stringImportPaths: filename $null yields Invalid variable: null

[AMDphreak]

Summary

When stringImportPaths includes . (package root), dub expands $NAME sequences found in filenames under that tree. A file literally named $null (easy to create accidentally from PowerShell $null) makes the build fail with:

Error Invalid variable: null

No package metadata needs a $null variable — the filename alone is enough.

Repro

import subprocess, tempfile, json
from pathlib import Path

td = Path(tempfile.mkdtemp(prefix="dub-dollar-null-"))
(td / "source").mkdir()
(td / "dub.json").write_text(json.dumps({
    "name": "dollar-null-repro",
    "targetType": "executable",
    "sourceFiles": ["source/app.d"],
    "stringImportPaths": ["."]
}, indent=2), encoding="utf-8")
(td / "source" / "app.d").write_text(
    'void main() { enum s = import("note.txt"); }\n', encoding="utf-8")
(td / "note.txt").write_text("ok\n", encoding="utf-8")
# Landmine: filename looks like a dub variable
(td / "$null").write_text("artifact\n", encoding="utf-8")
print(td)
raise SystemExit(subprocess.call(["dub", "build"], cwd=td))

Expected

Build succeeds (or only expands known tokens such as $PACKAGE_DIR in build settings, not arbitrary filenames discovered under stringImportPaths).

Actual

Error Invalid variable: null

Exit code 2 during “Generating using build”, before DMD runs.

Environment

• dub 1.41.0 (built Jan 6 2026)
• DMD 2.112.0
• Windows 10/11 + PowerShell

Workarounds

• Prefer named stringImportPaths dirs (e.g. embed/, docs/) instead of .
• Delete stray $null files (can appear from PowerShell/-of$null-style mistakes)

Why it matters

stringImportPaths "." is a common pattern in dub.sdl. On Windows, PowerShell’s $null makes this footgun realistic.