Comments on: User-defined tab completions – take 2

By: Yair Altman

Yair Altman — Wed, 28 Jan 2026 18:23:33 +0000

In reply to matlabtest. The description string can be provided using the "purpose" key/attribute, as explained here: https://www.mathworks.com/help/matlab/matlab_prog/customize-code-suggestions-and-completions.html For example: {"name":"in1", "kind":"required", "type":["numeric"], "purpose":"ID of item"}

By: matlabtest

matlabtest — Mon, 26 Jan 2026 17:46:56 +0000

In the picture below, the functions have a description on the right-side. Is this a part of the json as well? I looked at the built-in matlab function’s json, but could not find this description string anywhere. I’d like to provide the same for my custom built-in functions

https://www.mathworks.com/help/matlab/25a_command_window_suggestions.png

By: Yair Altman

Yair Altman — Sun, 18 Jan 2026 08:52:58 +0000

In reply to matlabtest.

As far as I can tell, basePath (or similar property) is not supported, only name, kind, type, purpose, repeating, tuple, platform and the quite-confusing mutuallyExclusiveGroup.
Perhaps there are some other undocumented properties, but I am not aware of any.

The syntax is now documented in Matlab:
https://www.mathworks.com/help/matlab/matlab_prog/customize-code-suggestions-and-completions.html

By: matlabtest

matlabtest — Fri, 16 Jan 2026 21:40:40 +0000

Hi,

can folders / paths be specified in functionSignatures.json, for example to default to another path?

“LoadInputFile”: {
“_description”: “Load a text input file”,
“inputs”: [
{
“name”: “filename”,
“kind”: “optional”,
“type”: “filepath=Folder2/Folder3/*.txt”,
“basePath”: “C://Folder1/Folder2/Folder3/”,
“purpose”: “some file is now loaded”
}
]
},

By: Yair Altman

Yair Altman — Thu, 01 Jun 2023 16:44:58 +0000

In reply to Arye. I am not familiar with a universal catch-all tab-completion mechanism for all functions, and it also doesn't make much sense to me, because different functions use different input arguments. If you have a finite number of functions, you can place them in a custom functionSignature file.

By: Arye

Arye — Wed, 31 May 2023 22:29:18 +0000

hi,
is there a universal functionSignature.json file that will allow my to get the function hints when opening brackets of my funcs?
something that automaticly recognize my function input reqrueid types

thanks,
Arye

By: matse

matse — Mon, 27 Jul 2020 15:06:20 +0000

Thanks for the post - I love your blog! It seems that - at least in 2020a - it is also possible to have the functionSignatures.json in a subfolder named resources. Matlab is using such a subfolder for example for the functions in toolbox/matlab/codetools.

By: Yair Altman

Yair Altman — Mon, 18 Feb 2019 20:44:00 +0000

In reply to Jim Van Zandt.

@Jim – you can implement a simple GUI that has an editbox, which searches for and displays the relevant file/folder completions whenever the user types anything in the editbox, as explained here: http://undocumentedmatlab.com/blog/editbox-data-input-validation

By: Jim Van Zandt

Jim Van Zandt — Mon, 18 Feb 2019 19:46:08 +0000

I have a significantly different use case (but one using many of the same keywords 🙂 – I have a function that asks the user to type in a path or file name, and I would like the function to tab-complete as the user types. The path might be anywhere in the directory tree, so adding JSON files everywhere is not practical. Do you know of a convenient way to implement that, using this function, or the GNU readline library, or something else?

By: Viktor Horvath

Viktor Horvath — Thu, 16 Nov 2017 18:52:25 +0000

In reply to Greg. Your comment was very helpful, thank you! I would like to add to it, because to me it was not obvious that in the case of Class methods the first argument must be declared in the functionSignatures.json with the proper type otherwise it will not work. For example:

classdef foo
    methods
        function out = bar(obj, arg)
            out = arg;
        end
    end
end

In order to have tab completion for the bar() method the corresponding functionSignatures.json file must contain the following.

{
    "foo.bar":
    {
        "inputs":
        [
            {"name":"obj","kind":"required","type":"foo"},
            {"name":"arg","kind":"required","type":"choices={'choice1','choice2'}"}
        ]
    }
}

Note the first entry in the input list is the object itself which can be used to generate options on the fly as shown in the article.