fix(windows): reopen every project window on startup (#1574)

"Reopen projects on startup" only saved window groups, so windows opened with New Window were lost. The saved session now lists every open project window (groups with their tabs and selection, single windows on their own), and the previous run's session is read before this run first overwrites it, so the startup project can't replace it before the other windows are restored.

crates/ide-workspace/src/window_groups.rs

@@ -1,6 +1,7 @@
 //! Window grouping is independent of a window's project or workspace.
 use ide_core::{IdeError, IdeResult};
 use serde::{Deserialize, Serialize};
+use std::path::PathBuf;
 
 /// Platform adapters supply the system's tab preference and active project state.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -117,6 +118,43 @@ impl WindowGroups {
     }
 }
 
+/// One entry of the window session reopened at the next start (`window-groups.json`): a
+/// window group, or a single project window (one project).
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct SavedWindows {
+    pub projects: Vec<PathBuf>,
+    /// Index into `projects` of the group's selected tab.
+    pub selected: usize,
+}
+
+/// The project windows open now, to reopen at the next start: every group with its selected
+/// tab, then each window outside a group, in the order of `windows`. `project_of` gives a
+/// window's project (`None` for the welcome screen or LightEdit). `None` while a grouped
+/// window has no project yet (a restored member still opening): keep the previous session.
+pub fn session(
+    groups: &[WindowGroup],
+    windows: &[String],
+    project_of: impl Fn(&str) -> Option<PathBuf>,
+) -> Option<Vec<SavedWindows>> {
+    let mut saved = Vec::new();
+    for group in groups {
+        let projects: Option<Vec<PathBuf>> = group.members.iter().map(|label| project_of(label)).collect();
+        let selected = group.members.iter().position(|l| l == &group.selected).unwrap_or(0);
+        saved.push(SavedWindows { projects: projects?, selected });
+    }
+    for label in windows {
+        if groups.iter().any(|g| g.members.contains(label)) {
+            continue;
+        }
+        if let Some(project) = project_of(label)
+            && !saved.iter().any(|s| s.projects.contains(&project))
+        {
+            saved.push(SavedWindows { projects: vec![project], selected: 0 });
+        }
+    }
+    Some(saved)
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -186,4 +224,28 @@ mod tests {
         groups.reorder("a", members(&["d", "c", "b", "a"])).unwrap();
         assert_eq!(groups.group("a").unwrap().members[0], "d");
     }
+
+    #[test]
+    fn the_session_keeps_groups_and_every_ungrouped_project_window() {
+        let groups = vec![WindowGroup { members: members(&["project-1", "project-2"]), selected: "project-2".into() }];
+        let windows = members(&["main", "project-1", "project-2", "project-3", "project-4"]);
+        let project_of = |label: &str| match label {
+            "main" => Some(PathBuf::from("/a")),
+            "project-1" => Some(PathBuf::from("/b")),
+            "project-2" => Some(PathBuf::from("/c")),
+            "project-3" => Some(PathBuf::from("/d")),
+            // The welcome screen or LightEdit.
+            _ => None,
+        };
+        assert_eq!(
+            session(&groups, &windows, project_of).unwrap(),
+            [
+                SavedWindows { projects: vec!["/b".into(), "/c".into()], selected: 1 },
+                SavedWindows { projects: vec!["/a".into()], selected: 0 },
+                SavedWindows { projects: vec!["/d".into()], selected: 0 },
+            ]
+        );
+        // A grouped window still opening its project: keep the previous session.
+        assert_eq!(session(&groups, &windows, |l| (l != "project-2").then(|| PathBuf::from(l))), None);
+    }
 }