test(engine): Content-Aware Fill with an empty sampling area is refused and changes nothing (#6532)

crates/engine/src/edit_menu_cmds/tests.rs

@@ -105,10 +105,15 @@ fn blob_session(depth: u32) -> Session {
 fn content_aware_fill_huge_area_neither_panics_nor_wraps() {
     let mut s = blob_session(8);
     // `[1e30, 0, 1e30, 10]` overflowed the i32 additions in the area parser (a debug-build
-    // panic, a garbage sampling window in release); the additions saturate now, so this is
-    // simply a whole-canvas window.
-    let r = s.execute("edit.contentAwareFill", json!({"sampling": "custom", "area": [1e30, 0.0, 1e30, 10.0], "colorAdaptation": "none"})).unwrap();
-    assert!(r["filled"].as_u64().unwrap() > 100);
+    // panic, a garbage sampling window in release); the additions saturate now, so the area lies
+    // wholly right of the canvas: nothing to sample, which is an error, not a black fill (#6532).
+    let before = s.active().unwrap().doc.clone();
+    let past = s.active().unwrap().history.past_len();
+    let err = s.execute("edit.contentAwareFill", json!({"sampling": "custom", "area": [1e30, 0.0, 1e30, 10.0], "colorAdaptation": "none"})).unwrap_err();
+    assert!(err.to_string().contains("nothing to sample from"), "{err}");
+    let st = s.active().unwrap();
+    assert!(std::sync::Arc::ptr_eq(&before, &st.doc), "the document changed");
+    assert_eq!(st.history.past_len(), past, "a history step was recorded");
     // A malformed area names the problem instead of silently falling back.
     for area in [json!([0.0, 0.0, null, 10.0]), json!([0.0, 0.0, 10.0]), json!("nope")] {
         let err = s.execute("edit.contentAwareFill", json!({"sampling": "custom", "area": area})).unwrap_err();
@@ -312,6 +317,23 @@ fn content_aware_fill_takes_the_workspace_edits() {
     assert!(r["filled"].as_u64().unwrap() > 2800);
 }
 
+/// #6532: a sampling area with no pixels outside the fill area is refused instead of filling it
+/// black, and leaves the document untouched; any margin past the selection fills.
+#[test]
+fn content_aware_fill_with_nothing_to_sample_is_refused() {
+    let mut s = blob_session(8);
+    let before = px(&s, 30, 22);
+    let revision = s.active().unwrap().revision;
+    for p in [json!({"sampling": "rectangular", "margin": 0}), json!({"sampling": "custom", "area": [28, 18, 4, 4]})] {
+        let e = s.execute("edit.contentAwareFill", p.clone()).unwrap_err().to_string();
+        assert!(e.contains("nothing to sample from"), "{p}: {e}");
+        assert_eq!(px(&s, 30, 22), before, "{p}: nothing was filled");
+        assert_eq!(s.active().unwrap().revision, revision, "{p}: no history step");
+    }
+    s.execute("edit.contentAwareFill", json!({"sampling": "rectangular", "margin": 1})).unwrap();
+    assert_ne!(px(&s, 30, 22), before, "the red blob is filled from around the selection");
+}
+
 #[test]
 fn content_aware_fill_outputs_and_sampling() {
     let mut s = blob_session(8);