Fix line counting in get_location and print_block_string

src/graphql/language/block_string.py

@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+import re
 from sys import maxsize
 from typing import TYPE_CHECKING
 
@@ -14,6 +15,8 @@
     "print_block_string",
 ]
 
+_re_newline = re.compile(r"\r\n|[\n\r]")
+
 
 def dedent_block_string_lines(lines: Collection[str]) -> list[str]:
     """Produce the value of a block string from its parsed raw value.
@@ -120,8 +123,10 @@ def print_block_string(value: str, minimize: bool = False) -> str:
 
     escaped_value = value.replace('"""', '\\"""')
 
-    # Expand a block string's raw value into independent lines.
-    lines = escaped_value.splitlines() or [""]
+    # Expand a block string's raw value into independent lines. Split on the
+    # GraphQL line terminators only (LF, CR, CRLF) like graphql-js; Python's
+    # str.splitlines() would also split on characters like VT, FF and NEL.
+    lines = _re_newline.split(escaped_value) or [""]
     num_lines = len(lines)
     is_single_line = num_lines == 1
 

src/graphql/language/source.py

@@ -2,12 +2,15 @@
 
 from __future__ import annotations
 
+import re
 from typing import Any, TypeGuard
 
 from .location import SourceLocation
 
 __all__ = ["Source", "is_source"]
 
+_re_newline = re.compile(r"\r\n|[\n\r]")
+
 DEFAULT_NAME = "GraphQL request"
 DEFAULT_SOURCE_LOCATION = SourceLocation(1, 1)
 
@@ -87,13 +90,14 @@ def get_location(self, position: int) -> SourceLocation:
         >>> Source('type Query {\n  hello: String\n}').get_location(15)
         SourceLocation(line=2, column=3)
         """
-        lines = self.body[:position].splitlines()
-        if lines:
-            line = len(lines)
-            column = len(lines[-1]) + 1
-        else:
-            line = 1
-            column = 1
+        # Split only on GraphQL line terminators (LF, CR and CRLF), which is
+        # how graphql-js and print_source_location() count lines. Python's
+        # str.splitlines() also splits on characters like VT, FF, NEL and
+        # U+2028/U+2029, and drops a trailing empty line, which produced both
+        # wrong locations and crashes when printing error locations.
+        lines = _re_newline.split(self.body[:position])
+        line = len(lines)
+        column = len(lines[-1]) + 1
         return SourceLocation(line, column)
 
     def __repr__(self) -> str:

tests/error/test_print_location.py

@@ -79,3 +79,17 @@ def prints_line_numbers_with_correct_padding():
             10 |
             """
         )
+
+    def prints_locations_from_get_location_on_non_graphql_line_breaks():
+        # Characters like VT, FF, NEL or U+2028/U+2029 are not GraphQL line
+        # terminators, so Source.get_location() reports line 1 for positions
+        # after them. Rendering that location must not fail.
+        source = Source("x\vy")
+        result = print_source_location(source, source.get_location(3))
+        assert result == dedent(
+            """
+            GraphQL request:1:4
+            1 | x\x0by
+              |    ^
+            """
+        )

tests/language/test_block_string.py

@@ -216,3 +216,9 @@ def __str__(self) -> str:
                 return "lazy"
 
         _assert_block_string(cast("str", LazyString()), '"""lazy"""')
+
+    def treats_non_graphql_line_breaks_as_single_line():
+        # VT, FF, NEL and U+2028/U+2029 are not GraphQL line terminators, so
+        # values containing them print as a single line (graphql-js parity).
+        for char in "\v\f\x85\u2028\u2029":
+            _assert_block_string(f"a{char}b", f'"""a{char}b"""')

tests/language/test_source.py

@@ -46,6 +46,18 @@ def can_get_location():
         assert isinstance(location, SourceLocation)
         assert location == (2, 6)
 
+    def counts_only_graphql_line_terminators_for_locations():
+        # Positions right after a line terminator are on the next line.
+        assert Source("a\nb").get_location(2) == (2, 1)
+        assert Source("a\rb").get_location(2) == (2, 1)
+        assert Source("a\r\nb").get_location(3) == (2, 1)
+        # Characters that splitlines() counts as line boundaries, but which
+        # are not GraphQL line terminators, stay on the same line (graphql-js
+        # parity).
+        for char in "\v\f\x1c\x1d\x1e\x85\u2028\u2029":
+            source = Source(f"x{char}y")
+            assert source.get_location(3) == (1, 4)
+
     def can_be_stringified():
         source = Source("")
         assert str(source) == "<Source name='GraphQL request'>"