feat: Formatting changes

1 files changed, 128 insertions, 0 deletions

diff --git a/tabify-nix.py b/tabify-nix.py
new file mode 100755
index 0000000..0220ab9
--- /dev/null
+++ b/tabify-nix.py
@@ -0,0 +1,128 @@
+#!/usr/bin/env python3
+"""Convert nixfmt's 2-space indentation to tabs.
+
+Usage: ./tabify-nix.py [FILE...]   (default: every git-tracked .nix file)
+
+Only lines that start in code are touched. Lines that start inside a string
+('' or ") are left exactly as they are, because Nix only strips leading
+*spaces* from '' strings, so tabs there would change the string's value.
+"""
+import subprocess
+import sys
+
+INDENT = 2
+
+
+def lex_line(line, stack):
+    """Advance the lexer state `stack` over one line (mutates it in place).
+
+    Stack entries: ["code", brace_depth], ["ind"] (''), ["dq"] ("), ["block"].
+    A "code" entry above a string entry is a ${ } interpolation.
+    """
+    i, n = 0, len(line)
+    while i < n:
+        mode = stack[-1][0]
+        rest = line[i:]
+        if mode == "code":
+            c = line[i]
+            if c == "#":
+                return
+            if rest.startswith("/*"):
+                stack.append(["block"])
+                i += 2
+            elif c == '"':
+                stack.append(["dq"])
+                i += 1
+            elif rest.startswith("''"):
+                stack.append(["ind"])
+                i += 2
+            elif c == "{":
+                stack[-1][1] += 1
+                i += 1
+            elif c == "}":
+                if stack[-1][1] == 0 and len(stack) > 1:
+                    stack.pop()  # end of ${ } interpolation
+                else:
+                    stack[-1][1] -= 1
+                i += 1
+            else:
+                i += 1
+        elif mode == "block":
+            if rest.startswith("*/"):
+                stack.pop()
+                i += 2
+            else:
+                i += 1
+        elif mode == "dq":
+            if rest.startswith("\\"):
+                i += 2
+            elif rest.startswith("$${"):
+                i += 3
+            elif rest.startswith("${"):
+                stack.append(["code", 0])
+                i += 2
+            elif rest.startswith('"'):
+                stack.pop()
+                i += 1
+            else:
+                i += 1
+        elif mode == "ind":
+            if rest.startswith("'''") or rest.startswith("''$"):
+                i += 3
+            elif rest.startswith("''\\"):
+                i += 4
+            elif rest.startswith("''"):
+                stack.pop()
+                i += 2
+            elif rest.startswith("$${"):
+                i += 3
+            elif rest.startswith("${"):
+                stack.append(["code", 0])
+                i += 2
+            else:
+                i += 1
+
+
+def tabify(text):
+    stack = [["code", 0]]
+    out = []
+    for line in text.split("\n"):
+        if stack[-1][0] in ("code", "block"):
+            stripped = line.lstrip(" \t")
+            ws = line[: len(line) - len(stripped)]
+            if stripped:
+                tabs = ws.count("\t")
+                spaces = ws.count(" ")
+                line = "\t" * (tabs + spaces // INDENT) + " " * (spaces % INDENT) + stripped
+            else:
+                line = ""
+        out.append(line)
+        lex_line(line, stack)
+    if stack != [["code", 0]]:
+        raise ValueError(f"unbalanced lexer state at EOF: {stack}")
+    return "\n".join(out)
+
+
+def main():
+    files = sys.argv[1:] or subprocess.run(
+        ["git", "ls-files", "*.nix"], capture_output=True, text=True, check=True
+    ).stdout.split()
+    failed = False
+    for path in files:
+        with open(path) as f:
+            src = f.read()
+        try:
+            new = tabify(src)
+        except ValueError as e:
+            print(f"{path}: {e}, skipped", file=sys.stderr)
+            failed = True
+            continue
+        if new != src:
+            with open(path, "w") as f:
+                f.write(new)
+            print(f"tabified {path}")
+    sys.exit(1 if failed else 0)
+
+
+if __name__ == "__main__":
+    main()