fix(dashboard): catch single-line matplotlib artist dicts alongside a figure

The multi-line branch of the discard heuristic already caught boxplot's dict-of-Line2D repr when IPython pretty-prints it across lines, but a short dict small enough to stay on one line (e.g. a single-entry boxplot/hist result) fell into the single-line branch, which only matched bracket wrappers starting with <, (, or [ — not {. Extend the single-line case to also discard a {...} repr that references a matplotlib object.

Author: cderv

src/core/jupyter/jupyter.ts

@@ -1774,7 +1774,8 @@ export function isDiscardableTextExecuteResult(
             // numeric coordinate (Text(0.5, ...)), unlike other libraries' Text
             const first = textPlain[0].trim();
             return /^([<(\[]).*?([>)\]])$/.test(first) ||
-              /^Text\([-\d]/.test(first);
+              /^Text\([-\d]/.test(first) ||
+              (first.startsWith("{") && first.includes("<matplotlib."));
           } else {
             // multi-line reprs that are collections of matplotlib artists, e.g.
             // the dict of Line2D returned by boxplot(). Only suppress when a

tests/unit/jupyter/discardable-text.test.ts

@@ -31,6 +31,9 @@ const boxplotDict = [
   " 'fliers': [<matplotlib.lines.Line2D at 0x17685b55010>],\n",
   " 'means': []}",
 ];
+// A single-line dict of matplotlib artists (small enough that IPython does not
+// pretty-print it across lines). Unambiguous plotting noise.
+const singleLineDict = ["{'line': <matplotlib.lines.Line2D at 0x1407>}"];
 const titleText = ["Text(0.5, 1.0, 'Test')"];
 const axesRepr = ["<Axes: title={'center': 'Test'}>"];
 const line2DRepr = ["<matplotlib.lines.Line2D at 0x14071bc7e00>"];
@@ -69,6 +72,11 @@ unitTest(
       true,
       "bare Line2D repr should be discarded",
     );
+    assertEquals(
+      isDiscardableTextExecuteResult(execResult(singleLineDict), true),
+      true,
+      "single-line dict of matplotlib artists should be discarded",
+    );
 
     // Gate: with no image in the cell, nothing here is discarded — a cell
     // that only echoed these values (no figure) must keep them.