Make print_ast() break arguments over multiple lines

Replicates graphql/graphql-js@b9cf5f3

Author: Cito

src/graphql/language/printer.py

@@ -9,6 +9,8 @@
 __all__ = ["print_ast"]
 
 
+MAX_LINE_LENGTH = 80
+
 Strings = Collection[str]
 
 
@@ -100,16 +102,13 @@ def leave_selection_set(node: PrintedNode, *_args: Any) -> str:
 
     @staticmethod
     def leave_field(node: PrintedNode, *_args: Any) -> str:
-        return join(
-            (
-                wrap("", node.alias, ": ")
-                + node.name
-                + wrap("(", join(node.arguments, ", "), ")"),
-                join(node.directives, " "),
-                node.selection_set,
-            ),
-            " ",
-        )
+        prefix = wrap("", node.alias, ": ") + node.name
+        args_line = prefix + wrap("(", join(node.arguments, ", "), ")")
+
+        if len(args_line) > MAX_LINE_LENGTH:
+            args_line = prefix + wrap("(\n", indent(join(node.arguments, "\n")), "\n)")
+
+        return join((args_line, join(node.directives, " "), node.selection_set), " ")
 
     @staticmethod
     def leave_argument(node: PrintedNode, *_args: Any) -> str:

tests/language/test_printer.py

@@ -78,6 +78,42 @@ def prints_query_with_variable_directives():
             """
         )
 
+    def keeps_arguments_on_one_line_if_line_has_80_chars_or_less():
+        printed = print_ast(parse("{trip(wheelchair:false arriveBy:false){dateTime}}"))
+
+        assert printed == dedent(
+            """
+            {
+              trip(wheelchair: false, arriveBy: false) {
+                dateTime
+              }
+            }
+            """
+        )
+
+    def puts_arguments_on_multiple_lines_if_line_has_more_than_80_chars():
+        printed = print_ast(
+            parse(
+                "{trip(wheelchair:false arriveBy:false includePlannedCancellations:true"
+                " transitDistanceReluctance:2000){dateTime}}"
+            )
+        )
+
+        assert printed == dedent(
+            """
+            {
+              trip(
+                wheelchair: false
+                arriveBy: false
+                includePlannedCancellations: true
+                transitDistanceReluctance: 2000
+              ) {
+                dateTime
+              }
+            }
+            """
+        )
+
     def experimental_prints_fragment_with_variable_directives():
         query_ast_with_variable_directive = parse(
             "fragment Foo($foo: TestType @test) on TestType @testDirective { id }",
@@ -149,9 +185,13 @@ def prints_kitchen_sink(kitchen_sink_query):  # noqa: F811
             }
 
             fragment frag on Friend @onFragmentDefinition {
-              foo(size: $size, bar: $b, obj: {key: "value", block: """
-                block string uses \"""
-              """})
+              foo(
+                size: $size
+                bar: $b
+                obj: {key: "value", block: """
+                  block string uses \"""
+                """}
+              )
             }
 
             {