json: Return a `JsonParseError` on failure.

Distinguish an error from `null`.

Signed-off-by: Jean-Christophe Beaupré <jcbrinfo@users.noreply.github.com>

diff --git a/lib/json/static.nit b/lib/json/static.nit
index 4ebf1c0..4841020 100644 (file)
--- a/lib/json/static.nit
+++ b/lib/json/static.nit
@@ -23,7 +23,7 @@
 # languages features (`isa` and `as`).
 module static
 
-import standard
+import error
 private import json_parser
 private import json_lexer
 
@@ -83,14 +83,8 @@ redef class Text
                var root_node = parser.parse
                if root_node isa NStart then
                        return root_node.n_0.to_nit_object
-               else if root_node isa NLexerError then
-                       var pos = root_node.position
-                       print "Json lexer error: {root_node.message} at {pos or else "<unknown>"} for {root_node}"
-                       return null
-               else if root_node isa NParserError then
-                       var pos = root_node.position
-                       print "Json parsing error: {root_node.message} at {pos or else "<unknown>"} for {root_node}"
-                       return null
+               else if root_node isa NError then
+                       return new JsonParseError(root_node.message, root_node.position)
                else abort
        end
 end
@@ -232,6 +226,43 @@ class JsonArray
        super Array[nullable Jsonable]
 end
 
+redef class JsonParseError
+       super Jsonable
+
+       # Get the JSON representation of `self`.
+       #
+       #     var err = new JsonParseError("foo", new Position(1, 2, 3, 4, 5, 6))
+       #     assert err.to_json == "\{\"error\":\"JsonParseError\"," +
+       #               "\"position\":\{" +
+       #                       "\"pos_start\":1,\"pos_end\":2," +
+       #                       "\"line_start\":3,\"line_end\":4," +
+       #                       "\"col_start\":5,\"col_end\":6" +
+       #               "\},\"message\":\"foo\"\}"
+       redef fun to_json do
+               return "\{\"error\":\"JsonParseError\"," +
+                               "\"position\":{position.to_json}," +
+                               "\"message\":{message.to_json}\}"
+       end
+end
+
+redef class Position
+       super Jsonable
+
+       # Get the JSON representation of `self`.
+       #
+       #     var pos = new Position(1, 2, 3, 4, 5, 6)
+       #     assert pos.to_json == "\{" +
+       #                       "\"pos_start\":1,\"pos_end\":2," +
+       #                       "\"line_start\":3,\"line_end\":4," +
+       #                       "\"col_start\":5,\"col_end\":6" +
+       #               "\}"
+       redef fun to_json do
+               return "\{\"pos_start\":{pos_start},\"pos_end\":{pos_end}," +
+                               "\"line_start\":{line_start},\"line_end\":{line_end}," +
+                               "\"col_start\":{col_start},\"col_end\":{col_end}\}"
+       end
+end
+
 ################################################################################
 # Redef parser