How to avoid these kind of errors? My understanding is that JETLS is not starting from my current environment. How to make it happen? Or do should I add DataFrames to the main julia environment?

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I use eglot in emacs with JETLS. My main julia environment does not have DataFrames. I make separate packages for each project and install DataFrames separately in each project. My config details below. For JETLS install, I’m using the documentation. Emacs init and Julia pkg details ;; Julia REPL (use-package julia-repl :ensure t :hook (julia-ts-mode . julia-repl-mode) :config (julia-repl-set-terminal-backend 'vterm) (setq julia-repl-executable-records '((default "julia" :basedir "/Users/foo/applications/julia/usr/share/julia/base/"))) (setq julia-repl-executable-key 'default) ) ;; ;; Eglot ;; (use-package sideline-eglot :ensure t :init (setq sideline-backends-right '(sideline-eglot))) ;; Set up the Language Server Protocol (LSP) servers using Eglot. (use-package eglot :ensure t :hook ((eglot-mode . sideline-mode) (ess-r-mode . eglot-ensure)) :commands (eglot-ensure eglot-rename eglot-format-buffer)) (with-eval-after-load 'eglot (add-to-list 'eglot-server-programs '(((julia-mode :language-id "julia") (julia-ts-mode :language-id "julia")) "jetls" "--threads=auto" "--" "serve" "--socket" :autoport)) (add-to-list 'eglot-server-programs '(ess-r-mode . ("R" "--slave" "--args" "-e" "languageserver::run()")))) (use-package consult-eglot :ensure t) (use-package consult-eglot-embark :ensure t) (with-eval-after-load 'embark (with-eval-after-load 'consult-eglot (require 'consult-eglot-embark) (consult-eglot-embark-mode))) (@v1.13) pkg> st Status `~/.julia/environments/v1.13/Project.toml` [2b0e0bc5] LanguageServer v6.0.1 [295af30f] Revise v3.17.2 (@v1.13) pkg> app status [a3b70258] JETLS v2026.10.4 `https://github.com/aviatesk/JETLS.jl#release` jetls ~/applications/julia/usr/bin/julia [62bfec6d] Runic v1.13.0 git-runic ~/applications/julia/usr/bin/julia runic ~/applications/julia/usr/bin/julia

Thanks for this. I think I understand the issue, I have to add using DataFrames in the top. JETLS does not understand that the file is part of a package that uses DataFrames. I guess this is how it works?

I’m still confused as to how to edit a package where .jl files use structs and functions declared outside Base.

[image] mahmah: JETLS does not understand that the file is part of a package that uses DataFrames. I guess this is how it works? Well, I work with packages and have nearly nothing in the global environment, and JETLS finds the packages of Project.toml in the project root folder just fine. It needs some startup time, though, can be minutes. I use VSCode where you can follow the startup of JETLS in the status bar. It needs to instantiate the project to be able to work. Check manually that using Pkg Pkg.resolve() Pkg.instantiate() works. I don’t know how to debug JETLS startup issues with EMACS.

Thanks! About the last three commands, do they need to be added to the file I’m editing in JETLS or to the current environment?

[image] mahmah: About the last three commands, do they need to be added to the file I’m editing in JETLS or to the current environment? No. Just instantiate the project once in the REPL. But thats what you have to do anyways if you work with projects, if you use JETLS or not. If you want to learn how to work with projects, have a look at Working with Julia projects | Julia programming notes

Question: Even if your jl files are under the src/ folder, but the packages are in the main folder of the project, you don’t have any issue with using?

[image] mahmah: you don’t have any issue with using No, I don’t. Project.toml has to be in the root folder. JETLS needs to know where the root folder is, but as long as I use VSCode it knows that automatically. JETLS normally determines the workspace/project root from the editor’s LSP initialization: the editor searches upward from the opened Julia file for a root marker such as Project.toml, then tells JETLS that directory is the workspace root. How it resolves the root Editor-provided workspace root: VS Code, Neovim, Emacs, etc. usually use root markers. A typical Neovim configuration uses root_markers = { "Project.toml", "JuliaProject.toml" }; another example searches for Project.toml or .git. Nearest Project.toml: For analysis, JETLS determines each file’s package/project context from the nearest Project.toml above that file, independent of the current working directory. Package versus script mode: If the nearest project is a package directory—its Project.toml has a name entry—JETLS treats it as package mode and uses src/ .jl as the package entry file. Perhaps your Project.toml file has no name entry? Or you have no src/ .jl file?

Thanks. That question was for @George9000 .

JETLS: `DataFrame` is not defined

New to Julia

George9000 October 12, 2026, 2:12pm 2

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JETLS: `DataFrame` is not defined

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