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ghcide/docs/Setup.md
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1# Setup Troubleshooting
3This page serves as a dumping ground for setup problems and their resolutions. We recommend everyone first runs `ghcide` on the console to check what files in their project load, and only the moves on to using `ghcide` through an editor (e.g. VS Code).
5## "mismatched interface file versions"
7If you see a problem such as:
9```console
10File: ./test/Spec.hs
11Range: 1:0-1:0
12Source: typecheck
13Severity: DsError
14Message:
15 test/Spec.hs:1:1: error:
16 Bad interface file:
17 /Users/daml/.stack/programs/x86_64-osx/ghc-8.6.4/lib/ghc-8.6.4/base-4.12.0.0/Prelude.hi
18 mismatched interface file versions (wanted "8065", got "8064")
19```
21The cause is that your program is configured to use a different GHC to the one you built `ghcide` with. In `ghcide` you can view the version number it was compiled with on the first line as:
23```console
24ghcide version: 0.0.3 (GHC: 8.6.5)
25```
27You can see the version of GHC being used by this project in the second-last line of the output with `ghc-8.6.4/`, or in in mismatch interfaces of wanted `8065` (aka 8.6.5), got `8064` (aka 8.6.4). The solution is to use the same GHC version in both places.
29## Works in `ghcide` but not my editor
31Does `ghcide` alone work on the console? Did you first enter a Nix shell? Or run `stack exec ghcide`? If so, there are two options:
331. Run your editor via the same mechanism, e.g. `stack exec code`.
342. Change the extension to use the executable as `stack` and the arguments as `exec -- ghcide --lsp`.
36## Issues with Nix
38If you are using packages installed by Nix, then often Nix will set `NIX_GHC_LIBDIR` to say where the libraries are installed. `ghcide` can cope with that. However, sometimes the `ghc` on your shell will actually be a shell script that sets `NIX_GHC_LIBDIR`, which `ghcide` can't find. If that happens, you need to either set `NIX_GHC_LIBDIR` (so `ghcide` can see it) or use a proper [Nix compatible wrapper](https://github.com/hercules-ci/ghcide-nix) over `ghcide`.
40## Symbol’s value as variable is void: capability
42As described [here](https://github.com/emacs-lsp/lsp-mode/issues/770#issuecomment-483540119) and [here](https://github.com/emacs-lsp/lsp-mode/issues/517#issuecomment-445448700), the default installation of `lsp-mode`, `lsp-ui`, `lsp-ui-mode` and `lsp-haskell` as described in [ghcide's "Using with Emacs" section](https://github.com/digital-asset/ghcide/#using-with-emacs) may result in the following error message:
44```
45Symbol’s value as variable is void: capability
46```
48This can be caused by either an old version of the Emacs package `dash`, or a cached `.elc` file for an old version. A fix consists of (re)moving the old package from ~/.emacs.d/elpa/ and installing it again, e.g. via M-x `package-list-packages` RET and M-x `package-install` RET `dash` RET. If this is not enough,
50```
51find ~/.emacs.d -name '*.elc' -exec rm {} \;
52```
54(which causes recompilation of all bytecode-compiled scripts.)