Implement a first pass of `gclient flatten`.

gclient.py

Index: gclient.py
diff --git a/gclient.py b/gclient.py
index 3e8a7962290a3b63832adc2ad3469ae7ad2d6a53..6676a46d3d2cedc14de3fbffc9aa60cfcb1a57ec 100755
--- a/gclient.py
+++ b/gclient.py
@@ -761,7 +761,7 @@ class Dependency(gclient_utils.WorkItem, DependencySettings):
     # When running runhooks, there's no need to consult the SCM.
     # All known hooks are expected to run unconditionally regardless of working
     # copy state, so skip the SCM status check.
-    run_scm = command not in ('runhooks', 'recurse', None)
+    run_scm = command not in ('flatten', 'runhooks', 'recurse', None)
     parsed_url = self.LateOverride(self.url)
     file_list = [] if not options.nohooks else None
     revision_override = revision_overrides.pop(self.name, None)
@@ -1655,6 +1655,98 @@ def CMDrecurse(parser, args):
                           progress=not options.no_progress)
 
 
+@subcommand.usage('[command] [--verify] [args ...]')
+def CMDflatten(parser, args):
+  """Flattens the solutions into a single DEPS file."""
+  # Stop parsing at the first non-arg so that these go through to the command
+  parser.add_option('--verify', action='store_true',
+                    help='Verifies that each dependencies is pinned at a '
+                         'specific revision.')

[agable, 2016/11/02 17:53:26]

And that the .gclient_entries file matches what's actually on the filesystem,
maybe?

[Dirk Pranke, 2016/11/02 19:01:22]

I'm not sure how useful that is, but I'm not actually sure what all
.gclient_entries is even used for?

[Michael Moss, 2016/11/02 20:50:30]

Assuming --verify ends up using gitiles requests, it wouldn't necessarily work
as the same command to verify a checkout, but we could have two types of
verification. Maybe --validate (syntax and hashes) and --fsck (with it's implied
meaning of checking stuff on disk), or something like that.

+  options, args = parser.parse_args(args)
+  root_and_entries = gclient_utils.GetGClientRootAndEntries()
+  if not root_and_entries:
+    print(
+        'You need to run gclient sync at least once to use \'flatten\'.\n'
+        'This is because .gclient_entries needs to exist and be up to date.',
+        file=sys.stderr)
+    return 1
+
+  options.nohooks = True
+  client = GClient.LoadCurrentConfig(options)
+  res = client.RunOnDeps('flatten', args, ignore_requirements=True,
+                         progress=False)
+  if res:
+    return res
+
+  deps = {}
+  hooks = []
+  unpinned_deps = {}
+
+  for solution in client.dependencies:
+    _FlattenSolution(solution, deps, hooks, unpinned_deps)
+
+  if options.verify and unpinned_deps:
+    for name in unpinned_deps:
+      print("'%s' is not pinned to a Git revision" % name)
+    return 1
+
+  flattened_deps = ('%s\n%s\n' %
+                    (_DepsToVarString(deps), _HooksToVarString(hooks)))
+  print(flattened_deps)
+  return 0
+
+
+def _FlattenSolution(solution, deps, hooks, unpinned_deps):
+  _AddDep(solution, deps, unpinned_deps)
+  for dep in solution.dependencies:
+    _FlattenDep(dep, deps, hooks, unpinned_deps)
+  hooks.extend(solution.deps_hooks)
+
+
+def _FlattenDep(dep, deps, hooks, unpinned_deps):
+  _AddDep(dep, deps, unpinned_deps)
+  for recurse_dep_name in sorted(dep.recursedeps or []):
+    for sub_dep in dep.dependencies:
+      if recurse_dep_name == dep.name:
+        _FlattenDep(sub_dep, deps, hooks, unpinned_deps)
+      break
+  hooks.extend(dep.deps_hooks)
+
+
+def _AddDep(dep, deps, unpinned_deps):
+  assert dep.name not in deps
+  deps[dep.name] = dep.url
+  _, revision = gclient_utils.SplitUrlRevision(dep.url)
+  if not revision or not gclient_utils.IsGitSha(revision):
+    unpinned_deps[dep.name] = dep.url
+
+
+def _DepsToVarString(deps):
+  s = "deps = {\n"
+  for name in sorted(deps):
+    s += "  '%s': '%s',\n" % (name, deps[name])
+  s += "}\n"
+  return s
+
+
+def _HooksToVarString(hooks):
+  s = "hooks = [\n"
+  for hook in hooks:
+    s += "  {\n"

[agable, 2016/11/02 17:53:26]

Make this a triple-quoted multi-line template string rather than doing lots of
string concatenation.

[Dirk Pranke, 2016/11/02 19:01:22]

I originally didn't do this because I thought handling the conditionals would
make this harder to read. But I'll code up something and we can compare.

+    if 'name' in hook:
+      s += "    'name': '%s',\n" % hook['name']
+    if 'pattern' in hook:
+      s += "    'pattern': '%s',\n" % hook['pattern']
+    s += "    'action': [\n"
+    s += "      "
+    s += ",\n      ".join("'%s'" % arg for arg in hook['action'])
+    s += ",\n"
+    s += "    ],\n"
+    s += "  },\n"
+  s += "}"
+  return s
+
+
 @subcommand.usage('[args ...]')
 def CMDfetch(parser, args):
   """Fetches upstream commits for all modules.