I think it's failing to parse CodeAction result while doing the Format. CodeAction.command should be of type Command (not string) according to the spec. However, CodeAction result can be (Command | CodeAction)[] | null, so maybe it's returning a Command instead of a CodeAction? It's hard to know what's going on without looking at the RPC trace. There may be a flag in clojure-lsp to print the json-rpc protocol trace.

I'll try to investigate clojure-lsp side when I can get some time. Acme + acme-lsp is a very compelling tool!

Looks like clojure-lsp is utilizing the library lsp4j. I was able to get RPC tracing of the calls to log. Here is what happens on a call to "L fmt".

1. I updated clojure-lsp to the latest and now receive this error when calling "L fmt"
   2020/01/06 23:12:21 The accessor 'CodeActionContext.getDiagnostics()' must return a non-null value. Path: $.params.context.diagnostics L: exit 1

2. The clojure-lsp tracing receives a textDocument/didChange although nothing changed.
   [Trace - 11:11:24 PM] Received notification 'textDocument/didChange' Params: { "textDocument": { "version": 0, "uri": "file:///Users/scott/Projects/Clojure/fiat-hell/src/fiat_hell/money.clj" }, "contentChanges": [ { "text": omitting the rest of the document trace here

3. There are no further commands received to format the document. This is different than when running the "L hov" command - which works. The L hov command also first sends a textDocument/didChange request, but then follows it up with this:
   [Trace - 11:17:00 PM] Received request 'textDocument/hover - (18)' Params: { "textDocument": { "uri": "file:///Users/scott/Projects/Clojure/fiat-hell/src/fiat_hell/money.clj" }, "position": { "line": 6, "character": 14 } }

4. Diagnostics work fine.

5. "L comp" gives this error
   2020/01/06 23:21:50 The accessor 'CompletionContext.getTriggerKind()' must return a non-null value. Path: $.params.context.triggerKind L: exit 1

thanks for any suggestions you may have

I've added a -rpc.trace flag to acme-lsp for easier debugging. I was able to reproduce your problems. To summarize:

• L fmt: textDocument/codeAction is returning []Command instead of []CodeAction
• L def: textDocument/definition is returning Location instead of []Location
• L comp: textDocument/completion is returning CompletionItem[] instead of CompletionList

clojure-lsp is allowed to return those according to the spec. It just differs from gopls, which is what acme-lsp LSP parser is based on. The first two are probably not easy to fix. Completion should be relatively easy to fix by converting the CompletionItem[] to a CompletionList during JSON unmarshal.

I'm not sure when I'll get around to looking deeper. If anyone wants to work on fixes, PRs are welcome. There are some workarounds to these types of JSON unmarshaling issues (see internal/lsp/protocol/compat.go), but in general it's not fun trying to unmarshal JSON union types in Go.