Add Error format support, and JSON output option

mypy/build.py

@@ -254,7 +254,7 @@ def _build(
         plugin=plugin,
         plugins_snapshot=snapshot,
         errors=errors,
-        error_formatter=OUTPUT_CHOICES.get(options.output),
+        error_formatter=None if options.output is None else OUTPUT_CHOICES.get(options.output),
         flush_errors=flush_errors,
         fscache=fscache,
         stdout=stdout,

mypy/error_formatter.py

@@ -27,8 +27,9 @@ def report_error(self, error: "MypyError") -> str:
                 "line": error.line,
                 "column": error.column,
                 "message": error.message,
-                "hint": error.hint or None,
+                "hint": None if len(error.hints) == 0 else "\n".join(error.hints),
                 "code": None if error.errorcode is None else error.errorcode.code,
+                "is_note": error.is_note,
             }
         )
 

mypy/errors.py

@@ -1295,15 +1295,16 @@ def __init__(
         line: int,
         column: int,
         message: str,
-        hint: str,
         errorcode: ErrorCode | None,
+        is_note: bool = False,
     ) -> None:
         self.file_path = file_path
         self.line = line
         self.column = column
         self.message = message
-        self.hint = hint
         self.errorcode = errorcode
+        self.is_note = is_note
+        self.hints: list[str] = []
 
 
 # (file_path, line, column)
@@ -1324,16 +1325,15 @@ def create_errors(error_tuples: list[ErrorTuple]) -> list[MypyError]:
             error_location = (file_path, line, column)
             error = latest_error_at_location.get(error_location)
             if error is None:
-                # No error tuple found for this hint. Ignoring it
+                # This is purely a note, with no error correlated to it
+                error = MypyError(file_path, line, column, message, errorcode, is_note=True)
+                errors.append(error)
                 continue
 
-            if error.hint == "":
-                error.hint = message
-            else:
-                error.hint += "\n" + message
+            error.hints.append(message)
 
         else:
-            error = MypyError(file_path, line, column, message, "", errorcode)
+            error = MypyError(file_path, line, column, message, errorcode)
             errors.append(error)
             error_location = (file_path, line, column)
             latest_error_at_location[error_location] = error

mypy/options.py

@@ -380,7 +380,7 @@ def __init__(self) -> None:
         self.force_union_syntax = False
 
         # Sets custom output format
-        self.output = ""
+        self.output: str | None = None
 
     def use_lowercase_names(self) -> bool:
         if self.python_version >= (3, 9):

test-data/unit/outputjson.test

@@ -18,7 +18,7 @@ def foo() -> None:
 
 foo(1)
 [out]
-{"file": "main", "line": 5, "column": 0, "message": "Too many arguments for \"foo\"", "hint": null, "code": "call-arg"}
+{"file": "main", "line": 5, "column": 0, "message": "Too many arguments for \"foo\"", "hint": null, "code": "call-arg", "is_note": false}
 
 [case testOutputJsonWithHint]
 # flags: --output=json
@@ -32,10 +32,13 @@ def foo(x: int) -> None: ...
 def foo(x: Optional[int] = None) -> None:
     ...
 
+reveal_type(foo)
+
 foo('42')
 
 def bar() -> None: ...
 bar('42')
 [out]
-{"file": "main", "line": 12, "column": 0, "message": "No overload variant of \"foo\" matches argument type \"str\"", "hint": "Possible overload variants:\n    def foo() -> None\n    def foo(x: int) -> None", "code": "call-overload"}
-{"file": "main", "line": 15, "column": 0, "message": "Too many arguments for \"bar\"", "hint": null, "code": "call-arg"}
+{"file": "main", "line": 12, "column": 12, "message": "Revealed type is \"Overload(def (), def (x: builtins.int))\"", "hint": null, "code": "misc", "is_note": true}
+{"file": "main", "line": 14, "column": 0, "message": "No overload variant of \"foo\" matches argument type \"str\"", "hint": "Possible overload variants:\n    def foo() -> None\n    def foo(x: int) -> None", "code": "call-overload", "is_note": false}
+{"file": "main", "line": 17, "column": 0, "message": "Too many arguments for \"bar\"", "hint": null, "code": "call-arg", "is_note": false}