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#!/usr/bin/env nix-shell
#!nix-shell -i python -p python3 swiftPackages.swift-unwrapped
"""
Generate a frameworks.nix for a macOS SDK.
You may point this tool at an Xcode bundled SDK, but more ideal is using the
SDK from Nixpkgs. For example:
SDK_PATH="$(nix-build --no-link -A darwin.apple_sdk_11_0.MacOSX-SDK)"
./gen-frameworks.py "$SDK_PATH" > ./new-frameworks.nix
"""
import json
import os
import subprocess
import sys
ALLOWED_LIBS = ["simd"]
HEADER = """\
# This file is generated by gen-frameworks.nix.
# Do not edit, put overrides in apple_sdk.nix instead.
{ libs, frameworks }: with libs; with frameworks;
{
"""
FOOTER = """\
}
"""
def eprint(*args):
print(*args, file=sys.stderr)
def name_from_ident(ident):
return ident.get("swift", ident.get("clang"))
def scan_sdk(sdk):
# Find frameworks by scanning the SDK frameworks directory.
frameworks = [
framework.removesuffix(".framework")
for framework in os.listdir(f"{sdk}/System/Library/Frameworks")
if not framework.startswith("_")
]
frameworks.sort()
# Determine the longest name for padding output.
width = len(max(frameworks, key=len))
output = HEADER
for framework in frameworks:
deps = []
# Use Swift to scan dependencies, because a module may have both Clang
# and Swift parts. Using Clang only imports the Clang module, whereas
# using Swift will usually import both Clang + Swift overlay.
#
# TODO: The above is an assumption. Not sure if it's possible a Swift
# module completely shadows a Clang module. (Seems unlikely)
#
# TODO: Handle "module 'Foobar' is incompatible with feature 'swift'"
#
# If there were a similar Clang invocation for scanning, we could fix
# the above todos, but that doesn't appear to exist.
eprint(f"# scanning {framework}")
result = subprocess.run(
[
"swiftc",
"-scan-dependencies",
# We provide a source snippet via stdin.
"-",
# Use the provided SDK.
"-sdk",
sdk,
# This search path is normally added automatically by the
# compiler based on the SDK, but we have a patch in place that
# removes that for SDKs in /nix/store, because our xcbuild stub
# SDK doesn't have the directory.
# (swift-prevent-sdk-dirs-warning.patch)
"-I",
f"{sdk}/usr/lib/swift",
# For some reason, 'lib/swift/shims' from both the SDK and
# Swift compiler are picked up, causing redefinition errors.
# This eliminates the latter.
"-resource-dir",
f"{sdk}/usr/lib/swift",
],
input=f"import {framework}".encode(),
stdout=subprocess.PIPE,
)
if result.returncode != 0:
eprint(f"# Scanning {framework} failed (exit code {result.returncode})")
result.stdout = b""
# Parse JSON output.
if len(result.stdout) != 0:
data = json.loads(result.stdout)
# Entries in the modules list come in pairs. The first is an
# identifier (`{ swift: "foobar" }` or `{ clang: "foobar" }`), and
# the second metadata for that module. Here we look for the pair
# that matches the framework we're scanning (and ignore the rest).
modules = data["modules"]
for i in range(0, len(modules), 2):
ident, meta = modules[i : i + 2]
# NOTE: We may match twice, for a Swift module _and_ for a
# Clang module. So matching here doesn't break from the loop,
# and deps is appended to.
if name_from_ident(ident) == framework:
dep_idents = meta["directDependencies"]
deps += [name_from_ident(ident) for ident in dep_idents]
# List unfiltered deps in progress output.
eprint(ident, "->", dep_idents)
# Filter out modules that are not separate derivations.
# Also filter out duplicates (when a Swift overlay imports the Clang module)
allowed = frameworks + ALLOWED_LIBS
deps = set([dep for dep in deps if dep in allowed])
# Filter out self-references. (Swift overlay importing Clang module.)
if framework in deps:
deps.remove(framework)
# Generate a Nix attribute line.
if len(deps) != 0:
deps = list(deps)
deps.sort()
deps = " ".join(deps)
output += f" {framework.ljust(width)} = {{ inherit {deps}; }};\n"
else:
output += f" {framework.ljust(width)} = {{}};\n"
output += FOOTER
sys.stdout.write(output)
if __name__ == "__main__":
if len(sys.argv) != 2:
eprint(f"Usage: {sys.argv[0]} <path to MacOSX.sdk>")
sys.exit(64)
scan_sdk(sys.argv[1])
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