test: Use permissions from git in lint-files.py

Instead of using permissions from the local file system, which might
depend on the umask, directly check the permissions from git's metadata.

test/lint/lint-files.py

@@ -11,29 +11,36 @@
 import re
 import sys
 from subprocess import check_output
-from typing import Optional, NoReturn
+from typing import Dict, Optional, NoReturn
 
 CMD_TOP_LEVEL = ["git", "rev-parse", "--show-toplevel"]
-CMD_ALL_FILES = ["git", "ls-files", "-z", "--full-name"]
-CMD_SOURCE_FILES = ["git", "ls-files", "-z", "--full-name", "--", "*.[cC][pP][pP]", "*.[hH]", "*.[pP][yY]", "*.[sS][hH]"]
+CMD_ALL_FILES = ["git", "ls-files", "-z", "--full-name", "--stage"]
 CMD_SHEBANG_FILES = ["git", "grep", "--full-name", "--line-number", "-I", "^#!"]
 
+ALL_SOURCE_FILENAMES_REGEXP = r"^.*\.(cpp|h|py|sh)$"
 ALLOWED_FILENAME_REGEXP = "^[a-zA-Z0-9/_.@][a-zA-Z0-9/_.@-]*$"
 ALLOWED_SOURCE_FILENAME_REGEXP = "^[a-z0-9_./-]+$"
 ALLOWED_SOURCE_FILENAME_EXCEPTION_REGEXP = (
     "^src/(secp256k1/|minisketch/|univalue/|test/fuzz/FuzzedDataProvider.h)"
 )
-ALLOWED_PERMISSION_NON_EXECUTABLES = 644
-ALLOWED_PERMISSION_EXECUTABLES = 755
+ALLOWED_PERMISSION_NON_EXECUTABLES = 0o644
+ALLOWED_PERMISSION_EXECUTABLES = 0o755
 ALLOWED_EXECUTABLE_SHEBANG = {
     "py": [b"#!/usr/bin/env python3"],
     "sh": [b"#!/usr/bin/env bash", b"#!/bin/sh"],
 }
 
 
 class FileMeta(object):
-    def __init__(self, file_path: str):
-        self.file_path = file_path
+    def __init__(self, file_spec: str):
+        '''Parse a `git ls files --stage` output line.'''
+        # 100755 5a150d5f8031fcd75e80a4dd9843afa33655f579 0       ci/test/00_setup_env.sh
+        meta, self.file_path = file_spec.split('\t', 2)
+        meta = meta.split()
+        # The octal file permission of the file. Internally, git only
+        # keeps an 'executable' bit, so this will always be 0o644 or 0o755.
+        self.permissions = int(meta[0], 8) & 0o7777
+        # We don't currently care about the other fields
 
     @property
     def extension(self) -> Optional[str]:
@@ -61,20 +68,24 @@ def full_extension(self) -> Optional[str]:
         except IndexError:
             return None
 
-    @property
-    def permissions(self) -> int:
-        """
-        Returns the octal file permission of the file
-        """
-        return int(oct(os.stat(self.file_path).st_mode)[-3:])
 
+def get_git_file_metadata() -> Dict[str, FileMeta]:
+    '''
+    Return a dictionary mapping the name of all files in the repository to git tree metadata.
+    '''
+    files_raw = check_output(CMD_ALL_FILES).decode("utf8").rstrip("\0").split("\0")
+    files = {}
+    for file_spec in files_raw:
+        meta = FileMeta(file_spec)
+        files[meta.file_path] = meta
+    return files
 
-def check_all_filenames() -> int:
+def check_all_filenames(files) -> int:
     """
     Checks every file in the repository against an allowed regexp to make sure only lowercase or uppercase
     alphanumerics (a-zA-Z0-9), underscores (_), hyphens (-), at (@) and dots (.) are used in repository filenames.
     """
-    filenames = check_output(CMD_ALL_FILES).decode("utf8").rstrip("\0").split("\0")
+    filenames = files.keys()
     filename_regex = re.compile(ALLOWED_FILENAME_REGEXP)
     failed_tests = 0
     for filename in filenames:
@@ -86,14 +97,14 @@ def check_all_filenames() -> int:
     return failed_tests
 
 
-def check_source_filenames() -> int:
+def check_source_filenames(files) -> int:
     """
     Checks only source files (*.cpp, *.h, *.py, *.sh) against a stricter allowed regexp to make sure only lowercase
     alphanumerics (a-z0-9), underscores (_), hyphens (-) and dots (.) are used in source code filenames.
 
