cr: Print a list of closest matching targets when no match is found

When the user passes in an invalid target name, print a list of closest
matches as a hint:

    $ cr build chromium_test_shell
    Invalid target chromium_test_shell as chromium_test_shell
    Did you mean chromium_testshell, libchromiumtestshell or chromium_testshell_paks?

NOTRY=true

Review URL: https://codereview.chromium.org/136553002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@244507 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 12 insertions, 0 deletions

diff --git a/tools/cr/cr/actions/builder.py b/tools/cr/cr/actions/builder.py
index 74959af..286d2ec 100644
--- a/tools/cr/cr/actions/builder.py
+++ b/tools/cr/cr/actions/builder.py
@@ -4,6 +4,8 @@
 
 """A module for the Builder base class."""
 
+import difflib
+
 import cr
 
 
@@ -56,6 +58,11 @@ class Builder(cr.Action, cr.Plugin.Type):
     """Check if a target name is on the builder knows about."""
     return target_name in self.GetTargets(context)
 
+  @cr.Plugin.activemethod
+  def GuessTargets(self, context, target_name):
+    """Returns a list of closest matching targets for a named target."""
+    return difflib.get_close_matches(target_name, self.GetTargets(context))
+
 
 class SkipBuilder(Builder):
   """The "skip" version of a Builder, causes the build step to be skipped."""
diff --git a/tools/cr/cr/targets/target.py b/tools/cr/cr/targets/target.py
index e02bdb0..0780ae9 100644
--- a/tools/cr/cr/targets/target.py
+++ b/tools/cr/cr/targets/target.py
@@ -117,6 +117,11 @@ class Target(cr.Config, cr.AutoExport):
         if not target.valid:
           print 'Invalid target {0} as {1}'.format(
               target_name, target.build_target)
+          guesses = cr.Builder.GuessTargets(context, target_name)
+          if guesses:
+            print 'Did you mean {0}?'.format(
+                ', '.join(guesses[:-1]) + ' or ' + guesses[-1]
+                if len(guesses) > 1 else guesses[0])
           exit(1)
         return target
     print 'Unknown target {0}'.format(target_name)