Improve pyproject.toml validation messages (#3487)

changelog.d/3487.misc.rst

@@ -0,0 +1,2 @@
+Modified ``pyproject.toml`` validation exception handling to
+make relevant debugging information easier to spot.

setuptools/config/pyprojecttoml.py

@@ -41,10 +41,14 @@ def validate(config: dict, filepath: _Path) -> bool:
     try:
         return validator.validate(config)
     except validator.ValidationError as ex:
-        _logger.error(f"configuration error: {ex.summary}")  # type: ignore
-        _logger.debug(ex.details)  # type: ignore
-        error = ValueError(f"invalid pyproject.toml config: {ex.name}")  # type: ignore
-        raise error from None
+        summary = f"configuration error: {ex.summary}"
+        if ex.name.strip("`") != "project":
+            # Probably it is just a field missing/misnamed, not worthy the verbosity...
+            _logger.debug(summary)
+            _logger.debug(ex.details)
+
+        error = f"invalid pyproject.toml config: {ex.name}."
+        raise ValueError(f"{error}\n{summary}") from None
 
 
 def apply_configuration(

setuptools/tests/config/test_pyprojecttoml.py

@@ -1,4 +1,3 @@
-import logging
 import re
 from configparser import ConfigParser
 from inspect import cleandoc
@@ -307,7 +306,7 @@ def test_ignore_unrelated_config(tmp_path, example):
 
 
 @pytest.mark.parametrize(
-    "example, error_msg, value_shown_in_debug",
+    "example, error_msg",
     [
         (
             """
@@ -316,30 +315,18 @@ def test_ignore_unrelated_config(tmp_path, example):
             version = "1.2"
             requires = ['pywin32; platform_system=="Windows"' ]
             """,
-            "configuration error: `project` must not contain {'requires'} properties",
-            '"requires": ["pywin32; platform_system==\\"Windows\\""]',
+            "configuration error: .project. must not contain ..requires.. properties",
         ),
     ],
 )
-def test_invalid_example(tmp_path, caplog, example, error_msg, value_shown_in_debug):
-    caplog.set_level(logging.DEBUG)
+def test_invalid_example(tmp_path, example, error_msg):
     pyproject = tmp_path / "pyproject.toml"
     pyproject.write_text(cleandoc(example))
 
-    caplog.clear()
-    with pytest.raises(ValueError, match="invalid pyproject.toml"):
+    pattern = re.compile(f"invalid pyproject.toml.*{error_msg}.*", re.M | re.S)
+    with pytest.raises(ValueError, match=pattern):
         read_configuration(pyproject)
 
-    # Make sure the logs give guidance to the user
-    error_log = caplog.record_tuples[0]
-    assert error_log[1] == logging.ERROR
-    assert error_msg in error_log[2]
-
-    debug_log = caplog.record_tuples[1]
-    assert debug_log[1] == logging.DEBUG
-    debug_msg = "".join(line.strip() for line in debug_log[2].splitlines())
-    assert value_shown_in_debug in debug_msg
-
 
 @pytest.mark.parametrize("config", ("", "[tool.something]\nvalue = 42"))
 def test_empty(tmp_path, config):