Not able to save toolbox folders to pathdef.m in MATLAB 2025b

Hi,

I am running issues with the addon/toolbox path behaviour in MATLAB 2025b. My only other reference is MATLAB 2022b in which it works fine.

I have 2 toolboxes installed that I care about:

Name                        Version     Enabled                  Identifier              
_________________________________________    _________    _______    ______________________________________                 
"GUI Layout Toolbox"                         "2.3.5"       true      "e5af5a78-4a80-11e4-9553-005056977bd0"
"Widgets Toolbox"                            "1.3.330"     true      "b0bebf59-856a-4068-9d9c-0ed8968ac9e6"

When I launch MATLAB it's all ok and I see the folders needed in path:

C:\Users\username\AppData\Roaming\MathWorks\MATLAB Add-Ons\Toolboxes\Widgets Toolbox
C:\Users\username\AppData\Roaming\MathWorks\MATLAB Add-Ons\Toolboxes\Widgets Toolbox\demo
C:\Users\username\AppData\Roaming\MathWorks\MATLAB Add-Ons\Toolboxes\Widgets Toolbox\doc
C:\Users\username\AppData\Roaming\MathWorks\MATLAB Add-Ons\Toolboxes\Widgets Toolbox\doc\helpsearch-v3
C:\Users\username\AppData\Roaming\MathWorks\MATLAB Add-Ons\Toolboxes\Widgets Toolbox\resource
C:\Users\username\AppData\Roaming\MathWorks\MATLAB Add-Ons\Toolboxes\Widgets Toolbox\widgets
C:\Users\username\AppData\Roaming\MathWorks\MATLAB Add-Ons\Toolboxes\GUI Layout Toolbox\layout
C:\Users\username\AppData\Roaming\MathWorks\MATLAB Add-Ons\Toolboxes\GUI Layout Toolbox\layoutdoc

However, I when I use path(pathdef) to reset paths (which used to reset to the same state as at launch in my case), the folders for these toolboxes disappear.

I can see that they are not defined in pathdef.m, and if I call savepath after launching MATLAB, these folders will not get saved even if they are on the path, because for some reason they are in the ExcludePathStore list:

>> matlab.internal.path.ExcludedPathStore.getCurrentExcludeList()'

ans = 

8×1 string array

"C:\Users\username\AppData\Roaming\MathWorks\MATLAB Add-Ons\Toolboxes\Widgets Toolbox"
"C:\Users\username\AppData\Roaming\MathWorks\MATLAB Add-Ons\Toolboxes\Widgets Toolbox\demo"
"C:\Users\username\AppData\Roaming\MathWorks\MATLAB Add-Ons\Toolboxes\Widgets Toolbox\doc"
"C:\Users\username\AppData\Roaming\MathWorks\MATLAB Add-Ons\Toolboxes\Widgets Toolbox\doc\helpsearch-v3"
"C:\Users\username\AppData\Roaming\MathWorks\MATLAB Add-Ons\Toolboxes\Widgets Toolbox\resource"
"C:\Users\username\AppData\Roaming\MathWorks\MATLAB Add-Ons\Toolboxes\Widgets Toolbox\widgets"
"C:\Users\username\AppData\Roaming\MathWorks\MATLAB Add-Ons\Toolboxes\GUI Layout Toolbox\layout"
"C:\Users\username\AppData\Roaming\MathWorks\MATLAB Add-Ons\Toolboxes\GUI Layout Toolbox\layoutdoc"

so my question is - is there a way to replace path(pathdef) with something that includes the toolbox folders as on MATLAB startup? I can find the install paths of the addons but with genpath it would end up including more folders than needed.

I could use matlab.internal.path.ExcludedPathStore.getCurrentExcludeList() to add them but not sure if that's the best approach as it's an internal class with no documentation that I could find.

[Steven Lord]

However, I when I use path(pathdef) to reset paths (which used to reset to the same state as at launch in my case), the folders for these toolboxes disappear.

What is your use case for doing this? path(pathdef) is a pretty heavy hammer. Depending on what exactly you're doing, there may be a less expensive way to achieve your goal.

[Titas Bucelis]

So in my case it's because if I want to change to working on a different project. Some of them have same function defined but sometimes with some differences to fit the project better. So I want to reset what was added to path when switching tools to make sure correct versions of functions get called and the result does not depend on the order I use various tools. This worked fine in the previous MATLAB releases so just looking for a way to achieve previous behaviour

[dpb]

This is new behavior since the latest release I've installed and I fail to understand what would be behind the exclusion and it is undocumented (and afaict not ever mentioned as existing in the documentation) so I went poking to see if could learn anything about it...

f=which('matlab.internal.path.ExcludedPathStore')

f = '/MATLAB/toolbox/matlab/general/+matlab/+internal/+path/ExcludedPathStore.m'

type(f)

classdef ExcludedPathStore < handle
    %

    % Copyright 2020-2023 The MathWorks, Inc.

    properties (Access = private)
        ExcludedPathEntries = string.empty;
    end

    methods (Static, Hidden, Access = private)
        function obj = getInstance()
            mlock;
            persistent instance
            if isempty(instance)
                instance = matlab.internal.path.ExcludedPathStore();
            end
            obj = instance;
        end
    end

    methods (Static, Hidden)
        % Adds the folder pathToExclude to the list of folders that savepath filters
        % from the path before generating pathdef.m.
        function addToCurrentExcludeList(pathToExclude)
            arguments (Input)
                pathToExclude (1,1) string
            end

            currentInstance = matlab.internal.path.ExcludedPathStore.getInstance();
            addToExcludeList(currentInstance, pathToExclude);
        end

