Possible race condition with mason v2

[WhoIsSethDaniel]

Hi. I maintain mason-tool-installer and I'm seeing a potential race condition re: mason v2.

mason-tool-installer calls mason-registry.refresh(callback) and the callback calls mason-lspconfig.get_mappings(). At this point I (sometimes) get the error:

vim.schedule callback: ...ins/opt/mason.nvim/lua/mason-registry/sources/github.lua:56: Expected value but found T_END at character 1
stack traceback:
        [C]: in function 'decode'
        ...ins/opt/mason.nvim/lua/mason-registry/sources/github.lua:56: in function 'get_all_package_specs'
        ...k/git-plugins/opt/mason.nvim/lua/mason-registry/init.lua:77: in function 'get_all_package_specs'
        ...pt/mason-lspconfig.nvim/lua/mason-lspconfig/mappings.lua:9: in function 'get_mason_map'
        ...pt/mason-lspconfig.nvim/lua/mason-lspconfig/mappings.lua:42: in function 'get_mappings'
        ...on-tool-installer.nvim/lua/mason-tool-installer/init.lua:178: in function 'ensure_installed'
        ...on-tool-installer.nvim/lua/mason-tool-installer/init.lua:276: in function ''
        vim/_editor.lua: in function ''
        vim/_editor.lua: in function <vim/_editor.lua:0>

The error suggests to me that the JSON has been overwritten and is still 0 bytes long at the time mason-tool-installer calls get_mappings().

If I look at the mason log (set to DEBUG) I see:

