Extract print_location & print_source_location functions

Replicates graphql/graphql-js@a9a21f3

Author: Cito

README.md

@@ -13,7 +13,7 @@ a query language for APIs created by Facebook.
 [![Code Style](https://img.shields.io/badge/code%20style-black-000000.svg)](https://github.com/ambv/black)
 
 The current version 1.0.5 of GraphQL-core-next is up-to-date with GraphQL.js version
-14.3.1. All parts of the API are covered by an extensive test suite of currently 1879
+14.3.1. All parts of the API are covered by an extensive test suite of currently 1880
 unit tests.
 
 

docs/modules/error.rst

@@ -10,8 +10,8 @@ Error
 
 .. autoexception:: GraphQLSyntaxError
 
+.. autofunction:: format_error
 .. autofunction:: located_error
 .. autofunction:: print_error
-.. autofunction:: format_error
 
 .. autodata:: INVALID

docs/modules/language.rst

@@ -77,7 +77,7 @@ Location
 
 .. autofunction:: get_location
 .. autoclass:: SourceLocation
-
+.. autofunction:: print_location
 
 Parser
 ------
@@ -90,6 +90,7 @@ Source
 ------
 
 .. autoclass:: Source
+.. autofunction:: print_source_location
 
 Visitor
 -------

graphql/__init__.py

@@ -164,6 +164,9 @@
 from .language import (
     Source,
     get_location,
+    # Print source location
+    print_location,
+    print_source_location,
     # Lex
     Lexer,
     TokenKind,
@@ -500,6 +503,8 @@
     "GraphQLTypeResolver",
     "Source",
     "get_location",
+    "print_location",
+    "print_source_location",
     "Lexer",
     "TokenKind",
     "parse",

graphql/error/__init__.py

@@ -4,14 +4,12 @@
 errors.
 """
 
-from .graphql_error import GraphQLError
+from .graphql_error import GraphQLError, print_error
 
 from .syntax_error import GraphQLSyntaxError
 
 from .located_error import located_error
 
-from .print_error import print_error
-
 from .format_error import format_error
 
 from .invalid import INVALID, InvalidType
@@ -22,6 +20,6 @@
     "GraphQLError",
     "GraphQLSyntaxError",
     "format_error",
-    "print_error",
     "located_error",
+    "print_error",
 ]

graphql/error/graphql_error.py

@@ -2,14 +2,13 @@
 from typing import Any, Dict, List, Optional, Sequence, Union, TYPE_CHECKING
 
 from .format_error import format_error
-from .print_error import print_error
 
 if TYPE_CHECKING:  # pragma: no cover
     from ..language.ast import Node  # noqa: F401
     from ..language.location import SourceLocation  # noqa: F401
     from ..language.source import Source  # noqa: F401
 
-__all__ = ["GraphQLError"]
+__all__ = ["GraphQLError", "print_error"]
 
 
 class GraphQLError(Exception):
@@ -176,3 +175,25 @@ def __ne__(self, other):
     def formatted(self):
         """Get error formatted according to the specification."""
         return format_error(self)
+
+
+def print_error(error: GraphQLError) -> str:
+    """Print a GraphQLError to a string.
+
+    Represents useful location information about the error's position in the source.
+    """
+    # Lazy import to avoid a cyclic dependency between error and language
+    from ..language.print_location import print_location, print_source_location
+
+    output = [error.message]
+
+    if error.nodes:
+        for node in error.nodes:
+            if node.loc:
+                output.append(print_location(node.loc))
+    elif error.source and error.locations:
+        source = error.source
+        for location in error.locations:
+            output.append(print_source_location(source, location))
+
+    return "\n\n".join(output)

graphql/error/print_error.py

@@ -8,6 +8,8 @@
 
 from .location import get_location, SourceLocation
 
+from .print_location import print_location, print_source_location
+
 from .token_kind import TokenKind
 
 from .lexer import Lexer
@@ -102,6 +104,8 @@
 __all__ = [
     "get_location",
     "SourceLocation",
+    "print_location",
+    "print_source_location",
     "TokenKind",
     "Lexer",
     "parse",

