Shortening startup time

[HardoMX]

I am working on speeding up my startup, and have cut it down a lot. Currently DAP is the slowest part, and specifically dap.ext.vscode is the slow part.

dap.ext.vscode takes between 40 and 50ms to execute, is it possible to speed this up, and if so, how? What influences the time dap.ext.vscode takes to execute?

output from --startuptime containing all DAP-related parts:

038.654  000.085  000.085: sourcing /home/arch/.local/share/nvim/lazy/nvim-dap/plugin/dap.lua
039.192  000.048  000.048: require('dap.utils')
039.313  000.650  000.602: require('dap')
040.304  000.192  000.192: require('nio.tasks')
040.349  000.042  000.042: require('nio.control')
040.513  000.163  000.163: require('nio.uv')
040.562  000.047  000.047: require('nio.tests')
040.651  000.044  000.044: require('vim.ui')
040.660  000.096  000.052: require('nio.ui')
040.750  000.050  000.050: require('nio.streams')
040.751  000.090  000.040: require('nio.file')
040.877  000.035  000.035: require('nio.util')
040.931  000.134  000.099: require('nio.logger')
040.941  000.189  000.055: require('nio.lsp')
040.995  000.053  000.053: require('nio.process')
041.009  001.307  000.434: require('nio')
041.367  000.083  000.083: require('dapui.config.highlights')
041.567  000.427  000.344: require('dapui.config')
041.575  000.500  000.073: require('dapui.util')
041.637  000.061  000.061: require('dapui.windows.layout')
041.642  000.631  000.070: require('dapui.windows')
041.709  000.066  000.066: require('dapui.controls')
041.715  002.400  000.396: require('dapui')
042.016  000.085  000.085: require('dapui.client.types')
042.020  000.145  000.060: require('dapui.client')
042.088  000.067  000.067: require('dap.breakpoints')
042.153  000.052  000.052: require('dapui.client.lib')
042.275  000.066  000.066: require('dapui.render.canvas')
042.278  000.115  000.048: require('dapui.elements.breakpoints')
042.360  000.055  000.055: require('dapui.components.breakpoints')
042.437  000.048  000.048: require('dapui.elements.repl')
042.480  000.041  000.041: require('dapui.elements.scopes')
042.541  000.045  000.045: require('dapui.components.scopes')
042.591  000.049  000.049: require('dapui.components.variables')
042.646  000.041  000.041: require('dapui.elements.stacks')
042.757  000.042  000.042: require('dapui.components.frames')
042.759  000.095  000.053: require('dapui.components.threads')
042.829  000.045  000.045: require('dapui.elements.watches')
042.894  000.049  000.049: require('dapui.components.watches')
042.956  000.042  000.042: require('dapui.elements.hover')
043.011  000.040  000.040: require('dapui.components.hover')
043.064  000.046  000.046: require('dapui.elements.console')
043.429  000.287  000.287: require('nvim-dap-virtual-text')
044.127  000.216  000.216: require('nvim-dap-repl-highlights.utils')
044.130  000.646  000.430: require('nvim-dap-repl-highlights')
084.482  046.349  041.307: require('dap.ext.vscode')
084.782  000.292  000.292: require('mason-nvim-dap.mappings.filetypes')
085.209  000.172  000.172: require('mason-core.notify')
085.370  000.158  000.158: require('mason-core.functional.number')
085.419  000.538  000.209: require('mason-nvim-dap.api.command')

[mfussenegger]

Not sure why dap.ext.vscode would take so long, for me it takes around ~1ms - similar to other modules. It's not that large and doesn't do anything special on import.

That said, you could probably defer all the imports - maybe with the exception of dap itself - to first-use when you start a debug session. The dap module itself takes care to lazy-load everything else until a session gets started.

Calling require('dap.ext.vscode') in particular shouldn't be required anymore since #1237

[HardoMX]

I have no idea why it is taking so long, maybe it is some way i've done the config? I am not calling require(dap.ext.vscode) manually, so some DAP or extension is doing so.

What would be the best way to lazy load DAP? Is there a fitting event to use with Lazy, or is it done through DAP itself?

