Implement a python Dockerfile parser.

This tool can translate Dockerfiles into shell scripts and JSON
structures. It is imagined to be used for the blend concept, where a
Dockerfile could be a system and can be translated into a blend file,
and used by an sdk.

extra/dockerfile_parse.py

@@ -0,0 +1,149 @@
+#!/usr/bin/env python
+# Copyright (c) 2018 Dyne.org Foundation
+# libdevuansdk is maintained by Ivan J. <parazyd@dyne.org>
+#
+# This file is part of libdevuansdk
+#
+# This source code is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This software is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this source code. If not, see <http://www.gnu.org/licenses/>.
+"""
+Dockerfile parser module
+"""
+from argparse import ArgumentParser
+from sys import stdin
+import json
+import re
+
+
+def rstrip_backslash(line):
+    """
+    Strip backslashes from end of line
+    """
+    line = line.rstrip()
+    if line.endswith('\\'):
+        return line[:-1]
+    return line
+
+
+def parse_instruction(inst):
+    """
+    Method for translating Dockerfile instructions to shell script
+    """
+    ins = inst['instruction'].upper()
+    val = inst['value']
+
+    # Valid Dockerfile instructions
+    cmds = ['ADD', 'ARG', 'CMD', 'COPY', 'ENTRYPOINT', 'ENV', 'EXPOSE', 'FROM',
+            'HEALTHCHECK', 'LABEL', 'MAINTAINER', 'ONBUILD', 'RUN', 'SHELL',
+            'STOPSIGNAL', 'USER', 'VOLUME', 'WORKDIR']
+
+    if ins == 'ADD':
+        cmds.remove(ins)
+        val = val.replace('$', '\\$')
+        args = val.split(' ')
+        return 'wget -O %s %s\n' % (args[1], args[0])
+
+    elif ins == 'ARG':
+        cmds.remove(ins)
+        return '%s\n' % val
+
+    elif ins == 'ENV':
+        cmds.remove(ins)
+        if '=' not in val:
+            val = val.replace(' ', '=', 1)
+        return 'export %s\n' % val
+
+    elif ins == 'RUN':
+        cmds.remove(ins)
+        # Replace `` with $()
+        while '`' in val:
+            val = val.replace('`', '"$(', 1)
+            val = val.replace('`', ')"', 1)
+        return '%s\n' % val.replace('$', '\\$')
+
+    elif ins == 'WORKDIR':
+        cmds.remove(ins)
+        return 'mkdir -p %s && cd %s\n' % (val, val)
+
+    elif ins in cmds:
+        # TODO: Look at CMD being added to /etc/rc.local
+        return '#\n# %s not implemented\n# Instruction: %s %s\n#\n' % \
+            (ins, ins, val)
+
+
+def main():
+    """
+    Main parsing routine
+    """
+    parser = ArgumentParser()
+    parser.add_argument('-j', '--json', action='store_true',
+                        help='output the data as a JSON structure')
+    parser.add_argument('-s', '--shell', action='store_true',
+                        help='output the data as a shell script (default)')
+    parser.add_argument('--keeptabs', action='store_true',
+                        help='do not replace \\t (tabs) in the strings')
+    parser.add_argument('Dockerfile')
+    args = parser.parse_args()
+
+    if args.Dockerfile != '-':
+        with open(args.Dockerfile) as file:
+            data = file.read().splitlines()
+    else:
+        data = stdin.read().splitlines()
+
+    instre = re.compile(r'^\s*(\w+)\s+(.*)$')
+    contre = re.compile(r'^.*\\\s*$')
+    commentre = re.compile(r'^\s*#')
+
+    instructions = []
+    lineno = -1
+    in_continuation = False
+    cur_inst = {}
+
+    for line in data:
+        lineno += 1
+        if commentre.match(line):
+            continue
+        if not in_continuation:
+            rematch = instre.match(line)
+            if not rematch:
+                continue
+            cur_inst = {
+                'instruction': rematch.groups()[0].upper(),
+                'value': rstrip_backslash(rematch.groups()[1]),
+            }
+        else:
+            if cur_inst['value']:
+                cur_inst['value'] += rstrip_backslash(line)
+            else:
+                cur_inst['value'] = rstrip_backslash(line.lstrip())
+
+        in_continuation = contre.match(line)
+        if not in_continuation and cur_inst is not None:
+            if not args.keeptabs:
+                cur_inst['value'] = cur_inst['value'].replace('\t', '')
+            instructions.append(cur_inst)
+
+    if args.json:
+        print(json.dumps(instructions))
+        return
+
+    # Default to shell script output
+    script = '#!/bin/sh\n'
+    for i in instructions:
+        script += parse_instruction(i)
+    print(script)
+
+
+if __name__ == '__main__':
+    main()