[DEBUG Wed 07 May 2025 03:13:44 PM CDT] ...k/git-plugins/opt/mason.nvim/lua/mason-registry/init.lua:138: Refreshing the registry.
[DEBUG Wed 07 May 2025 03:13:44 PM CDT] ...k/git-plugins/opt/mason.nvim/lua/mason-registry/init.lua:106: Updating the registry.
[DEBUG Wed 07 May 2025 03:13:44 PM CDT] ...-plugins/opt/mason.nvim/lua/mason-registry/installer.lua:38: Installing registries. LazySourceCollection(list={LazySource(type=lua, id=mason-registry.index), LazySource(type=github, id=mason-org/mason-registry)})
[DEBUG Wed 07 May 2025 03:13:44 PM CDT] ...pack/git-plugins/opt/mason.nvim/lua/mason-core/fetch.lua:37: Fetching URL "https://api.mason-registry.dev/api/github/mason-org/mason-registry/releases/latest"
[DEBUG Wed 07 May 2025 03:13:44 PM CDT] ...ck/git-plugins/opt/mason.nvim/lua/mason-core/process.lua:189: Spawning cmd="curl", spawn_opts={
  args = { "-H", "Accept: application/vnd.mason-registry.v1+json; q=1.0, application/json; q=0.8", "-H", "User-Agent: mason.nvim v2.0.0 (+https://github.com/mason-org/mason.nvim)", "-fsSL", "-X", "GET", "--connect-timeout", 30, "https://api.mason-registry.dev/api/github/mason-org/mason-registry/releases/latest" }
}
[DEBUG Wed 07 May 2025 03:13:44 PM CDT] ...ck/git-plugins/opt/mason.nvim/lua/mason-core/process.lua:235: Spawned with pid 128013
[DEBUG Wed 07 May 2025 03:13:45 PM CDT] ...ck/git-plugins/opt/mason.nvim/lua/mason-core/process.lua:221: Job pid=128013 exited with exit_code=0, signal=0
[DEBUG Wed 07 May 2025 03:13:45 PM CDT] ...pack/git-plugins/opt/mason.nvim/lua/mason-core/fetch.lua:37: Fetching URL "https://github.com/mason-org/mason-registry/releases/download/2025-05-07-frayed-tank/registry.json.zip"
[DEBUG Wed 07 May 2025 03:13:45 PM CDT] ...ck/git-plugins/opt/mason.nvim/lua/mason-core/process.lua:189: Spawning cmd="curl", spawn_opts={
  args = { "-H", "User-Agent: mason.nvim v2.0.0 (+https://github.com/mason-org/mason.nvim)", "-fsSL", "-X", "GET", "-o", "/home/seth/.local/share/nvim/mason/registries/github/mason-org/mason-registry/registry.json.zip", "--connect-timeout", 30, "https://github.com/mason-org/mason-registry/releases/download/2025-05-07-frayed-tank/registry.json.zip" }
}
[DEBUG Wed 07 May 2025 03:13:45 PM CDT] ...ck/git-plugins/opt/mason.nvim/lua/mason-core/process.lua:235: Spawned with pid 128047
[DEBUG Wed 07 May 2025 03:13:45 PM CDT] ...ck/git-plugins/opt/mason.nvim/lua/mason-core/process.lua:221: Job pid=128047 exited with exit_code=0, signal=0
[DEBUG Wed 07 May 2025 03:13:45 PM CDT] ...im/pack/git-plugins/opt/mason.nvim/lua/mason-core/fs.lua:59: fs: unlink /home/seth/.local/share/nvim/mason/registries/github/mason-org/mason-registry/registry.json.zip
[DEBUG Wed 07 May 2025 03:13:45 PM CDT] ...pack/git-plugins/opt/mason.nvim/lua/mason-core/fetch.lua:37: Fetching URL "https://github.com/mason-org/mason-registry/releases/download/2025-05-07-frayed-tank/checksums.txt"
[DEBUG Wed 07 May 2025 03:13:45 PM CDT] ...ck/git-plugins/opt/mason.nvim/lua/mason-core/process.lua:189: Spawning cmd="curl", spawn_opts={
  args = { "-H", "User-Agent: mason.nvim v2.0.0 (+https://github.com/mason-org/mason.nvim)", "-fsSL", "-X", "GET", "--connect-timeout", 30, "https://github.com/mason-org/mason-registry/releases/download/2025-05-07-frayed-tank/checksums.txt" }
}
[DEBUG Wed 07 May 2025 03:13:45 PM CDT] ...ck/git-plugins/opt/mason.nvim/lua/mason-core/process.lua:235: Spawned with pid 128050
[DEBUG Wed 07 May 2025 03:13:45 PM CDT] ...k/git-plugins/opt/mason.nvim/lua/mason-registry/init.lua:138: Refreshing the registry.
[DEBUG Wed 07 May 2025 03:13:45 PM CDT] ...k/git-plugins/opt/mason.nvim/lua/mason-registry/init.lua:147: Registry refresh is not necessary yet. Registry age=269, checksum="1bc609de879b19cd437d41eff2c15b3bf17e7a5b1a6c1dc32845cffa270253ea"
[DEBUG Wed 07 May 2025 03:13:47 PM CDT] ...ck/git-plugins/opt/mason.nvim/lua/mason-core/process.lua:221: Job pid=128050 exited with exit_code=0, signal=0
[DEBUG Wed 07 May 2025 03:13:47 PM CDT] ...k/git-plugins/opt/mason.nvim/lua/mason-registry/init.lua:138: Refreshing the registry.
[DEBUG Wed 07 May 2025 03:13:47 PM CDT] ...k/git-plugins/opt/mason.nvim/lua/mason-registry/init.lua:147: Registry refresh is not necessary yet. Registry age=271, checksum="1bc609de879b19cd437d41eff2c15b3bf17e7a5b1a6c1dc32845cffa270253ea"

I can say that this never occurred with v1, but I realize I may need to make a change on my end for v2. Or maybe this is a race condition in v2. My question is: which, if either of those possibilities, is it?

I can provide a lot more information if needed. I just need to know what is required. Thanks.

[WhoIsSethDaniel]

It looks like I had an (older?) entry in the registries part of the config. As of now it seems this is what was causing the problem.

      registries = {
        'lua:mason-registry.index',
        'github:mason-org/mason-registry',
      },

It's the first entry that I have now removed.