[IMP] todo: offer to install textual instead of just naming it

« Installez textual pour le TUI (pip) » left the user to work out which pip,
which interpreter, which package — and it was printed from eight different
places. Every TUI screen now asks:

  ⚠  Textual est nécessaire pour cet écran.
  L'installer maintenant ? (O/n, défaut : oui)

The command targets sys.executable, the interpreter that will have to import
it — installing a distribution package would land somewhere the venv never
looks. Outside a venv it adds --user, which is also what gets past the refusal
of distributions whose environment is externally managed (PEP 668).

Two details that decide whether this works at all:

  · importlib.invalidate_caches() after installing. A failed import is
    remembered, so without it textual stays « missing » for the rest of the
    session despite having just been installed.
  · a pip that exits non-zero never reports success. The check is « is it
    importable NOW », not « did pip return 0 », and the failure suggests the
    distribution package by name.

It lives in its own module rather than as a TODO method: todo_upgrade needs it
too and is imported BY todo, so putting it there would close a cycle.

One call site is deliberately NOT converted. The statistics screen only reads
files; it never touches Textual, and its old message claimed otherwise. An
import failure there is a real module problem and now says so.

Verified: already-present asks nothing and runs nothing; refusal installs
nothing; pip failing returns False and points at python3-textual; pip
succeeding returns True; prompt=False reports without asking. Then each of the
four TUI entries — telemetry, deploy form, deploy progress, migration resume —
offers and falls back cleanly on refusal, while the statistics screen stays
silent.

Also caught by those tests: « import importlib » alone does not expose
importlib.util, so availability could not be checked at all.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

script/todo/textual_setup.py

@@ -0,0 +1,89 @@
+#!/usr/bin/env python3
+# © 2021-2026 TechnoLibre (http://www.technolibre.ca)
+# License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl)
+"""Disponibilité de Textual, et installation à la demande.
+
+Les écrans TUI du CLI TODO (télémétrie, dashboard d'installation, formulaire
+de déploiement, reprise de migration) dépendent tous de Textual. Sans lui, ils
+se contentaient d'un « Installez textual (pip) » qui laissait l'utilisateur
+chercher la bonne commande pour son système.
+
+`ensure(...)` répond à la question à sa place : Textual est-il là, et sinon
+veut-on l'installer maintenant ?
+
+Module à part, et non une méthode de `TODO` : `todo_upgrade` en a besoin
+aussi, et il est importé PAR `todo` — le mettre là créerait un cycle.
+"""
+from __future__ import annotations
+
+import importlib
+import importlib.util  # « import importlib » seul n'expose PAS .util
+import subprocess
+import sys
+
+try:
+    from script.todo.todo_i18n import t
+except Exception:  # pragma: no cover - repli si i18n indisponible
+
+    def t(key: str) -> str:
+        return key
+
+
+def available() -> bool:
+    """Textual est-il importable maintenant ?"""
+    return importlib.util.find_spec("textual") is not None
+
+
+def in_venv() -> bool:
+    """Vrai si l'interpréteur courant est dans un environnement virtuel."""
+    return sys.prefix != getattr(sys, "base_prefix", sys.prefix)
+
+
+def install_command():
+    """Commande d'installation adaptée à l'interpréteur QUI TOURNE.
+
+    C'est lui qui devra importer Textual, pas le python du système : viser
+    `sys.executable` évite d'installer un paquet distribution que le venv ne
+    verrait jamais. Hors venv, « --user » contourne le refus des
+    distributions dont l'environnement est « externally managed » (PEP 668).
+    """
+    cmd = [sys.executable, "-m", "pip", "install", "textual"]
+    if not in_venv():
+        cmd.insert(4, "--user")
+    return cmd
+
+
+def ensure(prompt=True, ask=input):
+    """Textual disponible ? Sinon proposer de l'installer. Renvoie un booléen.
+
+    `prompt=False` se contente de constater — pour les appels qui ne peuvent
+    pas poser de question. `ask` est injectable pour les tests.
+    """
+    if available():
+        return True
+    print(f"\n⚠  {t('Textual is required for this screen.')}")
+    if not prompt:
+        return False
+    answer = ask(t("Install it now? (Y/n): ")).strip().lower()
+    if answer and answer not in ("y", "yes", "o", "oui"):
+        return False
+
+    cmd = install_command()
+    print(f"  {t('Will execute:')} {' '.join(cmd)}")
+    try:
+        status = subprocess.run(cmd).returncode
+    except (OSError, subprocess.SubprocessError) as exc:
+        print(f"  ⚠ {exc}")
+        return False
+
+    # Un import négatif est mémorisé : sans purge du cache, Textual resterait
+    # « absent » pour ce processus alors qu'il vient d'être installé.
+    importlib.invalidate_caches()
+    if available():
+        print(f"✅ {t('Textual is installed.')}")
+        return True
+    print(f"  ⚠ {t('Installation finished but textual is still missing.')}")
+    if status:
+        print(f"    {t('pip exited with')} {status}")
+    print(f"    {t('Your distribution may package it as python3-textual.')}")
+    return False

script/todo/todo.py

@@ -584,12 +584,15 @@ class TODO:
         et la position du curseur sont restaurés) ou de quitter."""
         from script.todo.todo_telemetry import run_tui
 