     Additionally there is an exception regexp for directories or files which are excepted from matching this regexp.
     """
-    filenames = check_output(CMD_SOURCE_FILES).decode("utf8").rstrip("\0").split("\0")
+    filenames = [filename for filename in files.keys() if re.match(ALL_SOURCE_FILENAMES_REGEXP, filename, re.IGNORECASE)]
     filename_regex = re.compile(ALLOWED_SOURCE_FILENAME_REGEXP)
     filename_exception_regex = re.compile(ALLOWED_SOURCE_FILENAME_EXCEPTION_REGEXP)
     failed_tests = 0
@@ -106,24 +117,22 @@ def check_source_filenames() -> int:
     return failed_tests
 
 
-def check_all_file_permissions() -> int:
+def check_all_file_permissions(files) -> int:
     """
     Checks all files in the repository match an allowed executable or non-executable file permission octal.
 
     Additionally checks that for executable files, the file contains a shebang line
     """
-    filenames = check_output(CMD_ALL_FILES).decode("utf8").rstrip("\0").split("\0")
     failed_tests = 0
-    for filename in filenames:
-        file_meta = FileMeta(filename)
+    for filename, file_meta in files.items():
         if file_meta.permissions == ALLOWED_PERMISSION_EXECUTABLES:
             with open(filename, "rb") as f:
                 shebang = f.readline().rstrip(b"\n")
 
             # For any file with executable permissions the first line must contain a shebang
             if not shebang.startswith(b"#!"):
                 print(
-                    f"""File "{filename}" has permission {ALLOWED_PERMISSION_EXECUTABLES} (executable) and is thus expected to contain a shebang '#!'. Add shebang or do "chmod {ALLOWED_PERMISSION_NON_EXECUTABLES} {filename}" to make it non-executable."""
+                    f"""File "{filename}" has permission {ALLOWED_PERMISSION_EXECUTABLES:03o} (executable) and is thus expected to contain a shebang '#!'. Add shebang or do "chmod {ALLOWED_PERMISSION_NON_EXECUTABLES:03o} {filename}" to make it non-executable."""
                 )
                 failed_tests += 1
 
@@ -146,14 +155,14 @@ def check_all_file_permissions() -> int:
             continue
         else:
             print(
-                f"""File "{filename}" has unexpected permission {file_meta.permissions}. Do "chmod {ALLOWED_PERMISSION_NON_EXECUTABLES} {filename}" (if non-executable) or "chmod {ALLOWED_PERMISSION_EXECUTABLES} {filename}" (if executable)."""
+                f"""File "{filename}" has unexpected permission {file_meta.permissions:03o}. Do "chmod {ALLOWED_PERMISSION_NON_EXECUTABLES:03o} {filename}" (if non-executable) or "chmod {ALLOWED_PERMISSION_EXECUTABLES:03o} {filename}" (if executable)."""
             )
             failed_tests += 1
 
     return failed_tests
 
 
-def check_shebang_file_permissions() -> int:
+def check_shebang_file_permissions(files_meta) -> int:
     """
     Checks every file that contains a shebang line to ensure it has an executable permission
     """
@@ -165,7 +174,7 @@ def check_shebang_file_permissions() -> int:
 
     failed_tests = 0
     for filename in filenames:
-        file_meta = FileMeta(filename)
+        file_meta = files_meta[filename]
         if file_meta.permissions != ALLOWED_PERMISSION_EXECUTABLES:
             # These file types are typically expected to be sourced and not executed directly
             if file_meta.full_extension in ["bash", "init", "openrc", "sh.in"]:
@@ -179,7 +188,7 @@ def check_shebang_file_permissions() -> int:
                     continue
 
             print(
-                f"""File "{filename}" contains a shebang line, but has the file permission {file_meta.permissions} instead of the expected executable permission {ALLOWED_PERMISSION_EXECUTABLES}. Do "chmod {ALLOWED_PERMISSION_EXECUTABLES} {filename}" (or remove the shebang line)."""
+                f"""File "{filename}" contains a shebang line, but has the file permission {file_meta.permissions:03o} instead of the expected executable permission {ALLOWED_PERMISSION_EXECUTABLES:03o}. Do "chmod {ALLOWED_PERMISSION_EXECUTABLES:03o} {filename}" (or remove the shebang line)."""
             )
             failed_tests += 1
     return failed_tests
@@ -188,11 +197,14 @@ def check_shebang_file_permissions() -> int:
 def main() -> NoReturn:
     root_dir = check_output(CMD_TOP_LEVEL).decode("utf8").strip()
     os.chdir(root_dir)
+
+    files = get_git_file_metadata()
+
     failed_tests = 0
-    failed_tests += check_all_filenames()
-    failed_tests += check_source_filenames()
-    failed_tests += check_all_file_permissions()
-    failed_tests += check_shebang_file_permissions()
+    failed_tests += check_all_filenames(files)
+    failed_tests += check_source_filenames(files)
+    failed_tests += check_all_file_permissions(files)
+    failed_tests += check_shebang_file_permissions(files)
 
     if failed_tests:
         print(