[devscripts] `tomlparse`: Add makeshift toml parser

Authored by: Grub4K

diff --git a/devscripts/tomlparse.py b/devscripts/tomlparse.py
new file mode 100755 (executable)
index 0000000..85ac4ee
--- /dev/null
+++ b/devscripts/tomlparse.py
@@ -0,0 +1,189 @@
+#!/usr/bin/env python3
+
+"""
+Simple parser for spec compliant toml files
+
+A simple toml parser for files that comply with the spec.
+Should only be used to parse `pyproject.toml` for `install_deps.py`.
+
+IMPORTANT: INVALID FILES OR MULTILINE STRINGS ARE NOT SUPPORTED!
+"""
+
+from __future__ import annotations
+
+import datetime
+import json
+import re
+
+WS = r'(?:[\ \t]*)'
+STRING_RE = re.compile(r'"(?:\\.|[^\\"\n])*"|\'[^\'\n]*\'')
+SINGLE_KEY_RE = re.compile(rf'{STRING_RE.pattern}|[A-Za-z0-9_-]+')
+KEY_RE = re.compile(rf'{WS}(?:{SINGLE_KEY_RE.pattern}){WS}(?:\.{WS}(?:{SINGLE_KEY_RE.pattern}){WS})*')
+EQUALS_RE = re.compile(rf'={WS}')
+WS_RE = re.compile(WS)
+
+_SUBTABLE = rf'(?P<subtable>^\[(?P<is_list>\[)?(?P<path>{KEY_RE.pattern})\]\]?)'
+EXPRESSION_RE = re.compile(rf'^(?:{_SUBTABLE}|{KEY_RE.pattern}=)', re.MULTILINE)
+
+LIST_WS_RE = re.compile(rf'{WS}((#[^\n]*)?\n{WS})*')
+LEFTOVER_VALUE_RE = re.compile(r'[^,}\]\t\n#]+')
+
+
+def parse_key(value: str):
+    for match in SINGLE_KEY_RE.finditer(value):
+        if match[0][0] == '"':
+            yield json.loads(match[0])
+        elif match[0][0] == '\'':
+            yield match[0][1:-1]
+        else:
+            yield match[0]
+
+
+def get_target(root: dict, paths: list[str], is_list=False):
+    target = root
+
+    for index, key in enumerate(paths, 1):
+        use_list = is_list and index == len(paths)
+        result = target.get(key)
+        if result is None:
+            result = [] if use_list else {}
+            target[key] = result
+
+        if isinstance(result, dict):
+            target = result
+        elif use_list:
+            target = {}
+            result.append(target)
+        else:
+            target = result[-1]
+
+    assert isinstance(target, dict)
+    return target
+
+
+def parse_enclosed(data: str, index: int, end: str, ws_re: re.Pattern):
+    index += 1
+
+    if match := ws_re.match(data, index):
+        index = match.end()
+
+    while data[index] != end:
+        index = yield True, index
+
+        if match := ws_re.match(data, index):
+            index = match.end()
+
+        if data[index] == ',':
+            index += 1
+
+        if match := ws_re.match(data, index):
+            index = match.end()
+
+    assert data[index] == end
+    yield False, index + 1
+
+
+def parse_value(data: str, index: int):
+    if data[index] == '[':
+        result = []
+
+        indices = parse_enclosed(data, index, ']', LIST_WS_RE)
+        valid, index = next(indices)
+        while valid:
+            index, value = parse_value(data, index)
+            result.append(value)
+            valid, index = indices.send(index)
+
+        return index, result
+
+    if data[index] == '{':
+        result = {}
+
+        indices = parse_enclosed(data, index, '}', WS_RE)
+        valid, index = next(indices)
+        while valid:
+            valid, index = indices.send(parse_kv_pair(data, index, result))
+
+        return index, result
+
+    if match := STRING_RE.match(data, index):
+        return match.end(), json.loads(match[0]) if match[0][0] == '"' else match[0][1:-1]
+
+    match = LEFTOVER_VALUE_RE.match(data, index)
+    assert match
+    value = match[0].strip()
+    for func in [
+        int,
+        float,
+        datetime.time.fromisoformat,
+        datetime.date.fromisoformat,
+        datetime.datetime.fromisoformat,
+        {'true': True, 'false': False}.get,
+    ]:
+        try:
+            value = func(value)
+            break
+        except Exception:
+            pass
+
+    return match.end(), value
+
+
+def parse_kv_pair(data: str, index: int, target: dict):
+    match = KEY_RE.match(data, index)
+    if not match:
+        return None
+
+    *keys, key = parse_key(match[0])
+
+    match = EQUALS_RE.match(data, match.end())
+    assert match
+    index = match.end()
+
+    index, value = parse_value(data, index)
+    get_target(target, keys)[key] = value
+    return index
+
+
+def parse_toml(data: str):
+    root = {}
+    target = root
+
+    index = 0
+    while True:
+        match = EXPRESSION_RE.search(data, index)
+        if not match:
+            break
+
+        if match.group('subtable'):
+            index = match.end()
+            path, is_list = match.group('path', 'is_list')
+            target = get_target(root, list(parse_key(path)), bool(is_list))
+            continue
+
+        index = parse_kv_pair(data, match.start(), target)
+        assert index is not None
+
+    return root
+
+
+def main():
+    import argparse
+    from pathlib import Path
+
+    parser = argparse.ArgumentParser()
+    parser.add_argument('infile', type=Path, help='The TOML file to read as input')
+    args = parser.parse_args()
+
+    with args.infile.open('r', encoding='utf-8') as file:
+        data = file.read()
+
+    def default(obj):
+        if isinstance(obj, (datetime.date, datetime.time, datetime.datetime)):
+            return obj.isoformat()
+
+    print(json.dumps(parse_toml(data), default=default))
+
+
+if __name__ == '__main__':
+    main()