fix: report the message of Errors thrown in user-defined functions

src/api.js

@@ -1245,6 +1245,12 @@ Module["onRuntimeInitialized"] = function onRuntimeInitialized() {
                 sqlite3_result_null(cx);
         }
     };
+    var setFunctionError = function setFunctionError(cx, error) {
+        // sqlite3_result_error takes a string: passing an Error object
+        // directly would report an empty message
+        var message = error instanceof Error ? error.message : String(error);
+        sqlite3_result_error(cx, message, -1);
+    };
 
     /** Register a custom function with SQLite
       @example <caption>Register a simple function</caption>
@@ -1266,7 +1272,7 @@ Module["onRuntimeInitialized"] = function onRuntimeInitialized() {
             try {
                 result = func.apply(null, args);
             } catch (error) {
-                sqlite3_result_error(cx, error, -1);
+                setFunctionError(cx, error);
                 return;
             }
             setFunctionResult(cx, result);
@@ -1367,7 +1373,7 @@ Module["onRuntimeInitialized"] = function onRuntimeInitialized() {
                 state[p] = step.apply(null, mergedArgs);
             } catch (error) {
                 delete state[p];
-                sqlite3_result_error(cx, error, -1);
+                setFunctionError(cx, error);
             }
         }
 
@@ -1378,7 +1384,7 @@ Module["onRuntimeInitialized"] = function onRuntimeInitialized() {
                 result = finalize(state[p]);
             } catch (error) {
                 delete state[p];
-                sqlite3_result_error(cx, error, -1);
+                setFunctionError(cx, error);
                 return;
             }
             setFunctionResult(cx, result);

test/test_aggregate_functions.js

@@ -99,6 +99,25 @@ exports.test = function (SQL, assert) {
         3,
         "Aggregate functions work after an exception has been thrown in finalize"
     );
+
+    db.create_aggregate("throws_error_step", {
+        step: (state, value) => { throw new Error("step error object"); },
+    });
+    assert.throws(
+        () => db.exec("SELECT throws_error_step(column1) FROM (VALUES (1));"),
+        /step error object/,
+        "Reports the message of an Error thrown in a step function"
+    );
+
+    db.create_aggregate("throws_error_finalize", {
+        step: (state, value) => value,
+        finalize: (state) => { throw new Error("finalize error object"); },
+    });
+    assert.throws(
+        () => db.exec("SELECT throws_error_finalize(column1) FROM (VALUES (1));"),
+        /finalize error object/,
+        "Reports the message of an Error thrown in a finalize function"
+    );
 }
 
 // helper function to calculate a percentile from an array. Will modify the

test/test_functions.js

@@ -149,7 +149,11 @@ exports.test = function(SQL, assert){
 
   db.create_function("throwFunction", function () { throw "internal exception"; return 5;} );    
   assert.throws(function(){db.exec("SELECT throwFunction()");},/internal exception/, "Can handle internal exceptions");
-
+
+  db.create_function("throwErrorFunction", function () { throw new Error("internal error object"); });
+  assert.throws(function(){db.exec("SELECT throwErrorFunction()");},/internal error object/, "Reports the message of a thrown Error");
+  assert.equal(db.exec("SELECT addOne(1);")[0]["values"][0][0], 2, "Functions work after an Error has been thrown");
+
   db.create_function("customeObjectFunction", function () { return {test:123};} );    
   assert.throws(function(){db.exec("SELECT customeObjectFunction()");},/Wrong API use/, "Reports wrong API use");