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Show HN: Infat – Declaritive application assocation manager for macOS

94 points - 04/24/2025


Bello! Made this to help navigate the tumultuous process of navigating to a new machine on Mac when you have a number of custom utilities setup for editing particular files. This is designed to make that as easy as possible, and add some magic on top of that, like setting mailto handlers or anything else of that breed. Use XDG_CONFIG_HOME to keep it organized.

Credit to https://github.com/moretension/duti for the original inspiration for the project.

Happy to answer and help with whatever.

Source
  • mlenz

    04/24/2025

    Great to see this, thanks for sharing! Do you have plans to make it available in nixpkgs and potentially as a home-manager or nix-darwin module? Then I could add it to my config and have everything set up automatically.

      • philocalyst

        04/24/2025

        I don't use nixpkgs personally but would love to give it a shot, check the repo in a day or two to give me some time to learn to ropes! I'll shoot you an email if I need any help :)

        • SOLAR_FIELDS

          04/25/2025

          The first question that came to mind for me is “is this already achievable with Nix-Darwin”? If not, it fits very well into the nix ecosystem

      • goranmoomin

        04/25/2025

        This is a bit tangent, but does anyone know how to block an app from ever deciding to become a file handler on macOS?

        Every time I install Chrome on my machine (for testing purposes), macOS decides that Chrome is going to be the default file handler for a bunch of file associations, including HTML, WebP, and so on… and I have to figure out which was which for all of the mappings (which is super frustrating).

        I can read Info.plist from the bundle of the specific app (in this case, Google Chrome) that declares all of the UTIs, and then figure out which file associations that Chrome has messed up, but I don’t know how to get the default file associations (if it was not Chrome) before it.

          • AdieuToLogic

            04/25/2025

            > This is a bit tangent, but does anyone know how to block an app from ever deciding to become a file handler on macOS?

            The information below does not "block an app" from taking over file handler associations. It may be beneficial on its own and/or provide a starting point for further exploration.

            > Every time I install Chrome on my machine (for testing purposes), macOS decides that Chrome is going to be the default file handler for a bunch of file associations, including HTML, WebP, and so on… and I have to figure out which was which for all of the mappings (which is super frustrating).

            The following command can display current file extension associations for a user account:

              plutil -convert xml1 \
                ~/Library/Preferences/com.apple.LaunchServices.plist \
                -o -
            
            In the XML output of the above should be the associations. As for determining changes, if Time Machine has been enabled, then changes to this plist can be identified.

            Also regarding a Chrome OS-X/macOS installation - it installs plists for unconditional background updates. This may not be a desirable feature.

              • emmelaich

                04/25/2025

                    ~/Library/Preferences/com.apple.LaunchServices/com.apple.LaunchServices.plist
                
                ... but that didn't seem to be the right file either? Sequioa 15.4 here.

            • philocalyst

              04/25/2025

              MacOS doesn't give any way to block an association from happening, I'm assuming they're using the same API's under the hood that Duti is using, and the only way you could block that from being accessed is by disabling the Launch services API.

              In the next release of Infat, I'm introducing listing the openers from the plist (As you're doing now). If you record these values, then get their set defaults through infat, you could put those into your config and load from you config whenever they're overriden!

              Best I got... Shameless promotion

          • badmonster

            04/25/2025

            Would you consider adding support for domain-specific overrides (e.g., open *.notion.site links with Chrome but other URLs with Safari) in future versions?

              • beaugunderson

                04/25/2025

                I use Hammerspoon for this and it's super configurable via Lua--open some URLs with Chrome profile 1, some with profile 2, some in incognito, open normal Spotify links with the Spotify app, normal Zoom links with Zoom (skip opening a tab that then opens the zoom:// link), etc.

                For Google Drive links I open a picker that lets me choose from two chrome profiles and incognito.

                  • 037

                    04/25/2025

                    Would you mind sharing some tips on how to set that up? A code snippet or a link to the relevant docs would be super helpful.

                  • badmonster

                    04/25/2025

                    cool

                • philocalyst

                  04/25/2025

                  Thank you for the question! I didn’t even think of this use case. I’ll setup regex (and wildcards) but not scripting.

                  Check back in a week!

            • 037

              04/25/2025

              I love that it’s a command line tool — I’ll try it soon.

              I use OpenIn for this [1] (it’s paid, but a one-time purchase at a very reasonable price). It works with URLs too, supports “browser profiles”, and lets you create logic using JavaScript (e.g., do X if the filename contains Y, or do Z if a modifier key is pressed).

              It works really well and even has the ability to “fix” what external apps have changed. I plan to use this on new Macs to reconstruct my app associations and rules.

              I do wish the rules were defined in plain text files — sometimes it’s hard to follow the logic through the UI and the way it handles things.

              Another comment mentions Hammerspoon (which I used in the past — it was very nice). Maybe I can rebuild part of my current setup with it.

              [1] https://loshadki.app/openin4/

                • philocalyst

                  04/25/2025

                  I loveee hammerspoon. And had a subscription to OpenIn a bit back. Advanced scripting isn’t going to happen, even paging out to another script. Recently committed to Regex which would cover most of that. I’ll look into how it “fixes” old associations.

