Make error for invalid lazy from __future__ ... import prettier

Author: StanFromIreland

Grammar/python.gram

@@ -230,7 +230,7 @@ import_name[stmt_ty]:
 # note below: the ('.' | '...') is necessary because '...' is tokenized as ELLIPSIS
 import_from[stmt_ty]:
     | lazy="lazy"? 'from' a=('.' | '...')* b=dotted_name 'import' c=import_from_targets {
-        _PyPegen_checked_future_import(p, b->v.Name.id, c, _PyPegen_seq_count_dots(a), lazy ? 1 : 0, EXTRA) }
+        _PyPegen_checked_future_import(p, b->v.Name.id, c, _PyPegen_seq_count_dots(a), lazy, EXTRA) }
     | lazy="lazy"? 'from' a=('.' | '...')+ 'import' b=import_from_targets {
         _PyAST_ImportFrom(NULL, b, _PyPegen_seq_count_dots(a), lazy ? 1 : 0, EXTRA) }
 import_from_targets[asdl_alias_seq*]:

Lib/test/test_import/test_lazy_imports.py

@@ -219,8 +219,11 @@ def test_lazy_try_except_from_star(self):
 
     def test_lazy_future_import(self):
         """lazy from __future__ import should raise SyntaxError."""
-        with self.assertRaises(SyntaxError):
+        with self.assertRaises(SyntaxError) as cm:
             import test.test_import.data.lazy_imports.lazy_future_import
+        # Check we highlight 'lazy' (column offset 0, end offset 4)
+        self.assertEqual(cm.exception.offset, 1)
+        self.assertEqual(cm.exception.end_offset, 5)
 
     def test_lazy_import_func(self):
         """lazy import inside function should raise SyntaxError."""

Parser/action_helpers.c

@@ -1943,11 +1943,11 @@ _PyPegen_concatenate_strings(Parser *p, asdl_expr_seq *strings,
 
 stmt_ty
 _PyPegen_checked_future_import(Parser *p, identifier module, asdl_alias_seq * names, int level,
-                               int is_lazy, int lineno, int col_offset, int end_lineno, int end_col_offset,
-                      		   PyArena *arena) {
+                               expr_ty lazy_token, int lineno, int col_offset, int end_lineno, int end_col_offset,
+                               PyArena *arena) {
     if (level == 0 && PyUnicode_CompareWithASCIIString(module, "__future__") == 0) {
-        if (is_lazy) {
-            RAISE_SYNTAX_ERROR("lazy from __future__ import is not allowed");
+        if (lazy_token) {
+            RAISE_SYNTAX_ERROR_KNOWN_LOCATION(lazy_token, "lazy from __future__ import is not allowed");
             return NULL;
         }
         for (Py_ssize_t i = 0; i < asdl_seq_LEN(names); i++) {
@@ -1957,7 +1957,7 @@ _PyPegen_checked_future_import(Parser *p, identifier module, asdl_alias_seq * na
             }
         }
     }
-    return _PyAST_ImportFrom(module, names, level, is_lazy, lineno, col_offset, end_lineno, end_col_offset, arena);
+    return _PyAST_ImportFrom(module, names, level, lazy_token ? 1 : 0, lineno, col_offset, end_lineno, end_col_offset, arena);
 }
 
 asdl_stmt_seq*

Parser/parser.c

@@ -366,7 +366,7 @@ void *_PyPegen_arguments_parsing_error(Parser *, expr_ty);
 expr_ty _PyPegen_get_last_comprehension_item(comprehension_ty comprehension);
 void *_PyPegen_nonparen_genexp_in_call(Parser *p, expr_ty args, asdl_comprehension_seq *comprehensions);
 stmt_ty _PyPegen_checked_future_import(Parser *p, identifier module, asdl_alias_seq *,
-                                       int , int, int , int , int , int, PyArena *);
+                                       int, expr_ty, int, int, int, int, PyArena *);
 asdl_stmt_seq* _PyPegen_register_stmts(Parser *p, asdl_stmt_seq* stmts);
 stmt_ty _PyPegen_register_stmt(Parser *p, stmt_ty s);