fix(frontend,application,backend,web-server,infrastructure): le set de couleurs projet s'applique à tous les projets — #316 (QA verte)

Cause: update_project_settings remplaçait tout ProjectSettings avec la
seule couleur fournie — champ absent et null indistinguables — et des
réponses de chargement/sauvegarde obsolètes d'un projet précédent
pouvaient réafficher/écraser la couleur lors d'un changement de projet
rapide, d'où l'impression que la couleur ne prenait pas sur tous les
projets.

- DTO tri-état (absent = inchangé, null = défaut produit) avec
  Deserialize manuel et use case de mise à jour partielle du champ
  theme_color; commandes Tauri et web-server alignées sur le même
  contrat.
- Garde-fous de course frontend: séquences load/save + révision thème
  par projet (pub/sub onProjectThemeChanged) dans ProjectSettingsPanel,
  garde de révision de focus dans ViewWindow.
- Tests: infrastructure settings, contrats web-server (inchangé/reset),
  ProjectSettingsPanel, ViewWindow, projects.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

crates/app-tauri/src/commands.rs

@@ -855,7 +855,7 @@ pub async fn read_project_settings(
         .map_err(Into::into)
 }
 
-/// Validates and replaces project-owned settings.
+/// Validates and updates project-owned settings.
 #[tauri::command]
 pub async fn update_project_settings(
     request: UpdateProjectSettingsRequestDto,
@@ -864,12 +864,12 @@ pub async fn update_project_settings(
     let project = resolve_project(&request.project_id, &state).await?;
     let theme_color = request
         .theme_color
-        .map(domain::ThemeColor::new)
+        .map(|value| value.map(domain::ThemeColor::new).transpose())
         .transpose()
         .map_err(|message| ErrorDto::from(AppError::Invalid(message)))?;
     state
         .update_project_settings
-        .execute(&project, domain::ProjectSettings { theme_color })
+        .execute(&project, theme_color)
         .await
         .map(Into::into)
         .map_err(Into::into)

crates/application/src/settings.rs

@@ -1,7 +1,9 @@
 //! Read/update use cases for global and project settings.
 
 use crate::AppError;
-use domain::{IdeaUserSettings, Project, ProjectSettings, ProjectSettingsStore, UserSettingsStore};
+use domain::{
+    IdeaUserSettings, Project, ProjectSettings, ProjectSettingsStore, ThemeColor, UserSettingsStore,
+};
 use std::sync::Arc;
 
 /// Reads global machine-local user settings.
@@ -50,7 +52,7 @@ impl ReadProjectSettings {
         self.store.load(&project.root).await.map_err(Into::into)
     }
 }
-/// Replaces the settings owned by one project.
+/// Updates the settings owned by one project.
 pub struct UpdateProjectSettings {
     store: Arc<dyn ProjectSettingsStore>,
 }
@@ -60,13 +62,20 @@ impl UpdateProjectSettings {
     pub fn new(store: Arc<dyn ProjectSettingsStore>) -> Self {
         Self { store }
     }
-    /// Persists and returns the accepted project settings.
+    /// Applies the supplied fields and returns the accepted project settings.
+    ///
+    /// An absent outer option leaves the colour unchanged; an explicit inner
+    /// `None` restores the product fallback.
     pub async fn execute(
         &self,
         project: &Project,
-        settings: ProjectSettings,
+        theme_color: Option<Option<ThemeColor>>,
     ) -> Result<ProjectSettings, AppError> {
-        self.store.save(&project.root, &settings).await?;
+        let mut settings = self.store.load(&project.root).await?;
+        if let Some(theme_color) = theme_color {
+            settings.theme_color = theme_color;
+            self.store.save(&project.root, &settings).await?;
+        }
         Ok(settings)
     }
 }

crates/backend/src/dto.rs

@@ -3295,14 +3295,32 @@ impl From<domain::ProjectSettings> for ProjectSettingsDto {
 }
 
