[build] Rewrite 'convert.sh' into python as 'convert.py' (#1831)

The 'convert.sh' script was a bit difficult to understand. Rewrite it
using Python 3 and call it 'convert.py'

Signed-off-by: John L. Villalovos <[email protected]>

Author: JohnVillalovos

Makefile

@@ -391,9 +391,9 @@ ifeq ($(SNAPSHOT), on)
 else
 	@echo Creating C string from JS application...
 ifeq ($(BOARD), linux)
-	@./scripts/convert.sh $(JS) $(OUT)/include/zjs_script_gen.h
+	@./scripts/convert.py $(JS) $(OUT)/include/zjs_script_gen.h
 else
-	@./scripts/convert.sh $(OUT)/$(JS_TMP) $(OUT)/include/zjs_script_gen.h
+	@./scripts/convert.py $(OUT)/$(JS_TMP) $(OUT)/include/zjs_script_gen.h
 endif
 endif
 

README.md

@@ -337,7 +337,7 @@ output when you do build for Arduino 101.
 
 ## JS Minifier
 
-To save space it is recommended to use a minifier. In `convert.sh`, the script
+To save space it is recommended to use a minifier. In `convert.py`, the script
 used to encode your JS into a source file, we use `uglifyjs`. If you didn't
 install this earlier, you can do so with the command:
 ```bash

scripts/README

@@ -23,7 +23,7 @@ checkheaders
     Tries to detect whether our header files include all the header files they
     depend on.
 
-convert.sh
+convert.py
 ----------
     Runs minifier on a JavaScript file and writes it out in a C string format.
 

scripts/convert.py

@@ -0,0 +1,113 @@
+#!/usr/bin/env python3
+
+#
+# This script converts a file's ASCII data into a C char array:
+#
+# const char script_gen[] = { ........ }
+#
+
+# This script was written to be compatible with Python 3.4
+
+import argparse
+import collections
+import os
+import pathlib
+import subprocess
+import sys
+
+Uglify = collections.namedtuple("Uglify", ['content', 'used_uglifyjs'])
+
+
+def main():
+    args = parse_args()
+    minified_result = uglifyjs(args.input)
+    write_minified(args.output, minified_result)
+
+
+def write_minified(output_path, minified_result):
+    """Write the minified output, escaping things as necessary
+
+    :param output_path: A pathlib.Path() object of the output file.
+    :param minified_result: An Uglify() object containing the content to write.
+    """
+    with output_path.open('w') as out_file:
+        last_char = ""
+        print('"', end='', file=out_file)
+        for char in minified_result.content:
+            # Escape quote symbols
+            if char in ('"', ):
+                print(r'\"', end='', file=out_file)
+            elif last_char == "\\":
+                # Special case for new line and carriage return that can appear
+                # in a string e.g. print("some string\n");
+                # This is needed because BASH reads the "\n" as two characters,
+                # but in a C string it is just one character.
+                if char in ('n', 'r'):
+                    # NOTE(jlvillal): If not 'n' or 'r' we print nothing. This
+                    # is how 'convert.sh' did it.
+                    print('\\{}'.format(char), end='', file=out_file)
+            elif char == "\n":
+                if not minified_result.used_uglifyjs:
+                    print(r'\n"', end='\n"', file=out_file)
+            else:
+                print(char, end='', file=out_file)
+            last_char = char
+        print('"', end='', file=out_file)
+
+
+def uglifyjs(input_path):
+    """Run 'uglifyjs' on the input file
+
+    :param input_path: A pathlib.Path() object of the input file.
+    :returns: An Uglify() object
+    """
+    filename = str(input_path)
+    # NOTE(jlvillal): The docs say that '-nc' is the same as '--no-copyright'
+    # but in testing it is not.
+    # https://github.com/mishoo/UglifyJS/blob/2bc1d02363db3798d5df41fb5059a19edca9b7eb/README.html#L481-L483
+    ugl_args = ["-nc", "-mt"]
+
+    # uglifyjs seems to have vastly different options between versions, this
+    # should work with both
+    cmd_line = ['uglifyjs', '--version']
+    try:
+        result = subprocess.call(cmd_line, stdout=subprocess.DEVNULL)
+    except FileNotFoundError:
+        # We don't have uglifyjs, so return the contents of the file
+        return Uglify(input_path.read_text(), False)
+
+    if result == 0:
+        # We have newer uglifyjs
+        cmd_line = ['uglifyjs', filename] + ugl_args
+    else:
+        # Older uglifyjs
+        cmd_line = ['uglifyjs'] + ugl_args + [filename]
+    try:
+        output = subprocess.check_output(cmd_line)
+    except subprocess.CalledProcessError as exc:
+        print("ERROR: Minification failed!")
+        sys.exit(exc.returncode)
+    return Uglify(output.decode('utf-8'), True)
+
+
+def parse_args():
+    parser = argparse.ArgumentParser(
+        description=("Runs minifier on a JavaScript file and writes it out in "
+                     "a C string format."))
+    parser.add_argument("input", metavar='INPUT_FILE')
+    parser.add_argument("output", metavar='OUTPUT_FILE')
+    args = parser.parse_args()
+    # Make all paths absolute and expand any "~/" usage.
+    for arg_name in ('input', 'output'):
+        setattr(args, arg_name, pathlib.Path(
+            os.path.abspath(os.path.expanduser(getattr(args, arg_name)))))
+    if not args.input.is_file():
+        print("ERROR: The INPUT_FILE {!r} does not exist.".format(
+            str(args.input)))
+        parser.print_help()
+        sys.exit(1)
+    return args
+
+
+if '__main__' == __name__:
+    sys.exit(main())