Add text_search parameter to discussion API

The thread list endpoint now accepts the text_search parameter and also
includes a text_search_rewrite field in its responses.

lms/djangoapps/discussion_api/tests/test_forms.py

@@ -1,9 +1,12 @@
 """
 Tests for Discussion API forms
 """
+import itertools
 from unittest import TestCase
 from urllib import urlencode
 
+import ddt
+
 from django.http import QueryDict
 
 from opaque_keys.edx.locator import CourseLocator
@@ -63,6 +66,7 @@ class PaginationTestMixin(object):
         self.assert_field_value("page_size", 100)
 
 
+@ddt.ddt
 class ThreadListGetFormTest(FormTestMixin, PaginationTestMixin, TestCase):
     """Tests for ThreadListGetForm"""
     FORM_CLASS = ThreadListGetForm
@@ -81,7 +85,6 @@ class ThreadListGetFormTest(FormTestMixin, PaginationTestMixin, TestCase):
         )
 
     def test_basic(self):
-        self.form_data.setlist("topic_id", ["example topic_id", "example 2nd topic_id"])
         form = self.get_form(expected_valid=True)
         self.assertEqual(
             form.cleaned_data,
@@ -89,10 +92,27 @@ class ThreadListGetFormTest(FormTestMixin, PaginationTestMixin, TestCase):
                 "course_id": CourseLocator.from_string("Foo/Bar/Baz"),
                 "page": 2,
                 "page_size": 13,
-                "topic_id": ["example topic_id", "example 2nd topic_id"],
+                "topic_id": [],
+                "text_search": "",
             }
         )
 
+    def test_topic_id(self):
+        self.form_data.setlist("topic_id", ["example topic_id", "example 2nd topic_id"])
+        form = self.get_form(expected_valid=True)
+        self.assertEqual(
+            form.cleaned_data["topic_id"],
+            ["example topic_id", "example 2nd topic_id"],
+        )
+
+    def test_text_search(self):
+        self.form_data["text_search"] = "test search string"
+        form = self.get_form(expected_valid=True)
+        self.assertEqual(
+            form.cleaned_data["text_search"],
+            "test search string",
+        )
+
     def test_missing_course_id(self):
         self.form_data.pop("course_id")
         self.assert_error("course_id", "This field is required.")
@@ -105,6 +125,14 @@ class ThreadListGetFormTest(FormTestMixin, PaginationTestMixin, TestCase):
         self.form_data.setlist("topic_id", ["", "not empty"])
         self.assert_error("topic_id", "This field cannot be empty.")
 
+    @ddt.data(*itertools.combinations(["topic_id", "text_search"], 2))
+    def test_mutually_exclusive(self, params):
+        self.form_data.update({param: "dummy" for param in params})
+        self.assert_error(
+            "__all__",
+            "The following query parameters are mutually exclusive: topic_id, text_search"
+        )
+
 
 class CommentListGetFormTest(FormTestMixin, PaginationTestMixin, TestCase):
     """Tests for CommentListGetForm"""