Auto reload changed files

src/app/tests.rs

@@ -91,3 +91,64 @@ fn close_and_fit_sizes_the_card_and_closes_the_editor() {
     );
     assert_eq!(app.doc.undo_label(), Some("Fit to text"));
 }
+
+/// A file node follows its file when something else writes it.
+#[test]
+fn a_card_follows_a_file_changed_outside_the_editor() -> Result<(), Box<dyn std::error::Error>> {
+    let dir =
+        std::env::temp_dir().join(format!("jsoncanvas-outside-{}", crate::model::random_id()));
+    std::fs::create_dir_all(&dir)?;
+    let path = dir.join("note.md");
+    std::fs::write(&path, "before the change\n")?;
+
+    let mut canvas = Canvas::default();
+    canvas.nodes.push(Node::new(
+        "f",
+        NodeKind::File {
+            file: path.display().to_string(),
+            subpath: None,
+        },
+        0,
+        0,
+        400,
+        300,
+    ));
+    let mut harness = Harness::builder()
+        .with_size(egui::vec2(1200.0, 900.0))
+        .build_eframe(|cc| App::new(cc, None));
+    harness.state_mut().doc = Document::new();
+    harness.state_mut().doc.canvas = canvas;
+    harness.run();
+    assert!(harness.query_by_label("before the change").is_some());
+
+    // Another program writes the file while the canvas is open.
+    std::fs::write(&path, "after the change\n")?;
+    // The check is on a timer; this is the same as waiting for it to come up.
+    harness.state_mut().last_file_check = f64::MIN;
+    harness.run();
+
+    assert!(harness.query_by_label("after the change").is_some());
+    assert!(
+        harness.query_by_label("before the change").is_none(),
+        "the card kept showing the text the file no longer holds"
+    );
+
+    // With an edit made here the card keeps it, and says the file moved on.
+    harness
+        .state_mut()
+        .view
+        .files
+        .set(&path, "edited here\n".to_owned());
+    std::fs::write(&path, "changed again, elsewhere\n")?;
+    harness.state_mut().last_file_check = f64::MIN;
+    harness.run();
+
+    assert!(harness.query_by_label("edited here").is_some());
+    assert!(
+        harness.query_by_label("\u{26a0}").is_some(),
+        "the card said nothing about the file changing under the edit"
+    );
+
+    std::fs::remove_dir_all(&dir)?;
+    Ok(())
+}