support displaying ast types (#125)

* support displaying ast types

* support 3.7 & 3.8

Author: samuelcolvin

devtools/prettier.py

@@ -1,3 +1,4 @@
+import ast
 import io
 import os
 from collections import OrderedDict
@@ -80,6 +81,7 @@ def __init__(
             (bytearray, self._format_bytearray),
             (generator_types, self._format_generator),
             # put these last as the check can be slow
+            (ast.AST, self._format_ast_expression),
             (LaxMapping, self._format_dict),
             (DataClassType, self._format_dataclass),
             (SQLAlchemyClassType, self._format_sqlalchemy_class),
@@ -240,6 +242,17 @@ def _format_bytearray(self, value: 'Any', _: str, indent_current: int, indent_ne
         lines = self._wrap_lines(bytes(value), indent_new)
         self._str_lines(lines, indent_current, indent_new)
 
+    def _format_ast_expression(self, value: ast.AST, _: str, indent_current: int, indent_new: int) -> None:
+        try:
+            s = ast.dump(value, indent=self._indent_step)
+        except TypeError:
+            # no indent before 3.9
+            s = ast.dump(value)
+        lines = s.splitlines(True)
+        self._stream.write(lines[0])
+        for line in lines[1:]:
+            self._stream.write(indent_current * self._c + line)
+
     def _format_dataclass(self, value: 'Any', _: str, indent_current: int, indent_new: int) -> None:
         self._format_fields(value, value.__dict__.items(), indent_current, indent_new)
 

requirements/testing.in

@@ -5,7 +5,9 @@ pytest-mock
 pytest-pretty
 # these packages are used in tests so install the latest version
 pydantic
-asyncpg
+# no binaries for 3.7
+asyncpg; python_version>='3.8'
+# no version is compatible with 3.7 and 3.11
 numpy; python_version>='3.8'
 multidict; python_version>='3.8'
 sqlalchemy

requirements/testing.txt

@@ -4,7 +4,7 @@
 #
 #    pip-compile --output-file=requirements/testing.txt --resolver=backtracking requirements/testing.in
 #
-asyncpg==0.27.0
+asyncpg==0.27.0 ; python_version >= "3.8"
     # via -r requirements/testing.in
 attrs==22.2.0
     # via pytest

tests/test_prettier.py

@@ -1,5 +1,7 @@
+import ast
 import os
 import string
+import sys
 from collections import Counter, OrderedDict, namedtuple
 from dataclasses import dataclass
 from typing import List
@@ -457,3 +459,26 @@ class User(SQLAlchemyBase):
         "    nickname='test',\n"
         ")"
     )
+
+
+@pytest.mark.skipif(sys.version_info < (3, 9), reason='no indent on older versions')
+def test_ast_expr():
+    assert pformat(ast.parse('print(1, 2, round(3))', mode='eval')) == (
+        "Expression("
+        "\n    body=Call("
+        "\n        func=Name(id='print', ctx=Load()),"
+        "\n        args=["
+        "\n            Constant(value=1),"
+        "\n            Constant(value=2),"
+        "\n            Call("
+        "\n                func=Name(id='round', ctx=Load()),"
+        "\n                args=["
+        "\n                    Constant(value=3)],"
+        "\n                keywords=[])],"
+        "\n        keywords=[]))"
+    )
+
+
+@pytest.mark.skipif(sys.version_info < (3, 9), reason='no indent on older versions')
+def test_ast_module():
+    assert pformat(ast.parse('print(1, 2, round(3))')).startswith('Module(\n    body=[')