graphql/language/__init__.py

@@ -0,0 +1,59 @@
+import re
+from functools import reduce
+from typing import List, Optional, Tuple
+
+from .ast import Location
+from .location import SourceLocation, get_location
+from .source import Source
+
+
+__all__ = ["print_location", "print_source_location"]
+
+
+def print_location(location: Location) -> str:
+    """Render a helpful description of the location in the GraphQL Source document."""
+    return print_source_location(
+        location.source, get_location(location.source, location.start)
+    )
+
+
+_re_newline = re.compile(r"\r\n|[\n\r]")
+
+
+def print_source_location(source: Source, source_location: SourceLocation) -> str:
+    """Render a helpful description of the location in the GraphQL Source document."""
+    first_line_column_offset = source.location_offset.column - 1
+    body = " " * first_line_column_offset + source.body
+
+    line_index = source_location.line - 1
+    line_offset = source.location_offset.line - 1
+    line_num = source_location.line + line_offset
+
+    column_offset = first_line_column_offset if source_location.line == 1 else 0
+    column_num = source_location.column + column_offset
+
+    lines = _re_newline.split(body)  # works a bit different from splitlines()
+    len_lines = len(lines)
+
+    def get_line(index: int) -> Optional[str]:
+        return lines[index] if 0 <= index < len_lines else None
+
+    return f"{source.name}:{line_num}:{column_num}\n" + print_prefixed_lines(
+        [
+            (f"{line_num - 1}: ", get_line(line_index - 1)),
+            (f"{line_num}: ", get_line(line_index)),
+            ("", " " * (column_num - 1) + "^"),
+            (f"{line_num + 1}: ", get_line(line_index + 1)),
+        ]
+    )
+
+
+def print_prefixed_lines(lines: List[Tuple[str, Optional[str]]]) -> str:
+    """Print lines specified like this: ["prefix", "string"]"""
+    existing_lines = [line for line in lines if line[1] is not None]
+    pad_len = reduce(lambda pad, line: max(pad, len(line[0])), existing_lines, 0)
+    return "\n".join(
+        map(
+            lambda line: line[0].rjust(pad_len) + line[1], existing_lines  # type:ignore
+        )
+    )

graphql/language/print_location.py

@@ -1,7 +1,12 @@
 from typing import cast
 
-from graphql.error import GraphQLError, format_error
-from graphql.language import parse, OperationDefinitionNode, Source
+from graphql.error import GraphQLError, format_error, print_error
+from graphql.language import (
+    parse,
+    OperationDefinitionNode,
+    ObjectTypeDefinitionNode,
+    Source,
+)
 from graphql.pyutils import dedent
 
 
@@ -134,3 +139,74 @@ def hashes_are_unique_per_instance():
         e1 = GraphQLError("msg")
         e2 = GraphQLError("msg")
         assert hash(e1) != hash(e2)
+
+
+def describe_print_error():
+    def prints_an_error_without_location():
+        error = GraphQLError("Error without location")
+        assert print_error(error) == "Error without location"
+
+    def prints_an_error_using_node_without_location():
+        error = GraphQLError(
+            "Error attached to node without location",
+            parse("{ foo }", no_location=True),
+        )
+        assert print_error(error) == "Error attached to node without location"
+
+    def prints_an_error_with_nodes_from_different_sources():
+        doc_a = parse(
+            Source(
+                dedent(
+                    """
+                    type Foo {
+                      field: String
+                    }
+                    """
+                ),
+                "SourceA",
+            )
+        )
+        op_a = doc_a.definitions[0]
+        op_a = cast(ObjectTypeDefinitionNode, op_a)
+        assert op_a and op_a.kind == "object_type_definition" and op_a.fields
+        field_a = op_a.fields[0]
+        doc_b = parse(
+            Source(
+                dedent(
+                    """
+                    type Foo {
+                      field: Int
+                    }
+                    """
+                ),
+                "SourceB",
+            )
+        )
+        op_b = doc_b.definitions[0]
+        op_b = cast(ObjectTypeDefinitionNode, op_b)
+        assert op_b and op_b.kind == "object_type_definition" and op_b.fields
+        field_b = op_b.fields[0]
+
+        error = GraphQLError(
+            "Example error with two nodes", [field_a.type, field_b.type]
+        )
+
+        printed_error = print_error(error)
+        assert printed_error + "\n" == dedent(
+            """
+            Example error with two nodes
+
+            SourceA:2:10
+            1: type Foo {
+            2:   field: String
+                        ^
+            3: }
+
+            SourceB:2:10
+            1: type Foo {
+            2:   field: Int
+                        ^
+            3: }
+            """
+        )
+        assert str(error) == printed_error