mise shims resolve from cwd, not buffer path

jdtls was crashing with exit code 1 when I opened a Java file via fuzzy finder: the mise shim resolved Java from nvim’s startup directory instead of the project’s mise.toml.

What I Learned

The mise IDE integration docs recommend prepending shims to PATH for Neovim:

-- init.lua
vim.env.PATH = vim.env.HOME .. "/.local/share/mise/shims:" .. vim.env.PATH

This benefits all tools (Node, Python, Java, etc.), and I added it. But shims resolve tool versions based on the process’s cwd, not the buffer’s file path. When I launch nvim from ~ and use <leader>fp to open a file in a project directory, nvim’s cwd stays at ~. The fuzzy finder opens the file without calling :cd.

LSP servers spawned by nvim inherit this cwd. The Mason jdtls wrapper calls java -version to validate the JDK. The shim at ~/.local/share/mise/shims/java resolves from ~, finds no mise.toml with a Java version, and falls through to the system /usr/bin/java, which is broken on this machine.

The fix is a hybrid. The shims PATH stays (it is the mise-documented baseline and benefits all tools). For LSP servers specifically, I resolve the tool path from the project root inside the root_dir(bufnr, on_dir) callback, before the server process spawns:

-- Resolve JAVA_HOME from the project root via mise.
-- root_dir resolves from the buffer's file path, not nvim's cwd.
local function set_java_home(dir)
  if vim.fn.executable("mise") ~= 1 then
    return
  end
  local result = vim.fn.systemlist("cd " .. vim.fn.shellescape(dir) .. " && mise where java 2>/dev/null")
  if result and result[1] and result[1] ~= "" then
    vim.env.JAVA_HOME = result[1]:gsub("[\n\r]", "")
  end
end

I call set_java_home(root) before on_dir(root), so JAVA_HOME is set before the jdtls process spawns. The Mason wrapper finds JAVA_HOME and uses $JAVA_HOME/bin/java. This works regardless of where nvim was launched, because root_dir resolves from the buffer’s file path.

The mise docs mention mise where as a way to find tool paths programmatically. Combining shims PATH (for general tool resolution) with per-project mise where calls inside LSP callbacks (for cwd-independent resolution) covers both cases.

The full jdtls config, including the root_dir gate that scopes jdtls to the Maven backend, is in Scoping nvim-jdtls to a Maven subproject in a polyglot LazyVim setup.

References

• mise IDE Integration. The official Neovim recommendation: prepend shims to PATH. Also documents the limitation: “Once you have launched the IDE, it won’t reload the environment variables or the PATH.”
• vim.lsp.enable(). Documents the root_dir(bufnr, on_dir) callback signature used to set JAVA_HOME before the server spawns.
• mise where. CLI command to resolve a tool’s install path for the current directory.