Show enclosing schema on schema name resolution error

Summary:
If a schema name is unknown, glean throws an error and prints the wrong name, but not where it occurred

> gen-schema: unknown schema: hs.2

This diff fixes that

Reviewed By: jjuliamolin

Differential Revision: D75794770

fbshipit-source-id: c394286cd70f8c325625d584619b07f9d6f426fe

Author: Roman Castellarin

glean/hs/Glean/Schema/Resolve.hs

@@ -217,15 +217,20 @@ resolveSchemaRefs SourceSchemas{..} = do
        where
        unknown = throwError $ "unknown schema: " <> showRef ref
 
-     resolveDecl (SourceImport r s) = SourceImport <$> schemaByName r <*> pure s
-     resolveDecl decl = return decl
+     schemaByNameWithNamespace parentSchema ref =
+       let message e = e <> " within schema: " <> showRef parentSchema
+       in withExcept message (schemaByName ref)
+
+     resolveDecl parentSchema (SourceImport r s) =
+      SourceImport <$> schemaByNameWithNamespace parentSchema r <*> pure s
+     resolveDecl _ decl = return decl
 
      resolveEvolve (SourceEvolves l n o) =
        SourceEvolves l <$> schemaByName n <*> schemaByName o
 
      resolveSchema SourceSchema{..} = do
-       inherits <- mapM schemaByName schemaInherits
-       decls <- mapM resolveDecl schemaDecls
+       inherits <- mapM (schemaByNameWithNamespace schemaName) schemaInherits
+       decls <- mapM (resolveDecl schemaName) schemaDecls
        return SourceSchema
          { schemaName = schemaName
          , schemaInherits = inherits