PEP 639: Implement License-Expression and License-File

noxfile.py

@@ -181,6 +181,12 @@ def release(session):
     webbrowser.open("https://github.com/pypa/packaging/releases")
 
 
+@nox.session
+def update_licenses(session: nox.Session) -> None:
+    session.install("httpx")
+    session.run("python", "tasks/licenses.py")
+
+
 # -----------------------------------------------------------------------------
 # Helpers
 # -----------------------------------------------------------------------------

pyproject.toml

@@ -57,9 +57,11 @@ warn_unused_ignores = true
 module = ["_manylinux"]
 ignore_missing_imports = true
 
-
 [tool.ruff]
 src = ["src"]
+extend-exclude = [
+    "src/packaging/licenses/spdx.py"
+]
 
 [tool.ruff.lint]
 extend-select = [

src/packaging/licenses/__init__.py

@@ -0,0 +1,126 @@
+#######################################################################################
+#
+# Adapted from:
+#  https://github.com/pypa/hatch/blob/5352e44/backend/src/hatchling/licenses/parse.py
+#
+# MIT License
+#
+# Copyright (c) 2017-present Ofek Lev <[email protected]>
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy of this
+# software and associated documentation files (the "Software"), to deal in the Software
+# without restriction, including without limitation the rights to use, copy, modify,
+# merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
+# permit persons to whom the Software is furnished to do so, subject to the following
+# conditions:
+#
+# The above copyright notice and this permission notice shall be included in all copies
+# or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+# INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+# PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+# HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
+# CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE
+# OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+#
+#
+# With additional allowance of arbitrary `LicenseRef-` identifiers, not just
+# `LicenseRef-Public-Domain` and `LicenseRef-Proprietary`.
+#
+#######################################################################################
+from __future__ import annotations
+
+import re
+from typing import cast
+
+from packaging.licenses.spdx import EXCEPTIONS, LICENSES
+
+license_ref_allowed = re.compile("^[A-Za-z0-9.-]*$")
+
+
+def normalize_license_expression(raw_license_expression: str) -> str | None:
+    if not raw_license_expression:
+        return None
+
+    license_refs = {
+        ref.lower(): "LicenseRef-" + ref[11:]
+        for ref in raw_license_expression.split()
+        if ref.lower().startswith("licenseref-")
+    }
+
+    # First normalize to lower case so we can look up licenses/exceptions
+    # and so boolean operators are Python-compatible
+    license_expression = raw_license_expression.lower()
+
+    # Then pad parentheses so tokenization can be achieved by merely splitting on
+    # white space
+    license_expression = license_expression.replace("(", " ( ").replace(")", " ) ")
+
+    # Now we begin parsing
+    tokens = license_expression.split()
+
+    # Rather than implementing boolean logic we create an expression that Python can
+    # parse. Everything that is not involved with the grammar itself is treated as
+    # `False` and the expression should evaluate as such.
+    python_tokens = []
+    for token in tokens:
+        if token not in {"or", "and", "with", "(", ")"}:
+            python_tokens.append("False")
+        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)
+        else:
+            python_tokens.append(token)
+
+    python_expression = " ".join(python_tokens)
+    try:
+        result = eval(python_expression)
+    except Exception:
+        result = True
+
+    if result is not False:
+        message = f"invalid license expression: {raw_license_expression}"
+        raise ValueError(message) from None
+
+    # Take a final pass to check for unknown licenses/exceptions
+    normalized_tokens = []
+    for token in tokens:
+        if token in {"or", "and", "with", "(", ")"}:
+            normalized_tokens.append(token.upper())
+            continue
+
+        if normalized_tokens and normalized_tokens[-1] == "WITH":
+            if token not in EXCEPTIONS:
+                message = f"unknown license exception: {token}"
+                raise ValueError(message)
+
+            normalized_tokens.append(cast(str, EXCEPTIONS[token]["id"]))
+        else:
+            if token.endswith("+"):
+                final_token = token[:-1]
+                suffix = "+"
+            else:
+                final_token = token
+                suffix = ""
+
+            if final_token.startswith("licenseref-"):
+                if not license_ref_allowed.match(final_token):
+                    message = f"invalid licenseref: {final_token}"
+                    raise ValueError(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)
+                normalized_tokens.append(
+                    cast(str, LICENSES[final_token]["id"]) + suffix
+                )
+
+    # Construct the normalized expression
+    normalized_expression = " ".join(normalized_tokens)
+
+    # Fix internal padding for parentheses
+    return normalized_expression.replace("( ", "(").replace(" )", ")")