How to get 'Live Editor Evaluation Helper' .m file name from live script through another live script?

I am running two live scripts, let's call them main.mlx and sub.mlx. Below are minimal working examples.

The main.mlx:

dbstack().file

sub

The sub.mlx:

dbstack().file

When running dbstack().file in a live script, a file name "LiveEditorEvaluationHelper(randomNumbers).m" is returned. If sub.mlx is run manually, it returns a different Live Editor file name than when main.mlx is run (which it should). When sub.mlx is called through main.mlx though, the same Live Editor file name is returned twice, which is obviously incorrect.

I need to be able to get the "LiveEditorEvaluationHelper(randomNumbers).m" from sub through main. I have multiple subscripts, and the "LiveEditorEvaluationHelper(randomNumbers).m" changes everytime MATLAB is restarted, so running it once and then just saving the name as a variable is very impractical. Using

f = matlab.desktop.editor.getActiveFilename

also doesn't work, since the "active file" is main.mlx. I am assuming just calling sub.mlx through main.mlx doesn't activate the script, so it isn't added on the dbstack struct, but I can't seem to find a way around this. I have seemingly looked everywhere, and can't find an answer to this. I apologize in advance if the solution to this is glaringly obvious. Thanks for your help!

[Steven Lord]

What specifically are you hoping/trying to do with this information if you can get it?

[Mathias]

Hi @Steven Lord!

For educational purposes, I need to write my code in Live Scripts, where I have a script to simulate physical phenomena. This is divided up into subscripts based on parts of the simulation. I need to use the Live Script to be able to explain what several functions do and how they work. Some of these functions are in subscripts, but are also used in the main script. Just executing the subscript in the main.mlx like

sub

doesn't allow for subscript functions to be saved in the workspace, and thus can't be called in the main script. A work-around for this is creating myFunction.m in the same folder instead, so I can call the function in main.mlx that way. However, that only statically works when myFunction.m doesn't change. That's not the case: I want to be able to alter the function code in sub.mlx (where explanations, LaTeX equations and figures are present), and then dynamically update myFunction.m in the background, so that main.mlx can now call the updated function "seemingly" from sub.mlx. The algorithm I wrote to do this works perfectly if I manually run sub.mlx. However, if I then execute sub.mlx through main.mlx, the function doesn't work anymore. Find the code below. I have a strong feeling as to why this fails.

function saveFunction(functionName)
    stack = dbstack;            % Get the current script filename and line number
    scriptName = stack(2).file; % The file where the function is called
    
    % Open the script file
    fid = fopen(scriptName, 'r');
    if fid == -1
        error('Cannot open the file: %s', scriptName);
    end
    
    % Initialize variables to track lines
    currentLine = stack(2).line; % The line where the function is called
    linesToSave = {};
    foundFunction = false;
    
    % Read the file and move upwards, starting just above the current line
    lineNumber = currentLine - 1;
    while lineNumber > 0
        % Read the current line
        lineNum = 1;
        fseek(fid, 0, 'bof'); % Reset fgetl
        while lineNum < lineNumber
            fgetl(fid); % Skip the lines until the target line
            lineNum = lineNum + 1;
        end
        tline = fgetl(fid);
        
        % Check if we found a 'function' keyword in this line
        if contains(tline, 'function')
            foundFunction = true;
            linesToSave{end+1} = tline; % Save the line with 'function'
            break; % Stop since the full function definition has been found
        end
        
        % Add the line to the linesToSave list
        linesToSave{end+1} = tline;
        
        % Decrease the line number to move upwards
        lineNumber = lineNumber - 1;
    end
    
    % Close the file
    fclose(fid);
    
    % If no function was found, raise an error
    if ~foundFunction
        error('No function definition found in the script before the call.');
    end
    
    % Save the collected lines to a text file with the functionName
    fileID = fopen(['Functions/', functionName, '.m'], 'w');
    if fileID == -1
        error('Cannot create the file: %s.m', functionName);
    end
    
    % Write the lines to the text file
    for i = length(linesToSave):-1:1
        fprintf(fileID, '%s\n', linesToSave{i});
    end
    
