blueslip: Pass the Error around, rather than re-creating a dummy one.

web/src/blueslip.ts

@@ -122,23 +122,6 @@ export function error(
     // fatal error even in production, use throw new Error(…) instead.
 }
 
-export function exception_msg(
-    ex: Error & {
-        // Unsupported properties available on some browsers
-        fileName?: string;
-        lineNumber?: number;
-    },
-): string {
-    let message = ex.message;
-    if (ex.fileName !== undefined) {
-        message += " at " + ex.fileName;
-        if (ex.lineNumber !== undefined) {
-            message += `:${ex.lineNumber}`;
-        }
-    }
-    return message;
-}
-
 // Install a window-wide onerror handler in development to display the stacktraces, to make them
 // hard to miss
 if (page_params.development_environment) {
@@ -153,6 +136,6 @@ if (page_params.development_environment) {
             return;
         }
 
-        void blueslip_stacktrace.display_stacktrace(exception_msg(ex), ex.stack);
+        void blueslip_stacktrace.display_stacktrace(ex);
     });
 }

web/src/blueslip_stacktrace.ts

@@ -24,6 +24,23 @@ type CleanStackFrame = {
     context?: NumberedLine[];
 };
 
+export function exception_msg(
+    ex: Error & {
+        // Unsupported properties available on some browsers
+        fileName?: string;
+        lineNumber?: number;
+    },
+): string {
+    let message = ex.message;
+    if (ex.fileName !== undefined) {
+        message += " at " + ex.fileName;
+        if (ex.lineNumber !== undefined) {
+            message += `:${ex.lineNumber}`;
+        }
+    }
+    return message;
+}
+
 export function clean_path(full_path?: string): string | undefined {
     // If the file is local, just show the filename.
     // Otherwise, show the full path starting from node_modules.
@@ -81,10 +98,7 @@ async function get_context(location: StackFrame): Promise<NumberedLine[] | undef
     }));
 }
 
-export async function display_stacktrace(error: string, stack: string): Promise<void> {
-    const ex = new Error("dummy");
-    ex.stack = stack;
-
+export async function display_stacktrace(ex: Error): Promise<void> {
     const stackframes: CleanStackFrame[] = await Promise.all(
         ErrorStackParser.parse(ex).map(async (location: StackFrame) => {
             try {
@@ -104,7 +118,12 @@ export async function display_stacktrace(error: string, stack: string): Promise<
 
     const $alert = $("<div>")
         .addClass("stacktrace")
-        .html(render_blueslip_stacktrace({error, stackframes}));
+        .html(
+            render_blueslip_stacktrace({
+                error: exception_msg(ex),
+                stackframes,
+            }),
+        );
     $(".alert-box").append($alert);
     $alert.addClass("show");
 }