yeast: Annotate children outside parent source ranges

In some cases (I'm looking at you, access_declaration) we link up things
like the modifier of an accessor to a node that lives _outside_ of the
declaration itself. Previously this was treated as an error (and the
"fix" was to extend the source ranges), but this lead to some weird
source skeletons in the output. Instead, we now allow the source of a
node to be anywhere (within reason -- it has to be inside the file, and
properly UTF-8 aligned), and simply add a trailing ` (external)` to the
source annotation. Thus, the fields containing these values do not
appear in the source skeleton for the node in question.

Author: tausbn

shared/yeast/doc/yeast.md

@@ -292,6 +292,17 @@ return_expr source="return ⟨value⟩"
     call_expr source="⟨callee⟩(⟨argument⟩)"
 ```
 
+Children outside the node's source range retain their own locations and are
+annotated where they are printed rather than being treated as errors:
+
+```text
+accessor_declaration source="⟨accessor_kind⟩"
+  name_node: identifier "value" source="value" (external)
+```
+
+Node and child ranges are still validated against the source text and UTF-8
+boundaries.
+
 ### Optional fields (`?`)
 
 A `?` on a field's value makes that field fallible. If a `#{expr}` anywhere

shared/yeast/src/dump.rs

@@ -51,7 +51,7 @@ pub fn dump_ast(ast: &Ast, root: Id, source: &str) -> String {
 
 pub fn dump_ast_with_options(ast: &Ast, root: Id, source: &str, options: &DumpOptions) -> String {
     let mut out = String::new();
-    dump_node(ast, root, source, options, 0, None, &mut out);
+    dump_node(ast, root, source, options, 0, None, false, &mut out);
     out
 }
 
@@ -86,6 +86,7 @@ pub fn dump_ast_with_type_errors_and_options(
             expected: None,
             parent_field: None,
         }),
+        false,
         &mut out,
     );
     out
@@ -195,6 +196,7 @@ fn dump_node(
     options: &DumpOptions,
     indent: usize,
     type_check: Option<TypeCheckContext<'_>>,
+    external_to_parent: bool,
     out: &mut String,
 ) {
     let node = match ast.get_node(id) {
@@ -232,6 +234,9 @@ fn dump_node(
 
     if options.show_abridged_source {
         write_source_skeleton(ast, node, source, out);
+        if external_to_parent {
+            write!(out, " (external)").unwrap();
+        }
     }
 
     if let Some(context) = type_check {
@@ -300,9 +305,18 @@ fn dump_node(
             write!(out, "{prefix}  {field_name}:").unwrap();
             // Inline single child
             let child = ast.get_node(children[0]);
+            let external = child.is_some_and(|child| is_external_child(node, child));
             if child.is_some_and(is_leaf) {
                 write!(out, " ").unwrap();
-                dump_node_inline(ast, children[0], source, options, child_type_check, out);
+                dump_node_inline(
+                    ast,
+                    children[0],
+                    source,
+                    options,
+                    child_type_check,
+                    external,
+                    out,
+                );
             } else {
                 writeln!(out).unwrap();
                 dump_node(
@@ -312,19 +326,24 @@ fn dump_node(
                     options,
                     indent + 2,
                     child_type_check,
+                    external,
                     out,
                 );
             }
         } else {
             writeln!(out, "{prefix}  {field_name}:").unwrap();
             for &child_id in children {
+                let external = ast
+                    .get_node(child_id)
+                    .is_some_and(|child| is_external_child(node, child));
                 dump_node(
                     ast,
                     child_id,
                     source,
                     options,
                     indent + 2,
                     child_type_check,
+                    external,
                     out,
                 );
             }
@@ -365,13 +384,15 @@ fn dump_node(
         for &child_id in children {
             if let Some(child) = ast.get_node(child_id) {
                 if child.is_named() {
+                    let external = is_external_child(node, child);
                     dump_node(
                         ast,
                         child_id,
                         source,
                         options,
                         indent + 1,
                         child_type_check,
+                        external,
                         out,
                     );
                 }
@@ -387,6 +408,7 @@ fn dump_node_inline(
     source: &str,
     options: &DumpOptions,
     type_check: Option<TypeCheckContext<'_>>,
+    external_to_parent: bool,
     out: &mut String,
 ) {
     let node = match ast.get_node(id) {
@@ -419,6 +441,9 @@ fn dump_node_inline(
 
     if options.show_abridged_source {
         write_source_skeleton(ast, node, source, out);
+        if external_to_parent {
+            write!(out, " (external)").unwrap();
+        }
     }
 
     if let Some(context) = type_check {
@@ -457,6 +482,13 @@ fn node_source_range(node: &Node) -> Option<crate::Range> {
     }
 }
 
+fn is_external_child(parent: &Node, child: &Node) -> bool {
+    let (Some(parent), Some(child)) = (node_source_range(parent), node_source_range(child)) else {
+        return false;
+    };
+    child.start_byte < parent.start_byte || child.end_byte > parent.end_byte
+}
+
 fn source_skeleton(ast: &Ast, node: &Node, source: &str) -> SourceSkeleton {
     let Some(parent) = node_source_range(node) else {
         return SourceSkeleton::Missing;
@@ -494,10 +526,7 @@ fn source_skeleton(ast: &Ast, node: &Node, source: &str) -> SourceSkeleton {
                 ));
             }
             if child.start < parent.start || child.end > parent.end {
-                return SourceSkeleton::Invalid(format!(
-                    "child range {}..{} is outside node range {}..{}",
-                    child.start, child.end, parent.start, parent.end
-                ));
+                continue;
             }
             if child.start == child.end {
                 continue;
@@ -613,12 +642,6 @@ mod tests {
     #[test]
     fn source_skeleton_validates_empty_child_ranges() {
         let cases = [
-            (
-                "abcdef",
-                range(0, 3),
-                range(4, 4),
-                "child range 4..4 is outside node range 0..3",
-            ),
             (
                 "abcdef",
                 range(0, 6),
@@ -640,6 +663,13 @@ mod tests {
                 "unexpected dump: {dump}"
             );
         }
+
+        let dump = dump_with_children("abcdef", range(0, 3), &[("marker", range(4, 4))]);
+        assert!(dump.starts_with("parent source=\"abc\"\n"));
+        assert!(
+            dump.contains("marker: child source=\"\" (external)\n"),
+            "unexpected dump: {dump}"
+        );
     }
 
     #[test]
@@ -667,12 +697,15 @@ mod tests {
     }
 
     #[test]
-    fn source_skeleton_reports_children_outside_the_parent() {
+    fn source_skeleton_marks_children_outside_the_parent() {
         let source = "abcdefghi";
         let dump = dump_with_children(source, range(0, 6), &[("child", range(7, 9))]);
 
-        assert!(dump
-            .starts_with("parent source=<invalid: child range 7..9 is outside node range 0..6>\n"));
+        assert!(dump.starts_with("parent source=\"abcdef\"\n"));
+        assert!(
+            dump.contains("  child source=\"hi\" (external)\n"),
+            "unexpected dump: {dump}"
+        );
     }
 }