Add a tool to check license compatibility with Android

tools/licenses.py

Index: tools/licenses.py
diff --git a/tools/licenses.py b/tools/licenses.py
index b01db489da107bfd599742db55a4bb243c092558..4ac2aa468f3bcf61e7462535403becf64c7548c7 100755
--- a/tools/licenses.py
+++ b/tools/licenses.py
@@ -173,8 +173,14 @@ def AbsolutePath(path, filename):
         return absolute_path
     return None
 
-def ParseDir(path):
-    """Examine a third_party/foo component and extract its metadata."""
+def ParseDir(path, raise_on_error):
+    """Examine a third_party/foo component and extract its metadata.
+    Args:
+      path the path to the component to examine
+      raise_on_error whether to raise an exception if an error occurs
+    Returns:
+      metadata for the component
+    """
 
     # Parse metadata fields out of README.chromium.
     # We examine "LICENSE" for the license file by default.
@@ -194,23 +200,25 @@ def ParseDir(path):
         # Try to find README.chromium.
         readme_path = os.path.join(path, 'README.chromium')
         if not os.path.exists(readme_path):
-            raise LicenseError("missing README.chromium")
-
-        for line in open(readme_path):
-            line = line.strip()
-            if not line:
-                break
-            for key in metadata.keys() + optional_keys:
-                field = key + ": "
-                if line.startswith(field):
-                    metadata[key] = line[len(field):]
+            if raise_on_error:
+                raise LicenseError("missing README.chromium")
+        else:
+            for line in open(readme_path):
+                line = line.strip()
+                if not line:
+                    break
+                for key in metadata.keys() + optional_keys:
+                    field = key + ": "
+                    if line.startswith(field):
+                        metadata[key] = line[len(field):]
 
     # Check that all expected metadata is present.
-    for key, value in metadata.iteritems():
-        if not value:
-            raise LicenseError("couldn't find '" + key + "' line "
-                               "in README.chromium or licences.py "
-                               "SPECIAL_CASES")
+    if raise_on_error:
+        for key, value in metadata.iteritems():
+            if not value:
+                raise LicenseError("couldn't find '" + key + "' line "
+                                   "in README.chromium or licences.py "
+                                   "SPECIAL_CASES")
 
     # Check that the license file exists.
     for filename in (metadata["License File"], "COPYING"):
@@ -219,7 +227,7 @@ def ParseDir(path):
             metadata["License File"] = license_path
             break
 
-    if not license_path:
+    if raise_on_error and not license_path:
         raise LicenseError("License file not found. "
                            "Either add a file named LICENSE, "
                            "import upstream's COPYING if available, "
@@ -230,7 +238,7 @@ def ParseDir(path):
         required_path = AbsolutePath(path, metadata["Required Text"])
         if required_path is not None:
             metadata["Required Text"] = required_path
-        else:
+        elif raise_on_error:
             raise LicenseError("Required text file listed but not found.")
 
     return metadata
@@ -277,7 +285,7 @@ def ScanThirdPartyDirs():
     errors = []
     for path in sorted(third_party_dirs):
         try:
-            metadata = ParseDir(path)
+            metadata = ParseDir(path, True)

[Evan Martin, 2012/07/24 19:41:28]

Consider something like:
  ParseDir(path, raise_on_error=True)
to make the code more self-describing.  (here and below) 


But if the calling code really wants to swallow all LicenseErrors, why not just
wrap the call to ParseDir() with a "try" block that does so rather than passing
this bool?

[Steve Block, 2012/07/24 21:20:58]

Regarding a try block, this approach doesn't work because I need to method to
complete, even if one of the early phases fails and would otherwise raise.

         except LicenseError, e:
             errors.append((path, e.args[0]))
             continue
@@ -307,7 +315,7 @@ def GenerateCredits():
     entries = []
     for path in sorted(third_party_dirs):
         try:
-            metadata = ParseDir(path)
+            metadata = ParseDir(path, True)
         except LicenseError:
             print >>sys.stderr, ("WARNING: licensing info for " + path +
                                  " is incomplete, skipping.")