add support for printing the diff of AST trees when running tests (#3902)

[etc/vim.git] / tests / util.py

diff --git a/tests/util.py b/tests/util.py
index d65c2e651ae9552c6670ad8964d79b821e10d285..541d21da4dfd9dddb1168cfdd18b2ce10e8f023b 100644 (file)
--- a/tests/util.py
+++ b/tests/util.py
@@ -2,6 +2,7 @@ import os
 import sys
 import unittest
 from contextlib import contextmanager
+from dataclasses import replace
 from functools import partial
 from pathlib import Path
 from typing import Any, Iterator, List, Optional, Tuple
@@ -11,6 +12,8 @@ from black.debug import DebugVisitor
 from black.mode import TargetVersion
 from black.output import diff, err, out
 
+from . import conftest
+
 PYTHON_SUFFIX = ".py"
 ALLOWED_SUFFIXES = (PYTHON_SUFFIX, ".pyi", ".out", ".diff", ".ipynb")
 
@@ -33,22 +36,34 @@ fs = partial(black.format_str, mode=DEFAULT_MODE)
 
 
 def _assert_format_equal(expected: str, actual: str) -> None:
-    if actual != expected and not os.environ.get("SKIP_AST_PRINT"):
+    if actual != expected and (conftest.PRINT_FULL_TREE or conftest.PRINT_TREE_DIFF):
         bdv: DebugVisitor[Any]
-        out("Expected tree:", fg="green")
+        actual_out: str = ""
+        expected_out: str = ""
+        if conftest.PRINT_FULL_TREE:
+            out("Expected tree:", fg="green")
         try:
             exp_node = black.lib2to3_parse(expected)
-            bdv = DebugVisitor()
+            bdv = DebugVisitor(print_output=conftest.PRINT_FULL_TREE)
             list(bdv.visit(exp_node))
+            expected_out = "\n".join(bdv.list_output)
         except Exception as ve:
             err(str(ve))
-        out("Actual tree:", fg="red")
+        if conftest.PRINT_FULL_TREE:
+            out("Actual tree:", fg="red")
         try:
             exp_node = black.lib2to3_parse(actual)
-            bdv = DebugVisitor()
+            bdv = DebugVisitor(print_output=conftest.PRINT_FULL_TREE)
             list(bdv.visit(exp_node))
+            actual_out = "\n".join(bdv.list_output)
         except Exception as ve:
             err(str(ve))
+        if conftest.PRINT_TREE_DIFF:
+            out("Tree Diff:")
+            out(
+                diff(expected_out, actual_out, "expected tree", "actual tree")
+                or "Trees do not differ"
+            )
 
     if actual != expected:
         out(diff(expected, actual, "expected", "actual"))
@@ -56,6 +71,10 @@ def _assert_format_equal(expected: str, actual: str) -> None:
     assert actual == expected
 
 
+class FormatFailure(Exception):
+    """Used to wrap failures when assert_format() runs in an extra mode."""
+
+
 def assert_format(
     source: str,
     expected: str,
@@ -70,12 +89,57 @@ def assert_format(
     safety guards so they don't just crash with a SyntaxError. Please note this is
     separate from TargetVerson Mode configuration.
     """
+    _assert_format_inner(
+        source, expected, mode, fast=fast, minimum_version=minimum_version
+    )
+
+    # For both preview and non-preview tests, ensure that Black doesn't crash on
+    # this code, but don't pass "expected" because the precise output may differ.
+    try:
+        _assert_format_inner(
+            source,
+            None,
+            replace(mode, preview=not mode.preview),
+            fast=fast,
+            minimum_version=minimum_version,
+        )
+    except Exception as e:
+        text = "non-preview" if mode.preview else "preview"
+        raise FormatFailure(
+            f"Black crashed formatting this case in {text} mode."
+        ) from e
+    # Similarly, setting line length to 1 is a good way to catch
+    # stability bugs. But only in non-preview mode because preview mode
+    # currently has a lot of line length 1 bugs.
+    try:
+        _assert_format_inner(
+            source,
+            None,
+            replace(mode, preview=False, line_length=1),
+            fast=fast,
+            minimum_version=minimum_version,
+        )
+    except Exception as e:
+        raise FormatFailure(
+            "Black crashed formatting this case with line-length set to 1."
+        ) from e
+
+
+def _assert_format_inner(
+    source: str,
+    expected: Optional[str] = None,
+    mode: black.Mode = DEFAULT_MODE,
+    *,
+    fast: bool = False,
+    minimum_version: Optional[Tuple[int, int]] = None,
+) -> None:
     actual = black.format_str(source, mode=mode)
-    _assert_format_equal(expected, actual)
+    if expected is not None:
+        _assert_format_equal(expected, actual)
     # It's not useful to run safety checks if we're expecting no changes anyway. The
     # assertion right above will raise if reality does actually make changes. This just
     # avoids wasted CPU cycles.
-    if not fast and source != expected:
+    if not fast and source != actual:
         # Unfortunately the AST equivalence check relies on the built-in ast module
         # being able to parse the code being formatted. This doesn't always work out
         # when checking modern code on older versions.