This is my dap.lua:

return {
    "mfussenegger/nvim-dap",
    dependencies = {
        "rcarriga/nvim-dap-ui",
        "nvim-neotest/nvim-nio",
        "theHamsta/nvim-dap-virtual-text",
        "LiadOz/nvim-dap-repl-highlights",
    },
    config = function()
        local dap = require("dap")
        local ui = require("dapui")

        ui.setup()
        require("nvim-dap-virtual-text").setup()
        require("nvim-dap-repl-highlights").setup()

        require("nvim-treesitter.configs").setup({
            ensure_installed = { "dap_repl" }
        })

        -- DAPs using mason are set up and configured in lua.plugins.lsp.mason.lua

        -- Install local-lua-debugger-vscode
        dap.adapters["local-lua"] = {
            type = "executable",
            command = "local-lua-dbg", -- INFO: If you install via a package manager, otherwise change this for comment bellow
            -- command = "node",
            -- args = { "/usr/lib/node_modules/local-lua-debugger-vscode/extension/debugAdapter.js" },
            enrich_config = function(config, on_config)
                if not config["extensionPath"] then
                    local c = vim.deepcopy(config)
                    c.extensionPath = "/usr/lib/node_modules/local-lua-debugger-vscode/"
                    on_config(c)
                else
                    on_config(config)
                end
            end
        }
        dap.configurations.lua = {
            {
                type = "local-lua",
                name = "lua-dgb",
                request = "launch",
                cwd = "${workspaceFolder}",
                program = {
                    lua = "lua",
                    file = "${file}"
                }
            }
        }


        -- Configure bashdb (Installed through Mason)
        -- If my pull request to mason-nvim-dap is approved this will no longer be necessary
        dap.adapters.bashdb = {
            type = "executable",
            command = vim.fn.stdpath("data") .. "/mason/packages/bash-debug-adapter/bash-debug-adapter",
            name = "bashdb"
        }
        dap.configurations.sh = {
            {
                type = 'bashdb',
                request = 'launch',
                name = "Launch file",
                showDebugOutput = true,
                pathBashdb = vim.fn.stdpath("data") .. '/mason/packages/bash-debug-adapter/extension/bashdb_dir/bashdb',
                pathBashdbLib = vim.fn.stdpath("data") .. '/mason/packages/bash-debug-adapter/extension/bashdb_dir',
                trace = true,
                file = "${file}",
                program = "${file}",
                cwd = '${workspaceFolder}',
                pathCat = "cat",
                pathBash = "/bin/bash",
                pathMkfifo = "mkfifo",
                pathPkill = "pkill",
                args = {},
                env = {},
                terminalKind = "integrated"
            }
        }


        -- Configure Firefox to ask for url and port
        dap.adapters.firefox = {
            type = "executable",
            command = vim.fn.exepath('firefox-debug-adapter'),
        }
        dap.configurations.firefox = {
            {
                name = "Debug",
                type = "firefox",
                request = "launch",
                reAttach = true,
                url = function()
                    return vim.fn.input("URL: ", "http://localhost:")
                end,
                webRoot = "${workspaceFolder}",
                firefoxExecutable = vim.fn.exepath("firefox"),
            }
        }
    end
}

Except for lua, mason handles the install of DAPs.

[HardoMX]

dap.ext.vscode seems to have something to do with mason-nvim-dap.nvim. When I remove mason-nvim-dap dap.ext.vscode is not even present in the startuptime output.

Since I only used mason-nvim-dap for automatically installing DAPs, I instead just wrote a custom function for doing that and removed mason-nvim-dap.

I am still interested if I could Lazy load the entirety of nvim-dap, and if so, what event to use, but this function will suffice for now.

[mfussenegger]

I'm not sure at what point dapui, virtual-text and repl-highlights need to be setup.

I think one option you could try is to move the initialization of the extensions into a on_config hook. The on_config hook is called shortly before a debug session starts after you've selected a configuration, either via dap.continue(), :DapNew or via dap.run(config), so it should be early enough for the extension to register their own listeners if needed, unless they also setup on_config hooks themselves, but I think the plugins you mentioned don't do that.

local dap = require("dap")
dap.listeners.on_config["my_conf_setup"] = function(config)

  require("dapui").setup()
  require("nvim-dap-repl-highlights").setup()
  require("nvim-treesitter.configs").setup({
      ensure_installed = { "dap_repl" }
  })

  -- unregister to make sure this is only run once
  dap.listeners.on_config["my_conf_setup"] = nil
  return config
end

That said, this is a bit of a workaround. Ideally you'd raise issues with the extensions so that a require("...").setup() call doesn't eagerly load all their dependencies.

[HardoMX]

Apparently my own function did not remove dap.ext.vscode from taking so long, however I have managed to speed up the loading time, so I'll leave it at that.

If I have the time I might sift through my config and logs more to find the underlying issue, but for now this is enough 🙂

I'll see if I can move some things to a on_config() function tho.

[HardoMX]

So, changing from mason-nvim-dap to using my own function to "ensure_installed" hasn't removed the dap.ext.vscode issue, but has reduced startuptime enough anyways. I might come back to this with snacks.profiler and do a really thorough inspection, but for now I'll leave this issue.