key %r in file %r)' % (vcs, key, path))
                 result[vcs] = value
         except AttributeError:
-            logging.warning("Ignoring invalid item %r for type %r "
-                            "(key %r in file %r)" % (item, vcs, key, path))
+            logging.warning('Ignoring invalid item %r for type %r '
+                            '(key %r in file %r)' % (item, vcs, key, path))
             continue
     return key, result
 
 
 def read_deps(repodir):
     result = {}
-    deps_path = os.path.join(repodir, "dependencies")
+    deps_path = os.path.join(repodir, 'dependencies')
     try:
-        with io.open(deps_path, "rt", encoding="utf-8") as handle:
+        with io.open(deps_path, 'rt', encoding='utf-8') as handle:
             for line in handle:
                 # Remove comments and whitespace
-                line = re.sub(r"#.*", "", line).strip()
+                line = re.sub(r'#.*', '', line).strip()
                 if not line:
                     continue
 
                 key, spec = parse_spec(deps_path, line)
                 if spec:
                     result[key] = spec
         return result
     except IOError, e:
@@ -226,155 +225,155 @@ def read_deps(repodir):
             raise
         return None
 
 
 def safe_join(path, subpath):
     # This has been inspired by Flask's safe_join() function
     forbidden = {os.sep, os.altsep} - {posixpath.sep, None}
     if any(sep in subpath for sep in forbidden):
-        raise Exception("Illegal directory separator in dependency path %s" % subpath)
+        raise Exception('Illegal directory separator in dependency path %s' % subpath)
 
     normpath = posixpath.normpath(subpath)
     if posixpath.isabs(normpath):
-        raise Exception("Dependency path %s cannot be absolute" % subpath)
+        raise Exception('Dependency path %s cannot be absolute' % subpath)
     if normpath == posixpath.pardir or normpath.startswith(posixpath.pardir + posixpath.sep):
-        raise Exception("Dependency path %s has to be inside the repository" % subpath)
+        raise Exception('Dependency path %s has to be inside the repository' % subpath)
     return os.path.join(path, *normpath.split(posixpath.sep))
 
 
 def get_repo_type(repo):
     for name, repotype in repo_types.iteritems():
         if repotype.istype(repo):
             return name
-    return "hg"
+    return 'hg'
 
 
 def ensure_repo(parentrepo, parenttype, target, type, root, sourcename):
     if os.path.exists(target):
         return
 
     if SKIP_DEPENDENCY_UPDATES:
-        logging.warning("SKIP_DEPENDENCY_UPDATES environment variable set, "
-                        "%s not cloned", target)
+        logging.warning('SKIP_DEPENDENCY_UPDATES environment variable set, '
+                        '%s not cloned', target)
         return
 
     postprocess_url = repo_types[type].postprocess_url
     root = postprocess_url(root)
     sourcename = postprocess_url(sourcename)
 
     if os.path.exists(root):
         url = os.path.join(root, sourcename)
     else:
         url = urlparse.urljoin(root, sourcename)
 
-    logging.info("Cloning repository %s into %s" % (url, target))
+    logging.info('Cloning repository %s into %s' % (url, target))
     repo_types[type].clone(url, target)
     repo_types[parenttype].ignore(target, parentrepo)
 
 
 def update_repo(target, type, revision):
     resolved_revision = repo_types[type].get_revision_id(target, revision)
     current_revision = repo_types[type].get_revision_id(target)
 
     if resolved_revision != current_revision:
         if SKIP_DEPENDENCY_UPDATES:
-            logging.warning("SKIP_DEPENDENCY_UPDATES environment variable set, "
-                            "%s not checked out to %s", target, revision)
+            logging.warning('SKIP_DEPENDENCY_UPDATES environment variable set, '
+                            '%s not checked out to %s', target, revision)
             return
 
         if not resolved_revision:
-            logging.info("Revision %s is unknown, downloading remote changes" % revision)
+            logging.info('Revision %s is unknown, downloading remote changes' % revision)
             repo_types[type].pull(target)
             resolved_revision = repo_types[type].get_revision_id(target, revision)
             if not resolved_revision:
-                raise Exception("Failed to resolve revision %s" % revision)
+                raise Exception('Failed to resolve revision %s' % revision)
 