+        from script.todo import textual_setup
+
+        if not textual_setup.ensure():
+            return
         state = None
         while True:
             try:
                 result = run_tui(state=state)
             except ImportError:
-                print(t("Install textual for the telemetry TUI (pip)."))
                 return
             if not result:
                 return
@@ -1843,10 +1846,13 @@ class TODO:
         Tout vient de l'historique tenu par le moniteur d'installation
         (.venv.erplibre/qemu_install_stats.json) et de l'état libvirt courant.
         """
+        # Cet écran ne lit que des fichiers : il n'a pas besoin de Textual,
+        # contrairement au dashboard du même module. Un échec d'import est
+        # donc un vrai problème de module, pas une dépendance manquante.
         try:
             from script.todo import qemu_install_monitor as mon
-        except ImportError:
+        except ImportError as exc:
-            print(t("Install textual for the dashboard (pip)."))
+            print(f"{t('Command failed: ')}{exc}")
             return
 
         while True:
@@ -2242,7 +2248,10 @@ class TODO:
         try:
             mon.run_monitor(run["manifest"])
         except ImportError:
-            print(t("Install textual for the dashboard (pip)."))
+            from script.todo import textual_setup
+
+            if textual_setup.ensure():
+                mon.run_monitor(run["manifest"])
         except Exception as exc:
             print(f"{t('Command failed: ')}{exc}")
 
@@ -4278,8 +4287,11 @@ class TODO:
             run_monitor(manifest)
         except ImportError:
             # textual absent : les installs tournent déjà (détachées), on ne
-            # plante pas — on indique juste où sont les logs.
+            # plante donc pas — on propose de l'installer pour rouvrir.
-            print(f"  {t('Install textual for the dashboard (pip).')}")
+            from script.todo import textual_setup
+
+            if textual_setup.ensure():
+                run_monitor(manifest)
         print(
             f"\n{t('Monitor closed. Installs keep running in the background.')}"
         )
@@ -4916,16 +4928,16 @@ class TODO:
     def _qemu_deploy_form(self, mod, dry_run):
         """Ouvre le formulaire TUI. Renvoie la spec, None si annulé, ou {}
         pour retomber sur les invites en ligne (textual absent)."""
+        from script.todo import textual_setup
+
+        if not textual_setup.ensure():
+            return {}
         try:
             from script.todo.qemu_deploy_form import run_deploy_form
-        except ImportError:
+
-            print(t("Install textual for the dashboard (pip)."))
+            ctx = self._qemu_form_context(mod)
-            return {}
-        ctx = self._qemu_form_context(mod)
-        try:
             spec = run_deploy_form(ctx)
         except ImportError:
-            print(t("Install textual for the dashboard (pip)."))
             return {}
         if not spec:
             print(t("Cancelled."))
@@ -5255,12 +5267,15 @@ class TODO:
     def _qemu_deploy_jobs_tui(self, jobs, workers):
         """Même chose, en blocs repliables Textual. Renvoie None si textual
         manque, pour que l'appelant retombe sur la sortie texte."""
+        from script.todo import textual_setup
+
+        if not textual_setup.ensure():
+            return None
         try:
             from script.todo.qemu_deploy_form import run_deploy_progress
 
             return run_deploy_progress(jobs, workers)
         except ImportError:
-            print(f"  {t('Install textual for the dashboard (pip).')}")
             return None
 
     def _qemu_run_spec(self, spec):

script/todo/todo_i18n.py

@@ -2118,9 +2118,29 @@ TRANSLATIONS = {
         "fr": "Échec de la commande : ",
         "en": "Command failed: ",
     },
-    "Install textual for the telemetry TUI (pip).": {
+    "Textual is required for this screen.": {
-        "fr": "Installez textual pour le TUI de télémétrie (pip).",
+        "fr": "Textual est nécessaire pour cet écran.",
-        "en": "Install textual for the telemetry TUI (pip).",
+        "en": "Textual is required for this screen.",
+    },
+    "Install it now? (Y/n): ": {
+        "fr": "L'installer maintenant ? (O/n, défaut : oui) : ",
+        "en": "Install it now? (Y/n, default: yes): ",
+    },
+    "Textual is installed.": {
+        "fr": "Textual est installé.",
+        "en": "Textual is installed.",
+    },
+    "Installation finished but textual is still missing.": {
+        "fr": "Installation terminée mais textual reste introuvable.",
+        "en": "Installation finished but textual is still missing.",
+    },
+    "pip exited with": {
+        "fr": "pip a retourné",
+        "en": "pip exited with",
+    },
+    "Your distribution may package it as python3-textual.": {
+        "fr": "Votre distribution le fournit peut-être en python3-textual.",
+        "en": "Your distribution may package it as python3-textual.",
     },
     "Resize a VM disk": {
         "fr": "📐 Redimensionner le disque d'une VM",
@@ -3113,10 +3133,6 @@ TRANSLATIONS = {
         "fr": "Fichiers de log :",
         "en": "Log files:",
     },
-    "Install textual for the dashboard (pip).": {
-        "fr": "Installez textual pour le dashboard (pip).",
-        "en": "Install textual for the dashboard (pip).",
-    },
     "Parallel deployments (default:": {
         "fr": "Déploiements en parallèle (défaut :",
         "en": "Parallel deployments (default:",

script/todo/todo_upgrade.py

@@ -507,12 +507,15 @@ class TodoUpgrade:
     def resume_tui(ctx):
         """Resume screen as a TUI. Returns the SAME answer strings as the
         prompt, or None when textual is missing (fall back to the prompt)."""
+        from script.todo import textual_setup
+
+        if not textual_setup.ensure():
+            return None
         try:
             from script.todo.migration_form import run_resume_tui
 
             return run_resume_tui(ctx)
         except ImportError:
-            print(t("Install textual for the dashboard (pip)."))
             return None
 
     @staticmethod