Debugger does not show named return variable

[ernestasjuska]

Hello,

AL language debugger does not show named return variable Value that is [equivalent to] a local variable:

Using regular local variable works (obviously):

Although, the actual return value should be shown too in case it would be returned from a helper method, e.g. exit(MyMethod());.

Thanks.

BC platform version: 26.0.33990.0
BC application version: 26.1.33404.34029
AL Language version: 15.0.1433841
BC extension runtime version: 15.0
VS Code version: 1.101.2

Internal work item: AB#582313

[svallmen]

In fact, the debugger does not show any local variables anymore, when it reached the end; of the procedure. Only parameters are still there.
This also includes the Return pseudo variable that used to hold the value from the exit statement in a function with an unnamed return value.

[svallmen]

I noted that sometimes, even within the body of a procedure, local variables are missing from the VARIABLES - Local section. Is there some code optimization in place that optimizes them away?

[ernestasjuska]

Generated C# code still has those variables and debugger can see them even if they are not used. This is a problem with debugger not recognizing all available variables. Even if variables would be removed in optimization process, their names are still specified in the method attributes that are not removed since they can be used at runtime.

For example, this AL code

gets converted to this C# code

// ...
        [SignatureSpan(5629585434869784L)]
        [SourceSpans(7036904484175880L)]
        [NavName("Test")]
        [MethodId(1096493258)]
        [ReturnValue("ReturnVar")]
        [LocalsNames("LocalVar")]
        [MethodScopeFlags(MethodScopeFlags.IsStackFrame)]
        private async ValueTask<NavText> Test()
        {
            ALMethodScope<(NavText localVar, NavText returnVar)> \u03b3scope = default;
            try
            {
                \u03b3scope = new ALMethodScope<(NavText localVar, NavText returnVar)>(this, "Test", MethodScopeFlags.None, 1096493258);
                \u03b3scope.ALStart();
                \u03b3scope.Target.localVar = NavText.Default(0);
                \u03b3scope.Target.returnVar = NavText.Default(0);
                {
                }

                return \u03b3scope.Target.returnVar;
            }
            catch (Exception \u03b1e)when (\u03b3scope?.ALException(\u03b1e, out NavALException \u03b1ale) == true)
            {
                throw \u03b1ale;
            }
            finally
            {
                if (\u03b3scope != default)
                {
                    \u03b3scope.ALFinally();
                    \u03b3scope.Dispose();
                }
            }
        }
// ...

Even if you don't use named return variable, C# code has one

// ...
        [SignatureSpan(5629585434869784L)]
        [SourceSpans(6755429507399688L)]
        [NavName("Test")]
        [MethodId(1096493258)]
        [ReturnValue]
        [LocalsNames("LocalVar")]
        [MethodScopeFlags(MethodScopeFlags.IsStackFrame)]
        private async ValueTask<NavText> Test()
        {
            ALMethodScope<(NavText localVar, NavText \u03b3retVal)> \u03b3scope = default;
            try
            {
                \u03b3scope = new ALMethodScope<(NavText localVar, NavText \u03b3retVal)>(this, "Test", MethodScopeFlags.None, 1096493258);
                \u03b3scope.ALStart();
                \u03b3scope.Target.localVar = NavText.Default(0);
                \u03b3scope.Target.\u03b3retVal = NavText.Default(0);
                {
                }

                return \u03b3scope.Target.\u03b3retVal;
            }
            catch (Exception \u03b1e)when (\u03b3scope?.ALException(\u03b1e, out NavALException \u03b1ale) == true)
            {
                throw \u03b1ale;
            }
            finally
            {
                if (\u03b3scope != default)
                {
                    \u03b3scope.ALFinally();
                    \u03b3scope.Dispose();
                }
            }
        }
// ...

So, it don't see a technical reason why return variable cannot be shown in the debugger local variables section.

[NonDebuggable] procedures and variables should be hidden. However, it would be nice to see placeholder lines in debugger callstack that shows that something is happening, e.g:

<non-debuggable procedure> from App ABC
<non-debuggable procedure> from App ABC
<non-debuggable procedure> from App ABC
DebuggableProcedure2
DebuggableProcedure1
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