Add a ThriftInfo provider (#464)

* Add a ThriftInfo provider

* minor cleanup

* address review comments

Author: johnynek

thrift/thrift.bzl

@@ -2,6 +2,14 @@
 
 _thrift_filetype = FileType([".thrift"])
 
+ThriftInfo = provider(
+    fields=[
+        "srcs", # The source files in this rule
+        "transitive_srcs", # the transitive version of the above
+        "external_jars", # external jars of thrift files
+        "transitive_external_jars" # transitive version of the above
+    ])
+
 def _common_prefix(strings):
   pref = None
   for s in strings:
@@ -87,30 +95,29 @@ rm {out}.contents
     jarfiles.append(depset(jar.files))
   transitive_external_jars = depset(transitive = jarfiles)
 
-  return struct(
-    thrift = struct(
-      srcs = ctx.outputs.libarchive,
-      transitive_srcs = transitive_srcs,
-      external_jars = ctx.attr.external_jars,
-      transitive_external_jars = transitive_external_jars,
-    ),
-  )
+  return [
+      ThriftInfo(
+        srcs = ctx.outputs.libarchive,
+        transitive_srcs = transitive_srcs,
+        external_jars = ctx.attr.external_jars,
+        transitive_external_jars = transitive_external_jars,
+      )]
 
-def _collect_thrift_attr_depsets(targets, attr):
+def _collect_thrift_srcs(targets):
   ds = []
   for target in targets:
-    ds.append(getattr(target.thrift, attr))
+    ds.append(target[ThriftInfo].transitive_srcs)
   return ds
 
-def _collect_thrift_srcs(targets):
-  return _collect_thrift_attr_depsets(targets, "transitive_srcs")
-
 def _collect_thrift_external_jars(targets):
-  return _collect_thrift_attr_depsets(targets, "transitive_external_jars")
+  ds = []
+  for target in targets:
+    ds.append(target[ThriftInfo].transitive_external_jars)
+  return ds
 
 def _valid_thrift_deps(targets):
   for target in targets:
-    if not hasattr(target, "thrift"):
+    if not ThriftInfo in target:
       fail("thrift_library can only depend on thrift_library", target)
 
 # Some notes on the raison d'etre of thrift_library vs. code gen specific

twitter_scrooge/twitter_scrooge.bzl

@@ -5,6 +5,8 @@ load("//scala:scala.bzl",
   "collect_srcjars",
   "collect_jars")
 
+load("//thrift:thrift.bzl", "ThriftInfo")
+
 _jar_filetype = FileType([".jar"])
 
 def twitter_scrooge():
@@ -57,8 +59,8 @@ def twitter_scrooge():
 def _collect_transitive_srcs(targets):
   r = []
   for target in targets:
-    if hasattr(target, "thrift"):
-      r.append(target.thrift.transitive_srcs)
+    if ThriftInfo in target:
+      r.append(target[ThriftInfo].transitive_srcs)
   return depset(transitive = r)
 
 def _collect_owned_srcs(targets):
@@ -73,13 +75,12 @@ def _collect_owned_srcs(targets):
 def _collect_external_jars(targets):
   r = []
   for target in targets:
-    if hasattr(target, "thrift"):
-      thrift = target.thrift
-      if hasattr(thrift, "external_jars"):
-        for jar in thrift.external_jars:
-          r.append(depset(_jar_filetype.filter(jar.files)))
-      r.append(depset(_jar_filetype.filter(thrift.transitive_external_jars)))
-  return depset(transitive = r)
+    if ThriftInfo in target:
+      thrift = target[ThriftInfo]
+      for jar in thrift.external_jars:
+        r.extend(_jar_filetype.filter(jar.files))
+      r.extend(_jar_filetype.filter(thrift.transitive_external_jars))
+  return depset(r)
 
 def collect_extra_srcjars(targets):
   srcjar = []
@@ -92,11 +93,11 @@ def collect_extra_srcjars(targets):
   return depset(srcjar, transitive = srcjars)
 
 def _collect_immediate_srcs(targets):
-  r = []
+  srcs = []
   for target in targets:
-    if hasattr(target, "thrift"):
-      r.append(depset([target.thrift.srcs]))
-  return depset(transitive = r)
+    if ThriftInfo in target:
+      srcs.append(target[ThriftInfo].srcs)
+  return depset(srcs)
 
 def _assert_set_is_subset(want, have):
   missing = []