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README.langserver.md

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Running Kythe Langserver

Note: Below only tested for serving Go code.

Building

Build the binary, then place it somewhere on your path.

bazel build kythe/go/languageserver/...
cp -f bazel-bin/kythe/go/languageserver/kythe_languageserver ~/bin/

Preparing vim-lsp

Put the following snippet in your .vimrc:

if executable('kythe_languageserver')
    au User lsp_setup call lsp#register_server({
        \ 'name': 'kythe_languageserver',
        \ 'cmd': {server_info->['kythe_languageserver']},
        \ 'allowlist': ['go'],
        \ })
endif

Prepare and serve a Kythe index

This is a complicated topic, but in a nutshell:

# index.sh
# Argument to script: bazel target (for example //kythe/go/...).
GS=/tmp/kgs
TAB=/tmp/ktab
ENTRIES=/tmp/entries

rm -rf $GS $TAB bazel-out/k8-fastbuild/extra_actions

# Extract go compilations.
bazel build $1 --experimental_action_listener kythe/go/extractors/cmd/bazel:extract_kzip_go

# Write index entries to graphstore.
bazel-bin/kythe/go/indexer/cmd/go_indexer/go_indexer -code $(find bazel-out/k8-fastbuild/extra_actions -name '*.kzip' | xargs -n1 readlink -f) > $ENTRIES

# Prepare serving tables.
# Need to use Beam pipeline, the legacy one won't serve documentation properly.
# See https://github.com/kythe/kythe/issues/3412.
bazel-bin/kythe/go/serving/tools/write_tables/write_tables --entries $ENTRIES --experimental_beam_pipeline --out $TAB

# Serve.  ("--listen :8080" allows access from other machines)
bazel-bin/kythe/go/serving/tools/http_server/http_server --serving_table $TAB --listen localhost:8080

Augment the local-to-vname mapping

If needed, tune .kythe_settings.json. The Kythe repo now contains a sensible default for //kythe/go/....

Generally, strive to make the corpus+root prefixes unambigous during your extraction (can be controlled by vnames.json, see kythe#3394).

Note that matching using .kythe_settings.json is bidirectional and stops at the first match. If your prefixes are ambiguous (for example due to having both empty and non-empty root in the same corpus), pay extra attention to the ordering.

Use vim-lsp

Start up vim on a go source file. Use :LspHover to get doc and type info about the entity under the cursor, :LspDefinition to jump to def, :LspReferences to find all backreferences.

Check the langserver status with :LspStatus.

To debug the langserver output, execute:

tail $(lsof -p $(ps ax | grep kythe_languageserver | grep -v grep | awk '{print $1}') | grep 'log$' | awk '{print $NF}')

Finding references and navigating virtual files.

By using above procedure you can navigate the physical source files. But generated sources and sources pulled from external workspaces, such as github repos, won't be navigable. Moreover, when you look for references on an entity, and such a reference resides in a non-physical file, vim-lsp will fail to open the file (likely to get snippets) and not display any results.

But worry not! You can use the kythefs tool to mount the files in a Kythe index using a virtual filesystem. After installing fuse, the user-space filesystem utility, for your distribution:

bazel build kythe/go/serving/tools/kythefs
# Will block until unmounted with `fusermount -u vfs`
./bazel-bin/kythe/go/serving/tools/kythefs/kythefs --mountpoint vfs

The default .kythe_settings.json already configures the virtual files to be mapped to the vfs directory in the workspace root, so this should "just work" (to the extent anything just works usually).

Note: if the vfs directory is in your workspace, might hog scanning commands like git status or editors. Probably you can do some trickery by moving both the vfs directory and .kythe_settings.json one level up.