-        logging.info("Updating repository %s to revision %s" % (target, resolved_revision))
+        logging.info('Updating repository %s to revision %s' % (target, resolved_revision))
         repo_types[type].update(target, resolved_revision, revision)
 
 
 def resolve_deps(repodir, level=0, self_update=True, overrideroots=None, skipdependencies=set()):
     config = read_deps(repodir)
     if config is None:
         if level == 0:
-            logging.warning("No dependencies file in directory %s, nothing to do...\n%s" % (repodir, USAGE))
+            logging.warning('No dependencies file in directory %s, nothing to do...\n%s' % (repodir, USAGE))
         return
     if level >= 10:
-        logging.warning("Too much subrepository nesting, ignoring %s" % repo)
+        logging.warning('Too much subrepository nesting, ignoring %s' % repo)
         return
 
     if overrideroots is not None:
-        config["_root"] = overrideroots
+        config['_root'] = overrideroots
 
     for dir, sources in config.iteritems():
-        if (dir.startswith("_") or
+        if (dir.startswith('_') or
             skipdependencies.intersection([s[0] for s in sources if s[0]])):
             continue
 
         target = safe_join(repodir, dir)
         parenttype = get_repo_type(repodir)
-        _root = config.get("_root", {})
+        _root = config.get('_root', {})
 
         for key in sources.keys() + _root.keys():
-            if key == parenttype or key is None and vcs != "*":
+            if key == parenttype or key is None and vcs != '*':
                 vcs = key
-        source, rev = merge_seqs(sources.get("*"), sources.get(vcs))
+        source, rev = merge_seqs(sources.get('*'), sources.get(vcs))
 
         if not (vcs and source and rev):
-            logging.warning("No valid source / revision found to create %s" % target)
+            logging.warning('No valid source / revision found to create %s' % target)
             continue
 
-        ensure_repo(repodir, parenttype, target, vcs, _root.get(vcs, ""), source)
+        ensure_repo(repodir, parenttype, target, vcs, _root.get(vcs, ''), source)
         update_repo(target, vcs, rev)
         resolve_deps(target, level + 1, self_update=False,
                      overrideroots=overrideroots, skipdependencies=skipdependencies)
 
-    if self_update and "_self" in config and "*" in config["_self"]:
-        source = safe_join(repodir, config["_self"]["*"])
+    if self_update and '_self' in config and '*' in config['_self']:
+        source = safe_join(repodir, config['_self']['*'])
         try:
-            with io.open(source, "rb") as handle:
+            with io.open(source, 'rb') as handle:
                 sourcedata = handle.read()
         except IOError, e:
             if e.errno != errno.ENOENT:
                 raise
             logging.warning("File %s doesn't exist, skipping self-update" % source)
             return
 
         target = __file__
-        with io.open(target, "rb") as handle:
+        with io.open(target, 'rb') as handle:
             targetdata = handle.read()
 
         if sourcedata != targetdata:
             logging.info("Updating %s from %s, don't forget to commit" % (target, source))
-            with io.open(target, "wb") as handle:
+            with io.open(target, 'wb') as handle:
                 handle.write(sourcedata)
-            if __name__ == "__main__":
-                logging.info("Restarting %s" % target)
+            if __name__ == '__main__':
+                logging.info('Restarting %s' % target)
                 os.execv(sys.executable, [sys.executable, target] + sys.argv[1:])
             else:
-                logging.warning("Cannot restart %s automatically, please rerun" % target)
+                logging.warning('Cannot restart %s automatically, please rerun' % target)
 
 
 def _ensure_line_exists(path, pattern):
     with open(path, 'a+') as f:
         file_content = [l.strip() for l in f.readlines()]
         if not pattern in file_content:
             file_content.append(pattern)
             f.seek(0, os.SEEK_SET)
             f.truncate()
             for l in file_content:
                 print >>f, l
 
-if __name__ == "__main__":
+if __name__ == '__main__':
     logging.basicConfig(format='%(levelname)s: %(message)s', level=logging.INFO)
 
-    parser = argparse.ArgumentParser(description="Verify dependencies for a set of repositories, by default the repository of this script.")
-    parser.add_argument("repos", metavar="repository", type=str, nargs="*", help="Repository path")
-    parser.add_argument("-q", "--quiet", action="store_true", help="Suppress informational output")
+    parser = argparse.ArgumentParser(description='Verify dependencies for a set of repositories, by default the repository of this script.')
+    parser.add_argument('repos', metavar='repository', type=str, nargs='*', help='Repository path')
+    parser.add_argument('-q', '--quiet', action='store_true', help='Suppress informational output')
     args = parser.parse_args()
 
     if args.quiet:
         logging.disable(logging.INFO)
 
     repos = args.repos
     if not len(repos):
         repos = [os.path.dirname(__file__)]