Include token in subgraph even if not covered by segmentation node

CHANGELOG.md

@@ -5,6 +5,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- Include token in subgraph even if not covered by segmentation node #334.
+
 ## [4.1.1] - 2026-01-13
 
 ### Added

graphannis/src/annis/db/corpusstorage/subgraph.rs

@@ -183,12 +183,12 @@ fn get_left_right_token_with_offset_with_segmentation(
         }
     })?;
 
-    let left_seg = *covering_segmentation_nodes
-        .first()
-        .ok_or(GraphAnnisError::NoCoveredTokenForSubgraph)?;
-    let right_seg = *covering_segmentation_nodes
-        .last()
-        .ok_or(GraphAnnisError::NoCoveredTokenForSubgraph)?;
+    let (left_seg, right_seg) = match covering_segmentation_nodes[..] {
+        // If none of the covered tokens are covered by a segmentation node, return without context
+        [] => return Ok((left_most_covered_token, right_most_covered_token)),
+        [only] => (only, only),
+        [left, .., right] => (left, right),
+    };
 
     // The context might be larger than the actual document, try to get the
     // largest possible context

graphannis/src/annis/db/corpusstorage/tests.rs

@@ -286,7 +286,7 @@ fn create_simple_graph(cs: &mut CorpusStorage) {
 }
 
 #[test]
-fn subgraphs_simple() {
+fn subgraph_simple() {
     let tmp = tempfile::tempdir().unwrap();
     let mut cs = CorpusStorage::with_auto_cache_size(tmp.path(), false).unwrap();
 
@@ -440,7 +440,7 @@ fn subgraphs_simple() {
 }
 
 #[test]
-fn subgraphs_non_overlapping_regions() {
+fn subgraph_non_overlapping_regions() {
     let tmp = tempfile::tempdir().unwrap();
     let mut cs = CorpusStorage::with_auto_cache_size(tmp.path(), false).unwrap();
 
@@ -573,7 +573,7 @@ fn subgraphs_non_overlapping_regions() {
 }
 
 #[test]
-fn subgraphs_non_overlapping_regions_one_context_zero() {
+fn subgraph_non_overlapping_regions_one_context_zero() {
     let tmp = tempfile::tempdir().unwrap();
     let mut cs = CorpusStorage::with_auto_cache_size(tmp.path(), false).unwrap();
 
@@ -674,7 +674,7 @@ fn subgraphs_non_overlapping_regions_one_context_zero() {
 }
 
 #[test]
-fn subgraphs_non_overlapping_regions_no_context_tokens_specified_out_of_order() {
+fn subgraph_non_overlapping_regions_no_context_tokens_specified_out_of_order() {
     let tmp = tempfile::tempdir().unwrap();
     let mut cs = CorpusStorage::with_auto_cache_size(tmp.path(), false).unwrap();
 
@@ -999,6 +999,59 @@ fn subgraph_with_segmentation_and_gap() {
             .unwrap()
             .is_some()
     );
+
+    // Get the context for the token in the gap using the norm segmentation
+    let g = cs
+        .subgraph(
+            &corpus_name,
+            vec!["SegmentationWithGaps/doc01#tok_13".to_string()],
+            0,
+            0,
+            Some("norm".to_string()),
+        )
+        .unwrap();
+    // Check that the token is included even though it is not covered by a segmentation node
+    assert!(
+        g.get_node_annos()
+            .get_node_id_from_name("SegmentationWithGaps/doc01#tok_13")
+            .unwrap()
+            .is_some()
+    );
+}
+
+#[test]
+fn subgraph_with_node_spanning_multiple_segmentation_nodes() {
+    let tmp = tempfile::tempdir().unwrap();
+    let cs = CorpusStorage::with_auto_cache_size(tmp.path(), false).unwrap();
+
+    let mut g = GraphUpdate::new();
+    example_generator::create_multiple_segmentations(&mut g, "root/doc1");
+
+    cs.apply_update("root", &mut g).unwrap();
+
+    let graph = cs
+        .subgraph(
+            "root",
+            vec!["root/doc1#b3".to_string()],
+            0,
+            0,
+            Some("a".to_string()),
+        )
+        .unwrap();
+    assert!(
+        graph
+            .get_node_annos()
+            .get_node_id_from_name("root/doc1#a2")
+            .unwrap()
+            .is_some()
+    );
+    assert!(
+        graph
+            .get_node_annos()
+            .get_node_id_from_name("root/doc1#a3")
+            .unwrap()
+            .is_some()
+    );
 }
 
 #[test]