Limit the number of bins for histograms to avoid crashes. (#655)

crates/ark/src/data_explorer/histogram.rs

@@ -632,4 +632,29 @@ mod tests {
             );
         })
     }
+
+    #[test]
+    fn test_limit_bins() {
+        // Regression test for https://github.com/posit-dev/positron/issues/5744
+        r_task(|| {
+            let column = harp::parse_eval_global("rep(c(1:10, 5e7), 10)").unwrap();
+
+            let hist = profile_histogram(
+                column.sexp,
+                &ColumnHistogramParams {
+                    method: ColumnHistogramParamsMethod::FreedmanDiaconis,
+                    // If num_bins wasn't set to 10, that would generate almost 200k bins
+                    num_bins: 10,
+                    quantiles: None,
+                },
+                &default_options(),
+            )
+            .unwrap();
+
+            assert_match!(hist, ColumnHistogram { bin_edges, bin_counts, .. } => {
+                assert_eq!(bin_edges.len(), 11);
+                assert_eq!(bin_counts.len(), 10);
+            });
+        })
+    }
 }

crates/ark/src/modules/positron/r_data_explorer.R

@@ -519,5 +519,10 @@ histogram_num_bins <- function(x, method, fixed_num_bins) {
         }
     }
 
+    # Honor the maximum amount of bins requested by the front-end.
+    if (!is.null(fixed_num_bins) && num_bins > fixed_num_bins) {
+        num_bins <- fixed_num_bins
+    }
+
     as.integer(num_bins)
 }