inspection: improve package info error message

poetry/inspection/info.py

@@ -43,9 +43,14 @@
 
 
 class PackageInfoError(ValueError):
- def __init__(self, path): # type: (Union[Path, str]) -> None
+ def __init__(
+ self, path, *reasons
+ ): # type: (Union[Path, str], *Union[BaseException, str]) -> None
+ reasons = (
+ "Unable to determine package info for path: {}".format(str(path)),
+ ) + reasons
  super(PackageInfoError, self).__init__(
- "Unable to determine package info for path: {}".format(str(path))
+ "\n\n".join(str(msg).strip() for msg in reasons if msg)
  )
 
 
@@ -290,12 +295,14 @@ def from_setup_files(cls, path): # type: (Path) -> PackageInfo
  :param path: Path to `setup.py` file
  """
  if not cls.has_setup_files(path):
- raise PackageInfoError(path)
+ raise PackageInfoError(
+ path, "No setup files (setup.py, setup.cfg) was found."
+ )
 
  try:
  result = SetupReader.read_from_directory(path)
- except Exception:
- raise PackageInfoError(path)
+ except Exception as e:
+ raise PackageInfoError(path, e)
 
  python_requires = result["python_requires"]
  if python_requires is None:
@@ -328,7 +335,10 @@ def from_setup_files(cls, path): # type: (Path) -> PackageInfo
 
  if not (info.name and info.version) and not info.requires_dist:
  # there is nothing useful here
- raise PackageInfoError(path)
+ raise PackageInfoError(
+ path,
+ "No core metadata (name, version, requires-dist) could be retrieved.",
+ )
 
  return info
 
@@ -474,15 +484,21 @@ def _pep517_metadata(cls, path): # type (Path) -> PackageInfo
  cls._log("PEP517 build failed: {}".format(e), level="debug")
  setup_py = path / "setup.py"
  if not setup_py.exists():
- raise PackageInfoError(path)
+ raise PackageInfoError(
+ path,
+ e,
+ "No fallback setup.py file was found to generate egg_info.",
+ )
 
  cwd = Path.cwd()
  os.chdir(path.as_posix())
  try:
  venv.run("python", "setup.py", "egg_info")
  return cls.from_metadata(path)
- except EnvCommandError:
- raise PackageInfoError(path)
+ except EnvCommandError as fbe:
+ raise PackageInfoError(
+ path, "Fallback egg_info generation failed.", fbe
+ )
  finally:
  os.chdir(cwd.as_posix())
 
@@ -493,7 +509,7 @@ def _pep517_metadata(cls, path): # type (Path) -> PackageInfo
  return info
 
  # if we reach here, everything has failed and all hope is lost
- raise PackageInfoError(path)
+ raise PackageInfoError(path, "Exhausted all core metadata sources.")
 
  @classmethod
  def from_directory(
@@ -572,8 +588,8 @@ def from_bdist(cls, path): # type: (Path) -> PackageInfo
 
  try:
  return cls._from_distribution(pkginfo.BDist(str(path)))
- except ValueError:
- raise PackageInfoError(path)
+ except ValueError as e:
+ raise PackageInfoError(path, e)
 
  @classmethod
  def from_path(cls, path): # type: (Path) -> PackageInfo