        % Undoes the effect of addToCurrentExcludeList, given the same input argument.
        function removeFromCurrentExcludeList(pathToRestore)
            arguments (Input)
                pathToRestore (1,1) string
            end

            currentInstance = matlab.internal.path.ExcludedPathStore.getInstance();
            removeFromExcludeList(currentInstance, pathToRestore);
        end

        % Returns a string array containing the current list of excluded folders, each
        % of which is in canonicalized form. Exclude-list elements that cannot be
        % canonicalized are not included in the output.
        function excludeList = getCurrentExcludeList()
            arguments (Output)
                excludeList (1,:) string
            end

            currentInstance = matlab.internal.path.ExcludedPathStore.getInstance();
            excludeList = getExcludeList(currentInstance);
        end
    end

    methods (Access = private)
        function obj = ExcludedPathStore()
        end

        function excludeList = getExcludeList(obj)
            excludeList = rmmissing(arrayfun(@(pth) builtin("_canonicalizepath", pth), ...
                                             obj.ExcludedPathEntries, ...
                                             ErrorHandler = @(~, ~) string(missing)));
        end

        function addToExcludeList(obj, aPath)
            obj.ExcludedPathEntries(end+1) = aPath;
        end

        function removeFromExcludeList(obj, aPath)
            obj.ExcludedPathEntries(find(obj.ExcludedPathEntries == aPath, 1)) = [];
        end
    end
end

The internal comments are pretty-much just saying the functions do what they say they do by name but there's no explanation of why this is being done nor who is in charge of deciding who is/is not on the do not fly list.(a lot like TSA, it appears).

Hopefully @Steven Lord will come back and comment further since he did ask about the use, but as I understand your purpose, it would seem your option would basically be the one you proposed or take a chance and purge the list and see what bad may happen, if anything (you could always repopulate it if that were to actually break something).

There must have been some logic behind introducing this, but it certainly isn't obvious to me what it would be. I presume there must be some registry of add-ons; maybe classes of them such that a pedigree or provenance is needed to make the permanent list?

OBTW, the word "pathdef" didn't make any release note according to the search tool which did seem to find all instances of "path", none of which appeared to have anything at all to do with this peculiarity.

[Steven Lord]

I was having a little trouble responding to this post on my machine yesterday, but the problem seems to have subsided.

Rather than manually trying to control the path yourself, if you're working on projects that include lots of files where each project needs a different subset of directories to be on the path I'd consider using the Projects functionality included in MATLAB. This will handle adding directories to the path when you start working on a project and restoring the path to its previous state (note this is different than either "removing directories from the path" or "restoring the path to its default") when you stop working on that project and/or switch to working on a different project.

[dpb]

So, can you expound some on the "why" behind this, Steven, and what determines which TB files will/will not be on the list and why?

Answer 1

[Titas Bucelis]

So looks like matlab.internal.path.ExcludedPathStore gets populated when addon is enabled (which I assume happens at startup), so I figured 3 ways to re-add addon paths:

1. For my use case I am going to go with this at the moment: use matlab.internal.path.ExcludedPathStore.getCurrentExcludeList() which I haven't seen used anywhere else yet so hoping that addon paths are the only use

if ~isMATLABReleaseOlderThan("R2025b")
    % Not sure what the oldest version needing this is, but in 2022b this
    % is not needed and will break (no getCurrentExcludeList() method)
    addpath(strjoin(matlab.internal.path.ExcludedPathStore.getCurrentExcludeList(), ';'), '-end');
end

• Re-enable each addon using for example `matlab.addons.enableAddon('Widgets Toolbox')

addons = matlab.internal.addons.getAddonInstallations();
for addon = addons
    matlab.addons.enableAddon(addon.Name);
end

• Get paths of each addon from the addons cache, but I found this to be really slow when you first call it after MATLAB restart (7s)

installedAddonsCache = com.mathworks.addons_common.notificationframework.InstalledAddOnsCache.getInstance;
addons = matlab.internal.addons.getAddonInstallations();
if ~isempty(addons)
    addons = addons([addons.Enabled]);
    for identifier = [addons.Identifier]
        installedAddon = installedAddonsCache.retrieveAddOnWithIdentifier(identifier);
        addon_paths = string(installedAddon.getCustomMetadataWithAttributeName('matlabPathEntries').getValue());
        addpath(strjoin(addon_paths, ';'),'-end')
    end
end

[dpb]

if ~isMATLABReleaseOlderThan("R2025b")
    % Not sure what the oldest version needing this is, but in 2022b this
    % is not needed and will break (no getCurrentExcludeList() method)

What about

if ~(exist('matlab.internal.path.ExcludedPathStore','class')==5)
  ... 

to see if the classdef exists or not to remove the uncertainty about the actual specific release?

[Titas Bucelis]

@dpb good suggestion! Although I have no idea if the behaviour for how addon paths are handled has changed at the same time. It's probably a good assumption as for example 2022b uses matlab.internal.language.ExcludedPathStore instead

[dpb]

Well, that doesn't help, it turns out because on R2022b exist can't find the hidden/private file as it does on R2025. Nor can which so one would have to do an exhaustive file search to locate it.

I never have built anything large enough that seemed to justify a project; it appears to have been introduced in R2019a but R2019b doesn't incorporate it yet, so still not at all clear as to why it was introduced. As you note, it appeared by R2021b in the +language folder as well as R2022b, the latest version I've installed so far.