build(bazel): add entry_point_name attr to ng_package

packages/bazel/src/ng_package/ng_package.bzl

@@ -258,6 +258,9 @@ NG_PACKAGE_ATTRS = dict(NPM_PACKAGE_ATTRS, **dict(ROLLUP_ATTRS, **{
     "include_devmode_srcs": attr.bool(default = False),
     "readme_md": attr.label(allow_single_file = FileType([".md"])),
     "globals": attr.string_dict(default={}),
+    "entry_point_name": attr.string(
+      doc = "Name to use when generating bundle files for the primary entry-point.",
+    ),
     "_ng_packager": attr.label(
         default=Label("//packages/bazel/src/ng_package:packager"),
         executable=True, cfg="host"),
@@ -278,11 +281,15 @@ NG_PACKAGE_ATTRS = dict(NPM_PACKAGE_ATTRS, **dict(ROLLUP_ATTRS, **{
 # Currently we just borrow the entry point for this, if it looks like
 # some/path/to/my/package/index.js
 # we assume the files should be named "package.*.js"
-def primary_entry_point_name(name, entry_point):
-  return entry_point.split("/")[-2] if entry_point.find("/") >=0 else name
+def primary_entry_point_name(name, entry_point, entry_point_name):
+  # If an explicit entry_point_name is given, use that.
+  if entry_point_name:
+      return entry_point_name
+  else:
+      return entry_point.split("/")[-2] if entry_point.find("/") >=0 else name
 
-def ng_package_outputs(name, entry_point):
-  basename = primary_entry_point_name(name, entry_point)
+def ng_package_outputs(name, entry_point, entry_point_name):
+  basename = primary_entry_point_name(name, entry_point, entry_point_name)
   outputs = {
       "fesm5": "fesm5/%s.js" % basename,
       "fesm2015": "fesm2015/%s.js" % basename,