Preserve authored projection content and contextual canvas selection

crates/oa-core/src/persistence.rs

@@ -341,6 +341,50 @@ pub(crate) fn check_pre6_baseline(baseline: &SemanticBaseline) -> Result<(), Fil
     }
     Ok(())
 }
+/// Frozen sources 3–6 admit opposite-layer placements and visibility references
+/// only in Traceability. Check before migration discards the advertised version;
+/// current ordinary projections may retain these records as latent presentation.
+pub(crate) fn check_pre7_diagram_admission(project: &Project) -> Result<(), FileError> {
+    let mut issues = Vec::new();
+    for diagram in project.diagrams.values() {
+        let option_issues = if diagram.projection == ProjectionKind::Traceability {
+            crate::view_options::validate_options_cross_layer(project, &diagram.view_options)
+        } else {
+            crate::view_options::validate_options(project, diagram.layer, &diagram.view_options)
+        };
+        for issue in option_issues {
+            validation::error(
+                &mut issues,
+                diagram.id,
+                "view_options",
+                issue.field,
+                issue.message,
+            );
+        }
+        for node in diagram.nodes.values() {
+            if !project.elements.get(&node.element).is_some_and(|element| {
+                diagram.projection == ProjectionKind::Traceability
+                    || element.layer() == diagram.layer
+            }) {
+                validation::error(
+                    &mut issues,
+                    node.id,
+                    "diagram_layer",
+                    "element",
+                    "Diagram nodes reference existing elements in the selected layer.",
+                );
+            }
+        }
+    }
+    if let Some(issue) = issues.into_iter().next() {
+        return Err(FileError::Model {
+            message: issue.message.clone(),
+            issues: vec![issue],
+        });
+    }
+    Ok(())
+}
+
 pub(crate) fn migrate_v5(
     mut project: Project,
     limits: crate::language::ParseLimits,
@@ -348,6 +392,7 @@ pub(crate) fn migrate_v5(
     if project.schema_version != 5 {
         return Err(FileError::Invalid("Expected schema_version 5.".into()));
     }
+    check_pre7_diagram_admission(&project)?;
     check_pre6_relations(project.relations.values())?;
     check_pre6_elements(project.elements.values())?;
     for baseline in project
@@ -420,6 +465,7 @@ pub(crate) fn migrate_v6(
     if project.schema_version != 6 {
         return Err(FileError::Invalid("Expected schema_version 6.".into()));
     }
+    check_pre7_diagram_admission(&project)?;
     reject_source7_fields(&serde_json::to_value(&project)?).map_err(FileError::Invalid)?;
     limits.check_model(&project).map_err(FileError::Limit)?;
     project.schema_version = SCHEMA_VERSION;