How to explicitly disable lsp from running in a certain mode?

[ianyepan]

Lately, I've been trying to set up Processing in Emacs (.pde files), which has a major-mode of processing-mode whose parent-mode is java-mode. I've added hooks to run lsp when entering java-mode, but I don't want lsp to run in processing-mode. However, due to the parent-child relationship, lsp will try to run in processing-mode as well, and report errors as follows:

Warning (lsp-mode): Unable to calculate the languageId for buffer ‘fluid_coding_train.pde’. Take a look at ‘lsp-language-id-configuration’. The ‘major-mode’ is processing-mode
Warning (lsp-mode): Unable to calculate the languageId for buffer ‘fluid_coding_train.pde’. Take a look at ‘lsp-language-id-configuration’. The ‘major-mode’ is processing-mode
Warning (lsp-mode): Unable to calculate the languageId for buffer ‘fluid_coding_train.pde’. Take a look at ‘lsp-language-id-configuration’. The ‘major-mode’ is processing-mode
Warning (lsp-mode): Unable to calculate the languageId for buffer ‘fluid_coding_train.pde’. Take a look at ‘lsp-language-id-configuration’. The ‘major-mode’ is processing-mode
Warning (lsp-mode): Unable to calculate the languageId for buffer ‘fluid_coding_train.pde’. Take a look at ‘lsp-language-id-configuration’. The ‘major-mode’ is processing-mode
Warning (lsp-mode): Unable to calculate the languageId for buffer ‘fluid_coding_train.pde’. Take a look at ‘lsp-language-id-configuration’. The ‘major-mode’ is processing-mode

How can I explicitly disable lsp from processing-mode, yet keeping it running for java-mode?

[yyoncho]

You can have a wrapper of lsp which does (when (eq major-mode whatever) (lsp)) and use it for your hooks.

[ianyepan]

Awesome, I solved it like so:

(add-hook 'java-mode-hook #'(lambda () (when (eq major-mode 'java-mode) (lsp-deferred))))

The slightly unfortunate aspect is that I can't group with the rest of my use-package hooks like so:

:hook ((c-mode          ; clangd
        c++-mode        ; clangd
        c-or-c++-mode   ; clangd
        ;; java-mode       ; eclipse-jdtls
        js-mode         ; ts-ls (tsserver wrapper)
        js-jsx-mode     ; ts-ls (tsserver wrapper)
        typescript-mode ; ts-ls (tsserver wrapper)
        python-mode     ; pyright
        web-mode        ; ts-ls/HTML/CSS
        haskell-mode    ; haskell-language-server
        lua-mode        ; lua-language-server
        ) . lsp-deferred)