                    • philocalyst

                      04/25/2025

                      Walking back my regex commitment, just a heads-up/apology if you had your hopes up. Want this to stay as a CLI and not a dynamic app. Let me know if there's anything else you could see useful that would fit within that scope!

              • KolenCh

                04/25/2025

                I see that you mentioned it is inspired by duti. I think may be adding a comparison on how it solves what it couldn’t would be beneficial.

                From quick skim and memory it seems a notable one is url scheme association.

                One problem I had with duti is to associate extensions automatically from a pre defined “table”. Automating that involves shell scripting[^1]. Also associating extension to softwares that hasn’t been installed. Another pain point is there’s two ways to associate and depending on different cases one is better than another.

                [1]: https://github.com/ickc/bootstrapping-os-environments/blob/m...

                • igor47

                  04/25/2025

                  Does anyone know of a similar tool to manage associations on Linux? I'm tired of having random files opening with random tools whenever I install them. Recently, csv files began opening with krita for instance...

                  • deeThrow94

                    04/24/2025

                    Oh this is very exciting! I do have a request, though—I want to list all file extensions an application can open, specifically so I can use this to ensure xcode isn't the default for anything but xcode-specific files.

                      • philocalyst

                        04/24/2025

                        Have an idea of how I would do this already, give me until the end of the week. To be clear, an interface like this?

                        Infat list [--identifier] [--application] Where identifier and application are mutually exclusive, and application lists the openers it is capable of opening by default? Merging the application flag for simplicities sake, so either returns a list with both their possibilities *and* the assigned apps.

                        Thoughts?

                          • deeThrow94

                            04/24/2025

                            Love it! Seems like it'd be easy to filter out extensions I wanna keep and switch them all to emacs or whatever.

                    • dmwood

                      04/24/2025

                      Shell dependencies for install? Got: bash-3.2# just package && mv dist/infat* /usr/local/bin/infat # Wildcard because output name includes platform bash: just: command not found

                        • philocalyst

                          04/24/2025

                          No dependencies for install, just is the command runner I use to keep things organized, it's a replacement for make(1). If it hurts to download just, you can build using SPM:

                          swift build -c release

                          mv .build/PLATFORM/release/infat /usr/local/bin

                          • alkh

                            04/24/2025

                            just is a great command runner[1], not a shell script. Looks like it is needed if you build from source or install from Github releases. Alternatively, use `brew install philocalyst/tap/infat`(haven't done it myself but I bet it has just as a dependency anyway) [1] https://github.com/casey/just

                        • FabHK

                          04/25/2025

                          Typo: Declarative (think of declaration, not declarition)

                            • philocalyst

                              04/25/2025

                              THANK YOU! i knew something was wrong. i knew i knew i was missing it ;)

                          • stinger

                            04/24/2025

                            Running into this error - "Error: Failed to set default application: The file couldn’t be opened." This seems to be happening for extensions that I haven't opened yet (md, json, mailto, etc.) For a new laptop, this might not be available yet. Once I `touch` a file with those extensions, the config works!. FYI, I am using a config.toml file btw.

                              • philocalyst

                                04/24/2025

                                Okay, confusing -- just tried to replicate on my machine and couldn't get that error. When you say touch, you mean creating a file with that extension, or any interaction period?

                                Could you please try to replicate with verbosity enabled (-v) and email me the output or file an issue at the repo with the results and full summary? It's helpful for tracking. Sorry this isn't a quick fix :(

                                  • stinger

                                    04/28/2025

                                    Thanks. Looks like the update fixed it.

                            • hk1337

                              04/25/2025

                              Is there a way to pass arguments or some other options? For example, TextEdit can be opened in plain text or rich text mode.

                                • philocalyst

                                  04/25/2025

                                  There is not, infat is subject to the limitations of Apple's API for setting handlers, which do not support passing in any data that an application could work with. If you wanted to, and have the time, I would recommend setting up a wrapper with https://github.com/sveinbjornt/Platypus with applescript. Then you could make an alternate for whichever mode you please and set it as an opener using infat. Clunky but functional.

                              • alkh

                                04/24/2025

                                That's great, I've struggled with this problem a lot. To double-check, this essentially allows you to specify a default app that is being opened when you click on a file via Finder or via terminal's `open` program, correct? I haven't seen this exact clarification in README

                              • timenova

                                04/24/2025

                                This is amazing! I set a few extensions manually.

                                However, does anyone know a way to set all text-like documents to open with a single editor (for example Zed) on Mac? Even text files without any extensions?

                                  • philocalyst

                                    04/24/2025

                                    It wouldn't be possible with the current interface, but I have a feeling it's possible. I'm thinking it's part of a new configuration option "type" that allows you to define openers for categories of files (text,video,etc.)

                                    I can get it out in a week ;)

                                      • timenova

                                        04/24/2025

                                        That would be amazing honestly!

                                • millzlane

                                  04/25/2025

                                  This is pretty sweet! Could this set tel: to open in teams?

                                  • gitroom

                                    04/24/2025

                                    Pretty slick honestly, swapping machines on Mac is usually a pain for me so this feels like a lifesaver.

                                  • sangpugogogo

                                    04/24/2025

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