Fixing bug where AttributedSpans.collapseSpans could throw a StateError

Author: jmatth

attributed_text/lib/src/attributed_spans.dart

@@ -897,7 +897,7 @@ class AttributedSpans {
       }
     }
 
-    if (collapsedSpans.last.end < contentLength) {
+    if (collapsedSpans.isEmpty || collapsedSpans.last.end < contentLength) {
       // The last span committed during the loop does not reach the end of the requested content range. We either ran
       // out of markers or the remaining markers are outside the content range. In both cases the value in currentSpan
       // should already have the correct start, end, and attributions values to cover the remaining content.

attributed_text/test/attributed_spans_test.dart

@@ -486,19 +486,46 @@ void main() {
         expect(collapsedSpans.first.attributions, isEmpty);
       });
 
-      test('single continuous attribution', () {
-        final collapsedSpans = AttributedSpans(
+      group('single continuous attribution', () {
+        final spans = AttributedSpans(
           attributions: [
             const SpanMarker(attribution: ExpectedSpans.bold, offset: 0, markerType: SpanMarkerType.start),
             const SpanMarker(attribution: ExpectedSpans.bold, offset: 16, markerType: SpanMarkerType.end),
           ],
-        ).collapseSpans(contentLength: 16);
+        );
 
-        expect(collapsedSpans.length, 1);
-        expect(collapsedSpans.first.start, 0);
-        expect(collapsedSpans.first.end, 16);
-        expect(collapsedSpans.first.attributions.length, 1);
-        expect(collapsedSpans.first.attributions.first, ExpectedSpans.bold);
+        test('collapse at span end', () {
+          final collapsedSpans = spans.collapseSpans(contentLength: 16);
+
+          expect(collapsedSpans.length, 1);
+          expect(collapsedSpans.first.start, 0);
+          expect(collapsedSpans.first.end, 16);
+          expect(collapsedSpans.first.attributions.length, 1);
+          expect(collapsedSpans.first.attributions.first, ExpectedSpans.bold);
+        });
+
+        test('collapse before span end', () {
+          final collapsedSpans = spans.collapseSpans(contentLength: 10);
+
+          expect(collapsedSpans.length, 1);
+          expect(collapsedSpans.first.start, 0);
+          expect(collapsedSpans.first.end, 10);
+          expect(collapsedSpans.first.attributions.length, 1);
+          expect(collapsedSpans.first.attributions.first, ExpectedSpans.bold);
+        });
+
+        test('collapse after span end', () {
+          final collapsedSpans = spans.collapseSpans(contentLength: 20);
+
+          expect(collapsedSpans.length, 2);
+          expect(collapsedSpans[0].start, 0);
+          expect(collapsedSpans[0].end, 16);
+          expect(collapsedSpans[0].attributions.length, 1);
+          expect(collapsedSpans[0].attributions.first, ExpectedSpans.bold);
+          expect(collapsedSpans[1].start, 16);
+          expect(collapsedSpans[1].end, 20);
+          expect(collapsedSpans[1].attributions, isEmpty);
+        });
       });
 
       test('single fractured attribution', () {