Add context for error; fix for Issue #9751 (#12633)

* Add context for error; fix for Issue #9751

* translate TypeError into a user friendly error message

* test for unexpected results from search

* fixed broken unexpected results test

Author: adam248

conans/client/rest/rest_client_common.py

@@ -242,7 +242,12 @@ def search(self, pattern=None, ignorecase=True):
         """
         url = self.router.search(pattern, ignorecase)
         response = self.get_json(url)["results"]
-        return [ConanFileReference.loads(reference) for reference in response]
+        try:
+            return [ConanFileReference.loads(reference) for reference in response]
+        except TypeError as te:
+            raise ConanException("Unexpected response from server.\n"
+                                 "URL: `{}`\n"
+                                 "Expected an iterable, but got {}.".format(url, type(response)))
 
     def search_packages(self, ref):
         """Client is filtering by the query"""

conans/test/unittests/client/rest/rest_client_v1/test_get_package_manifest.py

@@ -33,3 +33,15 @@ def test_corrupted_manifest(self):
                           " from remote ({})".format(pref, remote_url),
                           str(exc.exception))
             self.assertIn("invalid literal for int() with base 10", str(exc.exception))
+
+    def test_unexpected_results_from_search(self):
+        remote_url = "http://some.url"
+        with patch.object(RestV1Methods, "get_json", return_value={"results": None}):
+            v1 = RestV1Methods(remote_url, token=None, custom_headers=None, output=None,
+                               requester=None, config=None, verify_ssl=None)
+            with self.assertRaises(ConanException) as exc:
+                v1.search()
+            
+            self.assertIn("Unexpected response from server.\n"
+                          "URL: `http://some.url/v1/conans/search`\n"
+                          "Expected an iterable, but got <class 'NoneType'>.", str(exc.exception))

conans/test/unittests/client/rest/rest_client_v2/test_get_package_manifest.py

@@ -30,3 +30,15 @@ def test_corrupted_manifest(self):
                           " from remote ({})".format(pref.full_str(), remote_url),
                           str(exc.exception))
             self.assertIn("invalid literal for int() with base 10", str(exc.exception))
+
+    def test_unexpected_results_from_search(self):
+        remote_url = "http://some.url"
+        with patch.object(RestV2Methods, "get_json", return_value={"results": None}):
+            v2 = RestV2Methods(remote_url, token=None, custom_headers=None, output=None,
+                               requester=None, config=None, verify_ssl=None)
+            with self.assertRaises(ConanException) as exc:
+                v2.search()
+            
+            self.assertIn("Unexpected response from server.\n"
+                          "URL: `http://some.url/v2/conans/search`\n"
+                          "Expected an iterable, but got <class 'NoneType'>.", str(exc.exception))