Handle selecting from maybe types with .just?/.nothing?

Reviewed By: malanka

Differential Revision: D59368949

fbshipit-source-id: b602d49e4a85ee5417d5460da2f58e3d63d434f2

glean/db/Glean/Query/Typecheck.hs

@@ -409,6 +409,8 @@ fieldSelect src ty pat fieldName sum = do
       | otherwise -> err $
         "expression is a union type, use '." <> pretty fieldName <>
           "?' not '." <> pretty fieldName <> "'"
+    MaybeTy elemTy ->
+      fieldSelect src (lowerMaybe elemTy) pat fieldName sum
     _ -> err $ "expression is not a " <> if sum then "union type" else "record"
 
 convertType

glean/test/lib/TestData.hs

@@ -99,7 +99,7 @@ mkTestFacts first second = do
       , Glean.Test.kitchenSink_array_of_string = ["abba", "baba"]
       , Glean.Test.kitchenSink_named_sum_ = Glean.Test.Sum_wed True
       , Glean.Test.kitchenSink_named_record_ = rec
-      , Glean.Test.kitchenSink_maybe_ = Nothing
+      , Glean.Test.kitchenSink_maybe_ = Just def
       }
 
     -- also make a small variant of kitchenSink2Term0

glean/test/tests/Angle/AngleTest.hs

@@ -856,6 +856,11 @@ angleDotTest = dbTestCase $ \env repo -> do
     "X.sum_.c?.string_ where glean.test.Predicate X"
   assertEqual "dot record.sum.record" ["abba", "acca"] r
 
+  -- maybe
+  r <- runQuery_ env repo $ angleData @Text
+    "X.string_ where (X : glean.test.Predicate).maybe_.just?"
+  assertEqual "dot maybe" ["abba", "acca"] r
+
   -- error: field not found
   r <- try $ runQuery env repo $ angleData @Text
     "X.notfound where glean.test.Predicate X"