Add an error message in the problems panel for when the condition is false.

libs/base/control.ts

@@ -55,6 +55,7 @@ namespace control {
 
         UNHANDLED_EXCEPTION = 999,
     }
+
     /**
      * Display an error code and stop the program.
      * @param code an error number to display. eg: 5
@@ -64,15 +65,28 @@ namespace control {
     //% shim=pxtrt::panic
     export function panic(code: number) { }
 
+    //% shim=U::userError
+    function _throwValue(msg: string) { }
+
     /**
-     * Display an error code and stop the program when the assertion is `false`.
+     * Display an error message, an error code, and stop the program when the assertion is `false`.
+      @code (optional) an error number to display. eg: 5
      */
     //% help=control/assert weight=30
     //% blockId="control_assert" block="assert %cond|with value %code"
-    export function assert(cond: boolean, code: number) {
-        if (!cond) {
-            fail("Assertion failed, code=" + code)
-        }
+    export function assert(cond: boolean, code?: number) {
+         if (!cond) {
+         // adapted this idea from how real browsers work and optionally kept the code parameter for clearer diagnostics
+         // added the message also because the original one for receiving the message is only logged
+         // in the console, not together in the panel
+         const msg = code !== undefined
+            ? `Assertion failed, code: ${code}`
+            : `Assertion failed`
+
+         console.log(msg)
+         dmesg(msg)
+         _throwValue(msg)
+         }
     }
 
     export function fail(message: string) {
@@ -158,14 +172,12 @@ namespace control {
     export declare function programName(): string;
 
     //% shim=control::_ramSize
-    function _ramSize() {
-        return 32 * 1024 * 1024;
-    }
-
+   declare function _ramSize(): number;
+
     /** Returns estimated size of memory in bytes. */
     export function ramSize() {
         return getConfigValue(DAL.CFG_RAM_BYTES, 0) || _ramSize();
-    }
+     }
 
     /** Runs the function and returns run time in microseconds. */
     export function benchmark(f: () => void) {

libs/base/docs/reference/control/assert.md

@@ -1,6 +1,6 @@
 # assert
 
-Display an error number and stop the program if the assertion condition is false.
+Display an error message, error number, and stop the program if the assertion condition is false.
 
 ```sig
 control.assert(false, 0)
@@ -11,9 +11,9 @@ You can insist that your program will stop at an assert block if a certain condi
 ## Parameters
 
 * **cond**: a [boolean](/types/boolean) where true means everything is ok or false which means, stop the program!
-* **code**: an error [number](/types/number) you match to an error situation in your program.
+* **code**: an optional parameter for displaying an error [number](/types/number) you match to an error situation in your program.
 
-## Example #example
+## Example 
 
 Stop the program if a sensor connected to pin `A0` sends a low (`0`) signal.
 
@@ -24,10 +24,10 @@ forever(function () {
 })
 ```
 
-## See also #seealso
+## See also
 
 [panic](/reference/control/panic)
 
 ```package
 base
-```
+```