Clean up and modernize Python support code

Switches to safer and more modern idioms, and addresses many issues raised by
flake8 and pylint.

1 files changed, 66 insertions, 59 deletions

diff --git a/plugins/literasc.py b/plugins/literasc.py
index 82ee226..74b13a7 100755
--- a/plugins/literasc.py
+++ b/plugins/literasc.py
@@ -1,13 +1,16 @@
 #!/usr/bin/env python3
-# -*- coding: utf-8 -*-
-#
-# Literasc, a simple literate programming tool for C, C++, and Turtle.
-# Copyright 2012 David Robillard <d@drobilla.net>
-#
-# Unlike many LP tools, this tool uses normal source code as input, there is no
-# tangle/weave and no special file format.  The literate parts of the program
-# are written in comments, which are emitted as paragraphs of regular text
-# interleaved with code.  Asciidoc is both the comment and output syntax.
+
+# Copyright 2012-2022 David Robillard <d@drobilla.net>
+# SPDX-License-Identifier: ISC
+
+"""
+A simple literate programming tool for C, C++, and Turtle.
+
+Unlike many LP tools, this tool uses normal source code as input, there is no
+tangle/weave and no special file format.  The literate parts of the program are
+written in comments, which are emitted as paragraphs of regular text
+interleaved with code.  Asciidoc is both the comment and output syntax.
+"""
 
 import os
 import re
@@ -15,74 +18,81 @@ import sys
 
 
 def format_text(text):
-    "Format a text (comment) fragment and return it as a marked up string"
+    "Format a text (comment) fragment and return it as a marked up string."
     return "\n\n" + re.sub("\n *", "\n", text.strip()) + "\n\n"
 
 
 def format_code(lang, code):
+    "Format a block of code and return it as a marked up string."
+
     if code.strip() == "":
         return code
 
-    head = "[source,%s]" % lang
-    sep = "-" * len(head) + "\n"
-    return head + "\n" + sep + code.strip("\n") + "\n" + sep
+    head = f"[source,{lang}]"
+    code = code.strip("\n")
+    sep = "-" * len(head)
+    return "\n".join([head, sep, code, sep]) + "\n"
 
 
-def format_c_source(filename, file):
-    output = "=== %s ===\n" % os.path.basename(filename)
+def format_c_source(filename, in_file):
+    "Format an annotated C source file as a marked up string."
+
+    output = f"=== {os.path.basename(filename)} ===\n"
     chunk = ""
     prev_c = 0
     in_comment = False
     in_comment_start = False
     n_stars = 0
-    code = ""
-    for line in file:
-        code += line
+    code = "".join(in_file)
 
     # Skip initial license comment
     if code[0:2] == "/*":
-        code = code[code.find("*/") + 2 :]
+        end = code.find("*/") + 2
+        code = code[end:]
+
+    def last_chunk(chunk):
+        length = len(chunk) - 1
+        return chunk[0:length]
 
-    for c in code:
-        if prev_c == "/" and c == "*":
+    for char in code:
+        if prev_c == "/" and char == "*":
             in_comment_start = True
             n_stars = 1
         elif in_comment_start:
-            if c == "*":
+            if char == "*":
                 n_stars += 1
             else:
                 if n_stars > 1:
-                    output += format_code("c", chunk[0 : len(chunk) - 1])
+                    output += format_code("c", last_chunk(chunk))
                     chunk = ""
                     in_comment = True
                 else:
-                    chunk += "*" + c
+                    chunk += "*" + char
                 in_comment_start = False
-        elif in_comment and prev_c == "*" and c == "/":
+        elif in_comment and prev_c == "*" and char == "/":
             if n_stars > 1:
-                output += format_text(chunk[0 : len(chunk) - 1])
+                output += format_text(last_chunk(chunk))
             else:
-                output += format_code(
-                    "c", "/* " + chunk[0 : len(chunk) - 1] + "*/"
-                )
+                output += format_code("c", "/* " + last_chunk(chunk) + "*/")
             in_comment = False
             in_comment_start = False
             chunk = ""
-        elif in_comment_start and c == "*":
-            n_stars += 1
         else:
-            chunk += c
-        prev_c = c
+            chunk += char
+
+        prev_c = char
 
     return output + format_code("c", chunk)
 
 
-def format_ttl_source(filename, file):
-    output = "=== %s ===\n" % os.path.basename(filename)
+def format_ttl_source(filename, in_file):
+    "Format an annotated Turtle source file as a marked up string."
+
+    output = f"=== {os.path.basename(filename)} ===\n"
 
     in_comment = False
     chunk = ""
-    for line in file:
+    for line in in_file:
         is_comment = line.strip().startswith("#")
         if in_comment:
             if is_comment:
@@ -101,36 +111,33 @@ def format_ttl_source(filename, file):
 
     if in_comment:
         return output + format_text(chunk)
-    else:
-        return output + format_code("turtle", chunk)
+
+    return output + format_code("turtle", chunk)
 
 
 def gen(out, filenames):
-    for filename in filenames:
-        file = open(filename)
-        if not file:
-            sys.stderr.write("Failed to open file %s\n" % filename)
-            continue
-
-        if filename.endswith(".c") or filename.endswith(".h"):
-            out.write(format_c_source(filename, file))
-        elif filename.endswith(".ttl") or filename.endswith(".ttl.in"):
-            out.write(format_ttl_source(filename, file))
-        elif filename.endswith(".txt"):
-            for line in file:
-                out.write(line)
-            out.write("\n")
-        else:
-            sys.stderr.write(
-                "Unknown source format `%s'" % (filename[filename.find(".") :])
-            )
+    "Write markup generated from filenames to an output file."
 
-        file.close()
+    for filename in filenames:
+        with open(filename, "r", encoding="utf-8") as in_file:
+            if filename.endswith(".c") or filename.endswith(".h"):
+                out.write(format_c_source(filename, in_file))
+            elif filename.endswith(".ttl") or filename.endswith(".ttl.in"):
+                out.write(format_ttl_source(filename, in_file))
+            elif filename.endswith(".txt"):
+                for line in in_file:
+                    out.write(line)
+                out.write("\n")
+            else:
+                sys.stderr.write(
+                    f"Unknown source format `{filename.splitext()[1]}`\n"
+                )
 
 
 if __name__ == "__main__":
     if len(sys.argv) < 2:
-        sys.stderr.write("Usage: %s FILENAME...\n" % sys.argv[1])
+        sys.stderr.write(f"Usage: {sys.argv[0]} OUT_FILE IN_FILE...\n")
         sys.exit(1)
 
-    gen(sys.argv[1:])
+    with open(sys.argv[1], "w", encoding="utf-8") as out_file:
+        gen(out_file, sys.argv[2:])