Add check for whether the soy docs compile

Summary:
This adds a script which runs the plovr build to check
soy doc syntax.

Test Plan:
1. Make sure `ant verify-soydoc; buck test //docs:` succeed,
2. Introduce syntax error into rust_binary.soy
3. Make sure commands from 1. fail

Reviewed By: mjpieters

fbshipit-source-id: a969c40

build.xml

@@ -986,7 +986,13 @@
     </exec>
   </target>
 
-  <target name="travis" depends="verify-javadoc, lint" />
+  <target name="verify-soydoc"
+          description="verify that soy docs can be generated without errors">
+    <exec executable="${basedir}/docs/soy_syntax_check.py" failonerror="true">
+    </exec>
+  </target>
+
+  <target name="travis" depends="verify-javadoc, verify-soydoc, lint" />
 
   <target name="pre-checkin" depends="clean, default, compile-tests, lint"/>
   <target name="all" depends="jar, test, javadoc" />

docs/BUCK

@@ -0,0 +1,7 @@
+python_test(
+  name='soy_docs_syntax',
+  srcs = [
+    'soy_syntax_check.py',
+  ],
+  resources = glob(['**/*.soy', '*.jar']),
+)

docs/soy_syntax_check.py

@@ -0,0 +1,63 @@
+#!/usr/bin/env python
+#
+# This script runs the plovr build to make sure none of the soy files
+# have syntax errors.
+
+import json
+import os
+import subprocess
+import tempfile
+import unittest
+
+PLOVR_JAR = 'plovr-81ed862.jar'
+
+
+def find_docs_dir():
+    cwd = os.path.dirname(os.path.realpath(__file__))
+    prev_cwd = None
+    while cwd != prev_cwd:
+        if os.path.exists(os.path.join(cwd, 'docs', PLOVR_JAR)):
+            return os.path.join(cwd, 'docs')
+        prev_cwd = cwd
+        cwd = os.path.dirname(cwd)
+    raise Exception('Could not find plovr jar')
+
+
+def main():
+    docs_dir = find_docs_dir()
+    input_files = []
+    for root, dirs, files in os.walk(docs_dir):
+        for file_name in files:
+            if file_name.endswith('.soy') and not file_name.startswith('__'):
+                input_files.append(os.path.join(root, file_name))
+    print('Building %s soy files.' % len(input_files))
+    config_data = {
+        'id': 'buck',
+        # This removes the warning about param being a reserved JS keyword.
+        'experimental-compiler-options': {
+            'languageIn': 'ECMASCRIPT5',
+         },
+        'paths': docs_dir,
+        'inputs': input_files,
+    }
+
+    plovr_abspath = os.path.join(docs_dir, PLOVR_JAR)
+    fd, config_path = tempfile.mkstemp(suffix='.json', prefix='plovr_config')
+    try:
+        with open(config_path, 'w') as config_file:
+            json.dump(config_data, config_file)
+        subprocess.check_output([
+            'java', '-jar', plovr_abspath, 'build', config_path
+        ])
+    finally:
+        os.close(fd)
+        os.unlink(config_path)
+
+
+class TestBuckPackage(unittest.TestCase):
+    def test_no_soy_doc_syntax_error(self):
+        main()
+
+
+if __name__ == '__main__':
+    unittest.main()