    % Close the output file
    fclose(fileID);
    
    disp(['Code saved successfully as Functions/', functionName, '.m']);
end

Provided a folder "Functions" already exist in the current folder and is added to the path, the function is called like

% a function in sub.mlx
function a = myFunction(b, c)
    a = b + c;
end
saveFunction('myFunction');

where it looks for the closest function above where it was called, and saves it accordingly. (Yes, I know this won't work with nested functions, that's fine.) As I said, this works beautifully when running sub.mlx. When executed through main.mlx though, the active file is main.mlx, not sub.mlx, and sub.mlx (and the actual .m file running in the background, "Live Editor Helper ...") is not added to dbstack. So, stack, scriptName and currentLine fail to deliver what they should. I have tried to alter this algorithm to make it work, but can't seem to fix it. Any help is welcome!

Answer 1

[Walter Roberson]

When sub.mlx is called through main.mlx though, the same Live Editor file name is returned twice, which is obviously incorrect.

No, what you are seeing is the automatic output of ans because you do not have a semi-colon on the call to sub

file q2174453.mlx

dbstack().file
sub

file sub.mlx

dbstack().file

Output is

ans = 'LiveEditorEvaluationHelperEeditor78579DB3_B29EA684.m'

ans = 'sub.mlx'

ans = 'LiveEditorEvaluationHelperEeditor78579DB3_B29EA684.m'

I admit to being a bit unclear as to why ans at the end is not sub.mlx since sub.mlx is being executed as-if it were a script

Anyhow, to get at the LiveEditorEvaluationHelper(randomNumbers).m file name, use dbstack(1).file

[Mathias]

Hi Walter,

Thanks for your answer! I used dbstack(2).file before, and this doesn't work either, or maybe I'm doing it wrong. When using dbstack(2).file (I've tried it with and without semi-colon, both in sub and in main, both with and without disp()), I either get nothing as an output, or an error. I am really having the feeling that running a live script by writing its name in another live script, isn't interpreted as a function call and thus doesn't add it to the dbstack. Could you kindly show me a working example where running main.mlx can return both its own LiveEditorEvaluationHelper(randomNumbers).m and the one from sub.mlx? Many thanks!

[Walter Roberson]

It turns out that the numeric parameter to dbstack is the number of frames to omit, so to get at the second frame only you need to assign the output of dbstack to a variable and then index the variable. (In the case where you know for sure that there are exactly two levels you can dbstack(1).file directly)

[Walter Roberson]

file q2174453.mlx

'main is here'
dbstack().file
sub

file sub.mlx

'sub is here'
foo = dbstack;
foo(2).file
dbstack(1).file

Output is

ans = 'main is here'

ans = 'LiveEditorEvaluationHelperEeditor85515B63_925A5E4C.m'

ans = 'sub is here'

ans = 'LiveEditorEvaluationHelperEeditor85515B63_925A5E4C.m'

ans = 'LiveEditorEvaluationHelperEeditor85515B63_925A5E4C.m'

[Mathias]

Hi @Walter Roberson,

The answer you've provided still uses dbstack, and still produces the same "LiveEditorEvaluationHelperEeditor....m" when running main.mlx for both sub.mlx and main.mlx, while sub.mlx should return a different .m file. You can prove this by just running the command

dbstack().file

in both Live Scripts manually, they will return different answers. I need to get the sub.mlx Live Editor Helper .m file name through running main.mlx. I'm not sure as to how two interacting files would work in the online version of MATLAB, but running R2024b on my desktop, this still returns the Live Editor Helper .m file name of main.mlx every time. When analysing what's present in dbstack, just running

sub

is apparently not considered a function call, so it's not added to dbstack. Is there another way of getting this Live Editor Helper .m file name of a .mlx script through another .mlx script? I've tried wrapping it in

run('sub.mlx'); % With and without semi-colon

but that doesn't work either (although the run.m function is now added to dbstack when analysed).

[Walter Roberson]

In the case where a mlx is called from inside a mlx, as-if a function or script call, then it is not clear that LiveEditorEvaluationHelperEeditor....m is used. dbstack reflects the .mlx name in this case, whereas it reflects LiveEditorEvaluationHelperEeditor....m name for the outer mlx, so it might be that somehow the mlx is considered to be running directly.