JS: make CoerceError inherit Error, fixing console log

JavaScript is happy throwing any objects, but it doesn't neccessarily show it well in the console
(Only something like "Uncaught {...}").
When the class extends error, it has the correct toString conversion

Resolves #1831

src/Framework/Framework/Resources/Scripts/shared-classes.ts

@@ -4,13 +4,15 @@ export class DotvvmPostbackError {
     toString() { return "PostbackRejectionError(" + JSON.stringify(this.reason, null, "   ") + ")"}
 }
 
-export class CoerceError implements CoerceErrorType {
+export class CoerceError extends Error implements CoerceErrorType {
     isError: true = true
     wasCoerced: false = false
     get value(): never {
         throw this
     }
-    constructor(public message: string, public path: string = "") {
+    constructor(message: string, public path: string = "") {
+        super(message)
+        this.name = "CoerceError"
     }
     public static generic(value: any, type: TypeDefinition) {
         return new CoerceError(`Cannot coerce '${value}' to type '${type}'.`);

src/Framework/Framework/Resources/Scripts/tests/coercer.test.ts

@@ -1,5 +1,6 @@
-import { tryCoerce } from "../metadata/coercer"
+import { coerce, tryCoerce } from "../metadata/coercer"
 import { formatTypeName } from "../metadata/typeMap";
+import { CoerceError } from "../shared-classes";
 import { initDotvvm } from "./helper";
 
 initDotvvm({
@@ -619,3 +620,19 @@ test("formatTypeName", () => {
     expect(formatTypeName({ type: "nullable", inner: "t2" })).toBe("t2?");
     expect(formatTypeName([ { type:"nullable", inner: [ [ "t1" ] ] }])).toBe("MyType1[][]?[] (t1[][]?[])");
 })
+
+
+test("Exception - inherits Error", () => {
+    let hasError = false;
+    try {
+        coerce("something", "Int32")
+    } catch (e: any) {
+        hasError = true;
+        expect(e instanceof Error).toBeTruthy();
+        expect(e instanceof CoerceError).toBeTruthy();
+        expect(e.message).toBe("Cannot coerce 'something' to type 'Int32'.");
+        expect(e.name).toBe("CoerceError");
+        expect("" + e).toBe("CoerceError: Cannot coerce 'something' to type 'Int32'.");
+    }
+    expect(hasError).toBeTruthy();
+})