.ai save: the editing copy warns about missing placed files

A .ai saved with pdfCompatible false resolved placed files for the
editing copy but dropped the warnings for the ones it couldn't find,
so a missing placed file was written as its preview without a warning.
The save now keeps those warnings.

crates/engine/src/cmd/fileio/save.rs

@@ -637,17 +637,21 @@ pub(super) fn encode_ai(cmd: &str, f: &Format, doc: &Document, p: &Value) -> Res
         }
         // The art with placed files resolved as the pages draw them, also when the pages are blank.
         let resolved;
-        let art: &Document = if pdf_compatible {
-            &pages
+        let (art, mut resolved_warnings): (&Document, Vec<String>) = if pdf_compatible {
+            (&pages, Vec::new())
         } else {
-            resolved = crate::cmd::place::document::full_documents(&edited).0;
-            &resolved
+            let (d, w) = crate::cmd::place::document::full_documents(&edited);
+            resolved = d;
+            (&resolved, w)
         };
         let o = vectorcraft_eps::AiEditingOptions {
             title: doc.title.clone(),
             created: doc.metadata.created.or_else(vectorcraft_doc::metadata::output_time),
         };
-        vectorcraft_eps::ai_private_data(art, &o).map(Some).map_err(|e| bad(cmd, e))
+        let (data, lost) = vectorcraft_eps::ai_private_data(art, &o).map_err(|e| bad(cmd, e))?;
+        // Placed files that weren't found are written as their previews here too.
+        resolved_warnings.extend(lost);
+        Ok(Some((data, resolved_warnings)))
     };
     let (bytes, mut warnings) = super::pdf::encode_carrying(cmd, &pages, &params, native, private)?;
     warnings.extend(placed_warnings);

crates/engine/src/tests/placed_document.rs

@@ -288,6 +288,30 @@ fn ai_export_public_aliases_preserve_missing_placed_links() {
     }
 }
 
+/// The `.ai` editing copy for other apps draws a missing placed file as its preview, with the
+/// pages or without them, and says so.
+#[test]
+fn ai_editing_copy_warns_about_missing_placed_files() {
+    let dir = Folder::new("placed-ai-editing-copy-missing");
+    let src = dir.file("logo.vectorcraft");
+    star_source(&src, "placed-ai-editing-copy-missing-unique");
+    let mut s = session();
+    place(&mut s, &src);
+    let parent = dir.file("parent.vectorcraft");
+    save(&mut s, &parent);
+    std::fs::remove_file(&src).unwrap();
+    open(&mut s, &parent);
+    let doc = &s.doc().unwrap().doc;
+    let (_, missing) = cmd::place::document::full_documents(doc);
+    assert!(!missing.is_empty());
+    for compatible in [true, false] {
+        let enc = cmd::fileio::encode_all(doc, "ai", &json!({"pdfCompatible": compatible})).unwrap();
+        for w in &missing {
+            assert!(enc.warnings.contains(w), "pdfCompatible {compatible}: {w:?} not in {:?}", enc.warnings);
+        }
+    }
+}
+
 /// Include Linked Files must retain relinkable objects when only their previews are available.
 #[test]
 fn native_included_links_keep_missing_placed_documents_editable() {