fix: install zsh completion into an existing fpath directory

docs/completion.rst

@@ -14,10 +14,11 @@ your shell:
 
    nnote --install-completion
 
-This does **not** modify any shell config file. The script is placed in:
+This does **not** modify any shell config file. The script is placed in an
+appropriate completion directory for your shell:
 
 - **bash** — ``~/.local/share/bash-completion/completions/nnote``
-- **zsh** — ``~/.local/share/zsh/site-functions/_nnote``
+- **zsh** — the first user-writable directory already in your ``$fpath``
 - **fish** — ``~/.config/fish/completions/nnote.fish``
 
 To inspect the script before installing, use:

nnote/completions.py

@@ -46,17 +46,43 @@ def show_completion_callback(ctx, param, value):
     ctx.exit()
 
 
+def _zsh_install_path():
+    import subprocess
+
+    result = subprocess.run(
+        ["zsh", "-i", "-c", "print -l $fpath"],
+        capture_output=True,
+        text=True,
+    )
+    home = Path.home()
+    for line in result.stdout.splitlines():
+        p = Path(line.strip())
+        if not p.is_absolute():
+            continue
+        try:
+            p.relative_to(home)
+        except ValueError:
+            continue
+        if p.exists() and p.is_dir():
+            return p / "_nnote"
+    return _COMPLETION_FILE["zsh"].expanduser()
+
+
 def install_completion_callback(ctx, param, value):
     if not value or ctx.resilient_parsing:
         return
     shell = _detect_shell()
-    script_file = _COMPLETION_FILE[shell].expanduser()
+    if shell == "zsh":
+        script_file = _zsh_install_path()
+    else:
+        script_file = _COMPLETION_FILE[shell].expanduser()
     if script_file.exists():
         click.echo(f"Completion already installed in {script_file}")
         ctx.exit()
     script_file.parent.mkdir(parents=True, exist_ok=True)
     script_file.write_text(_generate_script(shell, ctx.command))
     click.echo(f"Completion installed in {script_file}")
+    click.echo("Restart your shell for the change to take effect.")
     ctx.exit()
 
 

tests/test_completions.py

@@ -1,12 +1,16 @@
 from pathlib import Path
-from unittest.mock import patch
+from unittest.mock import patch, MagicMock
 
 import pytest
 from click.shell_completion import CompletionItem
 from click.testing import CliRunner
 
 from nnote.cli import cli
-from nnote.completions import complete_note_titles, complete_directories
+from nnote.completions import (
+    complete_note_titles,
+    complete_directories,
+    _zsh_install_path,
+)
 from nnote.config import Config
 
 
@@ -127,7 +131,7 @@ def test_show_completion():
 def test_install_completion(tmp_path):
     script_file = tmp_path / "_nnote"
     with patch("nnote.completions._detect_shell", return_value="zsh"):
-        with patch("nnote.completions._COMPLETION_FILE", {"zsh": script_file}):
+        with patch("nnote.completions._zsh_install_path", return_value=script_file):
             result = CliRunner().invoke(cli, ["--install-completion"])
     assert result.exit_code == 0
     assert script_file.exists()
@@ -138,8 +142,48 @@ def test_install_completion_idempotent(tmp_path):
     script_file = tmp_path / "_nnote"
     script_file.write_text("# existing script\n")
     with patch("nnote.completions._detect_shell", return_value="zsh"):
-        with patch("nnote.completions._COMPLETION_FILE", {"zsh": script_file}):
+        with patch("nnote.completions._zsh_install_path", return_value=script_file):
             result = CliRunner().invoke(cli, ["--install-completion"])
     assert result.exit_code == 0
     assert "already installed" in result.output
     assert script_file.read_text() == "# existing script\n"
+
+
+def test_install_completion_bash(tmp_path):
+    script_file = tmp_path / "nnote"
+    with patch("nnote.completions._detect_shell", return_value="bash"):
+        with patch("nnote.completions._COMPLETION_FILE", {"bash": script_file}):
+            result = CliRunner().invoke(cli, ["--install-completion"])
+    assert result.exit_code == 0
+    assert script_file.exists()
+    assert "_NNOTE_COMPLETE" in script_file.read_text()
+
+
+# --- _zsh_install_path ---
+
+
+def test_zsh_install_path_picks_first_writable_home_fpath_dir(tmp_path):
+    user_dir = tmp_path / "zsh" / "functions"
+    user_dir.mkdir(parents=True)
+    system_dir = Path("/usr/share/zsh/functions")
+
+    mock_result = MagicMock()
+    mock_result.stdout = f"{system_dir}\n{user_dir}\n"
+
+    with patch("subprocess.run", return_value=mock_result):
+        with patch("nnote.completions.Path.home", return_value=tmp_path):
+            path = _zsh_install_path()
+
+    assert path == user_dir / "_nnote"
+
+
+def test_zsh_install_path_falls_back_to_xdg_when_no_home_fpath(tmp_path):
+    mock_result = MagicMock()
+    mock_result.stdout = (
+        "/usr/share/zsh/functions\n/usr/local/share/zsh/site-functions\n"
+    )
+
+    with patch("subprocess.run", return_value=mock_result):
+        path = _zsh_install_path()
+
+    assert path == Path("~/.local/share/zsh/site-functions/_nnote").expanduser()