create-sys-script: adapt to separate build dir, modernize, add more checks

The script wasn't apparently used since the switch to meson, because
it required the sys subdirectory to be present in the same subdirectory
where the output script is located.

Let's use f-strings to make the whole thing more readable. Add some
extra checks.

test/create-sys-script.py

@@ -26,10 +26,12 @@ OUTFILE_HEADER = """#!/usr/bin/env python3
 # after adding or modifying anything in the test/sys/ directory
 
 
-import os, sys, stat, tempfile, filecmp
+import os, sys
+import stat
+import tempfile
+import filecmp
+import subprocess
 
-
-OUTFILE = "sys-script.py"
 OUTFILE_MODE = 0o775
 
 OUTFILE_FUNCS = r"""
@@ -45,7 +47,6 @@ def f(path, mode, contents):
     with open(path, "wb") as f:
         f.write(contents)
     os.chmod(path, mode)
-
 """
 
 OUTFILE_MAIN = """
@@ -62,12 +63,12 @@ os.chdir(sys.argv[1])
 
 def handle_dir(outfile, path):
     m = os.lstat(path).st_mode & 0o777
-    outfile.write("d('{}', {:#o})\n".format(path, m))
+    outfile.write(f"d('{path}', {m:#o})\n")
 
 
 def handle_link(outfile, path):
     src = os.readlink(path)
-    outfile.write("l('{}', '{}')\n".format(path, src))
+    outfile.write(f"l('{path}', '{src}')\n")
 
 
 def escape_single_quotes(b):
@@ -85,15 +86,15 @@ def handle_file(outfile, path):
     with open(path, "rb") as f:
         b = f.read()
     if b.count(b"\n") > 1:
-        r = "\n".join([ escape_single_quotes(l) for l in b.split(b"\n") ])
-        r = "b'''{r}'''".format(r=r)
+        r = "\n".join( escape_single_quotes(l) for l in b.split(b"\n") )
+        r = f"b'''{r}'''"
     else:
         r = repr(b)
-    outfile.write("f('{}', {:#o}, {})\n".format(path, m, r))
+    outfile.write(f"f('{path}', {m:#o}, {r})\n")
 
 
 def process_sysdir(outfile):
-    for (dirpath, dirnames, filenames) in os.walk("sys"):
+    for (dirpath, dirnames, filenames) in os.walk('sys'):
         handle_dir(outfile, dirpath)
         for d in dirnames:
             path = os.path.join(dirpath, d)
@@ -139,7 +140,9 @@ def verify_file(tmpd, path_a):
 
 
 def verify_script(tmpd):
+    any = False
     for (dirpath, dirnames, filenames) in os.walk("sys"):
+        any = True
         try:
             path = dirpath
             verify_dir(tmpd, path)
@@ -155,29 +158,31 @@ def verify_script(tmpd):
                     elif stat.S_ISREG(mode):
                         verify_file(tmpd, path)
         except Exception:
-            print("FAIL on '{}'".format(path), file=sys.stderr)
+            print(f'FAIL on "{path}"', file=sys.stderr)
             raise
-
+    if not any:
+        exit('Nothing found!')
 
 if __name__ == "__main__":
-    # Always operate in the dir where this script is
-    os.chdir(os.path.dirname(sys.argv[0]))
+    if len(sys.argv) < 2:
+        exit('Usage: create-sys-script.py /path/to/test/')
 
-    if not os.path.isdir("sys"):
-        exit("No sys/ directory; please create before running this")
+    outfile = os.path.abspath(os.path.dirname(sys.argv[0]) + '/sys-script.py')
+    print(f'Creating {outfile} using contents of {sys.argv[1]}/sys')
 
-    print("Creating {} using contents of sys/".format(OUTFILE))
+    os.chdir(sys.argv[1])
 
-    with open(OUTFILE, "w") as f:
-        os.chmod(OUTFILE, OUTFILE_MODE)
-        f.write(OUTFILE_HEADER.replace(os.path.basename(sys.argv[0]), OUTFILE))
+    with open(outfile, "w") as f:
+        os.chmod(outfile, OUTFILE_MODE)
+        f.write(OUTFILE_HEADER.replace(os.path.basename(sys.argv[0]),
+                                       os.path.basename(outfile)))
         f.write(OUTFILE_FUNCS)
         f.write(OUTFILE_MAIN)
         process_sysdir(f)
 
     with tempfile.TemporaryDirectory() as tmpd:
-        print("Recreating sys/ using {} at {}".format(OUTFILE, tmpd))
-        os.system("./{script} {tmpd}".format(script=OUTFILE, tmpd=tmpd))
+        print(f'Recreating sys/ using {outfile} at {tmpd}')
+        subprocess.check_call([outfile, tmpd])
         verify_script(tmpd)
 
-    print("Verification successful, {} is correct".format(OUTFILE))
+    print(f'Verification successful, {outfile} is correct')

test/sys-script.py

@@ -32,7 +32,6 @@ def f(path, mode, contents):
         f.write(contents)
     os.chmod(path, mode)
 
-
 if len(sys.argv) < 2:
     exit("Usage: {} <target dir>".format(sys.argv[0]))