feat: Support accessing array items and fields of composite types through json operators

This is supported in select=, in filters and in order=.

Resolves #1543

Resolves #2075

Signed-off-by: Wolfgang Walther <walther@technowledgy.de>

src/PostgREST/Query/SqlFragment.hs

@@ -197,7 +197,10 @@ pgFmtColumn table "*" = fromQi table <> ".*"
 pgFmtColumn table c   = fromQi table <> "." <> pgFmtIdent c
 
 pgFmtField :: QualifiedIdentifier -> Field -> SQL.Snippet
-pgFmtField table (c, jp) = SQL.sql (pgFmtColumn table c) <> pgFmtJsonPath jp
+pgFmtField table (c, []) = SQL.sql (pgFmtColumn table c)
+-- Using to_jsonb instead of to_json to avoid missing operator errors when filtering:
+-- "operator does not exist: json = unknown"
+pgFmtField table (c, jp) = SQL.sql ("to_jsonb(" <> pgFmtColumn table c <> ")") <> pgFmtJsonPath jp
 
 pgFmtSelectItem :: QualifiedIdentifier -> SelectItem -> SQL.Snippet
 pgFmtSelectItem table (f@(fName, jp), Nothing, alias, _, _) = pgFmtField table f <> SQL.sql (pgFmtAs fName jp alias)

src/PostgREST/Request/QueryParams.hs

@@ -318,6 +318,26 @@ pFieldName =
     dash :: Parser Char
     dash = isDash $> '-'
 
+-- |
+-- Parse json operators in select, order and filters
+--
+-- >>> P.parse pJsonPath "" "->text"
+-- Right [JArrow {jOp = JKey {jVal = "text"}}]
+--
+-- >>> P.parse pJsonPath "" "->1"
+-- Right [JArrow {jOp = JIdx {jVal = "+1"}}]
+--
+-- >>> P.parse pJsonPath "" "->>text"
+-- Right [J2Arrow {jOp = JKey {jVal = "text"}}]
+--
+-- >>> P.parse pJsonPath "" "->>1"
+-- Right [J2Arrow {jOp = JIdx {jVal = "+1"}}]
+--
+-- >>> P.parse pJsonPath "" "->0,other"
+-- Right [JArrow {jOp = JIdx {jVal = "+0"}}]
+--
+-- >>> P.parse pJsonPath "" "->0.desc"
+-- Right [JArrow {jOp = JIdx {jVal = "+0"}}]
 pJsonPath :: Parser JsonPath
 pJsonPath = many pJsonOperation
   where
@@ -333,6 +353,8 @@ pJsonPath = many pJsonOperation
           pJIdx = JIdx . toS <$> ((:) <$> P.option '+' (char '-') <*> many1 digit) <* pEnd
           pEnd = try (void $ lookAhead (string "->")) <|>
                  try (void $ lookAhead (string "::")) <|>
+                 try (void $ lookAhead (string ".")) <|>
+                 try (void $ lookAhead (string ",")) <|>
                  try eof in
       try pJIdx <|> try pJKey