subclass ValueError for invalid license expressions

src/packaging/licenses/__init__.py

@@ -38,6 +38,16 @@
 license_ref_allowed = re.compile("^[A-Za-z0-9.-]*$")
 
 
+class InvalidLicenseExpression(ValueError):
+ """Raised when a license-expression string
+
+ >>> normalize_license_expression("invalid")
+ Traceback (most recent call last):
+ ...
+ packaging.licenses.InvalidLicenseExpression: Invalid license expression: 'invalid'
+ """
+
+
 def normalize_license_expression(raw_license_expression: str) -> str | None:
  if not raw_license_expression:
  return None
@@ -68,8 +78,8 @@ def normalize_license_expression(raw_license_expression: str) -> str | None:
  elif token == "with":
  python_tokens.append("or")
  elif token == "(" and python_tokens and python_tokens[-1] not in {"or", "and"}:
- message = f"invalid license expression: {raw_license_expression}"
- raise ValueError(message)
+ message = f"Invalid license expression: {raw_license_expression}"
+ raise InvalidLicenseExpression(message)
  else:
  python_tokens.append(token)
 
@@ -80,8 +90,8 @@ def normalize_license_expression(raw_license_expression: str) -> str | None:
  result = True
 
  if result is not False:
- message = f"invalid license expression: {raw_license_expression}"
- raise ValueError(message) from None
+ message = f"Invalid license expression: {raw_license_expression}"
+ raise InvalidLicenseExpression(message) from None
 
  # Take a final pass to check for unknown licenses/exceptions.
  normalized_tokens = []
@@ -92,8 +102,8 @@ def normalize_license_expression(raw_license_expression: str) -> str | None:
 
  if normalized_tokens and normalized_tokens[-1] == "WITH":
  if token not in EXCEPTIONS:
- message = f"unknown license exception: {token}"
- raise ValueError(message)
+ message = f"Unknown license exception: {token}"
+ raise InvalidLicenseExpression(message)
 
  normalized_tokens.append(EXCEPTIONS[token]["id"])
  else:
@@ -106,13 +116,13 @@ def normalize_license_expression(raw_license_expression: str) -> str | None:
 
  if final_token.startswith("licenseref-"):
  if not license_ref_allowed.match(final_token):
- message = f"invalid licenseref: {final_token}"
- raise ValueError(message)
+ message = f"Invalid licenseref: {final_token}"
+ raise InvalidLicenseExpression(message)
  normalized_tokens.append(license_refs[final_token] + suffix)
  else:
  if final_token not in LICENSES:
- message = f"unknown license: {final_token}"
- raise ValueError(message)
+ message = f"Unknown license: {final_token}"
+ raise InvalidLicenseExpression(message)
  normalized_tokens.append(LICENSES[final_token]["id"] + suffix)
 
  normalized_expression = " ".join(normalized_tokens)