 /// Project settings update request.
-#[derive(Debug, Clone, Deserialize)]
-#[serde(rename_all = "camelCase")]
+#[derive(Debug, Clone)]
 pub struct UpdateProjectSettingsRequestDto {
     /// Project registry id.
     pub project_id: String,
-    /// New colour, or null to restore the product default.
-    #[serde(default)]
-    pub theme_color: Option<String>,
+    /// Missing leaves the colour unchanged; null restores the product default.
+    pub theme_color: Option<Option<String>>,
+}
+
+impl<'de> Deserialize<'de> for UpdateProjectSettingsRequestDto {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        let mut value = Value::deserialize(deserializer)?;
+        let object = value
+            .as_object_mut()
+            .ok_or_else(|| serde::de::Error::custom("expected project settings update object"))?;
+        let project_id =
+            take_required_string(object, "projectId").map_err(serde::de::Error::custom)?;
+        let theme_color = take_optional_value::<String>(object, "themeColor")
+            .map_err(serde::de::Error::custom)?;
+        Ok(Self {
+            project_id,
+            theme_color,
+        })
+    }
 }
 
 /// Request DTO for `launch_agent`.

crates/infrastructure/tests/settings.rs

@@ -62,9 +62,46 @@ async fn project_settings_missing_then_valid_round_trip() {
     };
     store.save(&tmp.root(), &settings).await.unwrap();
     assert_eq!(store.load(&tmp.root()).await.unwrap(), settings);
+    assert_eq!(
+        std::fs::read_to_string(tmp.0.join(".ideai/project-settings.json")).unwrap(),
+        "{\n  \"themeColor\": \"#12AbEF\"\n}\n"
+    );
     assert!(!tmp.0.join(".ideai/CONTEXT.md").exists());
 }
 
+#[tokio::test]
+async fn project_settings_are_isolated_and_missing_defaults_are_not_persisted() {
+    let first = TempDir::new();
+    let second = TempDir::new();
+    let store = FsProjectSettingsStore::new(fs());
+
+    store
+        .save(
+            &first.root(),
+            &ProjectSettings {
+                theme_color: Some(ThemeColor::new("#AA3366").unwrap()),
+            },
+        )
+        .await
+        .unwrap();
+
+    assert_eq!(
+        store.load(&second.root()).await.unwrap(),
+        ProjectSettings::default()
+    );
+    assert!(!second.0.join(".ideai/project-settings.json").exists());
+    assert_eq!(
+        store
+            .load(&first.root())
+            .await
+            .unwrap()
+            .theme_color
+            .as_ref()
+            .map(ThemeColor::as_str),
+        Some("#AA3366")
+    );
+}
+
 #[test]
 fn theme_color_validation_is_strict() {
     assert!(ThemeColor::new("#112233").is_ok());

crates/web-server/src/lib.rs

@@ -3920,12 +3920,12 @@ async fn invoke_update_project_settings(
     let project = resolve_project_readonly(&request.project_id, state).await?;
     let theme_color = request
         .theme_color
-        .map(domain::ThemeColor::new)
+        .map(|value| value.map(domain::ThemeColor::new).transpose())
         .transpose()
         .map_err(|message| ErrorDto::from(AppError::Invalid(message)))?;
     let output: ProjectSettingsDto = state
         .update_project_settings
-        .execute(&project, domain::ProjectSettings { theme_color })
+        .execute(&project, theme_color)
         .await
         .map_err(ErrorDto::from)?
         .into();
@@ -10627,6 +10627,26 @@ mod tests {
         .await;
         assert_eq!(status, StatusCode::OK);
         assert_eq!(saved_project["themeColor"], "#AA3366");
+
+        let (status, unchanged_project) = invoke_request_for_test(
+            Arc::clone(&state),
+            &cookie,
+            "update_project_settings",
+            json!({ "request": { "projectId": project_id } }),
+        )
+        .await;
+        assert_eq!(status, StatusCode::OK);
+        assert_eq!(unchanged_project["themeColor"], "#AA3366");
+
+        let (status, reset_project) = invoke_request_for_test(
+            Arc::clone(&state),
+            &cookie,
+            "update_project_settings",
+            json!({ "request": { "projectId": project_id, "themeColor": null } }),
+        )
+        .await;
+        assert_eq!(status, StatusCode::OK);
+        assert_eq!(reset_project["themeColor"], Value::Null);
     }
 
     #[tokio::test]