bash_guard blocks cat heredoc even for a new file

CHANGELOG.md

@@ -1,5 +1,8 @@
 # Changelog
 
+## 47
+- `bash_guard` lets `cat > file <<` create a new file: Write costs the same there, so blocking only cost agents a retry (15 reports after the previous fix). Rewriting or appending to an existing project file is still refused.
+
 ## 46
 - `accept` scope check matches a scope path literally before treating `[` `*` `?` as glob: router directories like `[slug]` are names, and the check reported files under them as outside scope (4 reports).
 

hooks/bash_guard.py

@@ -1,8 +1,9 @@
 #!/usr/bin/env python3
 """PreToolUse hook (Bash): refuse editing project files through the shell (sed -i, perl -i, cat > file <<, python3 -
 heredocs that write); Edit/Write pay only the change. Exit 2 = blocked. Temporary and git-ignored files (build
-output) pass; echo/tee > file are not covered on purpose."""
+output) and new files from cat heredocs pass; echo/tee > file are not covered on purpose."""
 import json
+import os
 import re
 import subprocess
 import sys
@@ -48,6 +49,8 @@ def edits(ln):
             continue
         seg = re.split(r"[|;&]", ln[m.end():], maxsplit=1)[0]  # this command only, not `; rm /tmp/x` after it
         target = m.group(1) if m.groups() else (seg.split() or [""])[-1]
+        if what == "cat > file <<" and not os.path.exists(target):  # a new file: Write would cost the same
+            continue
         if not scratch(target):
             return what
     return None
@@ -67,7 +70,7 @@ def main():
     if not hits:
         return 0
     print(f"dpcli: {hits[0]} edits project files through the shell. Read the file first (cat in Bash does not count), "
-          f"then Edit (exact replacement); a new file — Write; bulk renames: ast-grep run -p OLD -r NEW -U. "
+          f"then Edit (exact replacement); a new file — Write or cat > file <<; bulk renames: ast-grep run -p OLD -r NEW -U. "
           f"Temporary (/tmp) and git-ignored files (build/) are fine.", file=sys.stderr)
     return 2
 

lib/dpcli/__init__.py

@@ -6,4 +6,4 @@
 else in the current copy. Exit codes: 0 ok, 1 error/check failed, 2 arguments.
 """
 
-VERSION = 46 # bump on every change: older copies re-exec from the main copy (reexec.maybe_reexec)
+VERSION = 47# bump on every change: older copies re-exec from the main copy (reexec.maybe_reexec)

tests/test_bash_guard.py

@@ -25,7 +25,7 @@ def test_blocks_shell_edits(self):
                     "sed -n -i 's/a/b/' f", "sed -e 's/a/b/' -i f", "perl -e 's/a/b/' -pi f",  # -i anywhere
                     "echo \"<<EOF\"\nsed -i 's/a/b/' f",  # a quoted "<<EOF" opens no heredoc
                     "sed -i s/a/b/ src/x.ts; rm /tmp/y", "sed -i s/a/b/ src/x.ts && rm /tmp/z",  # target of its own segment
-                    "cat > src/x.ts <<'EOF'\nx\nEOF", "python3 - <<'EOF'\nfrom pathlib import Path\nPath('a').write_text('x')\nEOF",
+                    "python3 - <<'EOF'\nfrom pathlib import Path\nPath('a').write_text('x')\nEOF",
                     "python3 - <<'EOF'\nopen('a', 'w').write('x')\nEOF"):
             code, err = run(cmd)
             self.assertEqual(code, 2, cmd)
@@ -41,6 +41,17 @@ def test_allows_git_ignored_targets(self):
             self.assertEqual(run(cmd, p.root)[0], 0, cmd)
         self.assertEqual(run("sed -i s/a/b/ src/x.ts", p.root)[0], 2)
 
+    def test_cat_heredoc_blocks_existing_files_only(self):  # a new file costs Write the same: nothing to save
+        p = Project()
+        self.addCleanup(p.cleanup)
+        (p.root / "src").mkdir(exist_ok=True)
+        (p.root / "src/x.ts").write_text("x")
+        for cmd in ("cat > src/x.ts <<'EOF'\ny\nEOF", "cat >> src/x.ts <<'EOF'\ny\nEOF"):
+            code, err = run(cmd, p.root)
+            self.assertEqual(code, 2, cmd)
+            self.assertIn("Edit", err)
+        self.assertEqual(run("cat > src/new.ts <<'EOF'\ny\nEOF", p.root)[0], 0)
+
     def test_allows_programs_reads_and_quoted_text(self):
         for cmd in ("rg -n foo src", "sed -n '1,20p' f", "python3 - <<'EOF'\nprint(1)\nEOF", "cat f | jq .",
                     "pnpm exec vitest run", ".dpcli/dpcli review X --from - <<'JSON'\n{}\nJSON",