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Re-model LSP JSON-RPC with core.async channels (clojure-lsp#1110)
This gives clients a uniform interface to conform to. They model messages as Clojure hashmaps, and put those messages to and take them from a pair of channels. This cleans up the tests slightly, but is actually prep for clojure-lsp/lsp4clj#8. We'll be able to use this code for both client and server communication. With tools to convert stdio to channels, we get a few benefits. 1. It will be easier to implement socket communication clojure-lsp/lsp4clj#1 as a complement to stdio communication. We'll need to write the code that converts socket i/o to channels, but the client (or actually server) won't change. 2. It will be easier to write mocks for tests. The tests (even unit tests) can read from and write to a server's channels to make assertions about how it responds without having to understand the wire level of the LSP JSON-RPC protocol. 3. There will be a natural mechanism for concurrency. Servers can choose to read several messages from a channel, distributing each to a pool of workers.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,97 @@ | ||
| (ns integration.lsp-json-rpc | ||
| "Models LSP JSON-RPC as core.async channels of messages (Clojure hashmaps). | ||
| https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#baseProtocol" | ||
| (:require | ||
| [cheshire.core :as json] | ||
| [clojure.core.async :as async] | ||
| [clojure.string :as string])) | ||
|
|
||
| (set! *warn-on-reflection* true) | ||
|
|
||
| (defn ^:private read-n-chars [^java.io.Reader reader content-length] | ||
| (let [cs (char-array content-length)] | ||
| (loop [total-read 0] | ||
| (when (< total-read content-length) | ||
| ;; FIXME: this is buggy. It reads `content-length` chars, but | ||
| ;; `content-length` is specified in bytes. It works as long as the | ||
| ;; integration tests are all in ASCII, but would break if they weren't. | ||
| ;; See https://github.com/mainej/lsp4clj/blob/lsp2clj/server/src/lsp4clj/json_rpc.clj | ||
| ;; for a correct implementation. The best way to fix this is probably to | ||
| ;; wait for that to be merged and then use those helpers. | ||
| (let [new-read (.read reader cs total-read (- content-length total-read))] | ||
| (when (< new-read 0) | ||
| ;; TODO: return nil instead? | ||
| (throw (java.io.EOFException.))) | ||
| (recur (+ total-read new-read))))) | ||
| (String. cs))) | ||
|
|
||
| (defn ^:private parse-header [line headers] | ||
| (let [[h v] (string/split line #":\s*" 2)] | ||
| (when-not (contains? #{"Content-Length" "Content-Type"} h) | ||
| (throw (ex-info "unexpected header" {:line line}))) | ||
| (assoc headers h v))) | ||
|
|
||
| (defn ^:private read-message [reader headers] | ||
| (let [content-length (parse-long (get headers "Content-Length")) | ||
| ;; TODO: handle content-type | ||
| content (read-n-chars reader content-length)] | ||
| (json/parse-string content true))) | ||
|
|
||
| (defn ^:private write-message [msg] | ||
| (let [content (json/generate-string msg)] | ||
| ;; FIXME: this is buggy. It sets `Content-Length` to the number of chars in | ||
| ;; the content, but `Content-Length` should be the number of bytes (encoded | ||
| ;; as UTF-8). The fix is the same as for `read-n-chars`: we should use the | ||
| ;; helpers provided by lsp4clj. | ||
| (print (str "Content-Length: " (.length content) "\r\n" | ||
| "\r\n" | ||
| content)) | ||
| (flush))) | ||
|
|
||
| (defn ^:private read-line-async | ||
| "Reads a line of input asynchronously. Returns a channel which will yield the | ||
| line when it is ready, or nil if the input has closed. Returns immediately. | ||
| Avoids blocking by reading in a separate thread." | ||
| [^java.io.BufferedReader input] | ||
| ;; we are agnostic about \r\n or \n because readLine is too | ||
| (async/thread (.readLine input))) | ||
|
|
||
| (defn buffered-reader->receiver-chan | ||
| "Returns a channel which will yield parsed messages that have been read off | ||
| the reader. When the reader is closed, closes the channel." | ||
| [^java.io.BufferedReader reader] | ||
| (let [msgs (async/chan 1)] | ||
| (async/go-loop [headers {}] | ||
| (if-let [line (async/<! (read-line-async reader))] | ||
| (if (string/blank? line) ;; a blank line after the headers indicate start of message | ||
| (do (async/>! msgs (read-message reader headers)) | ||
| (recur {})) | ||
| (recur (parse-header line headers))) | ||
| ;; input closed; also close channel | ||
| (async/close! msgs))) | ||
| msgs)) | ||
|
|
||
| (defn buffered-writer->sender-chan | ||
| "Returns a channel which expects to have messages put on it. nil values are | ||
| not allowed. Serializes and writes the messages to the writer. When the | ||
| channel is closed, closes the writer." | ||
| [^java.io.BufferedWriter writer] | ||
| (let [messages (async/chan 1)] | ||
| (binding [*out* writer] | ||
| (async/go-loop [] | ||
| (if-let [msg (async/<! messages)] | ||
| (do | ||
| (write-message msg) | ||
| (recur)) | ||
| ;; channel closed; also close writer | ||
| (.close writer)))) | ||
| messages)) | ||
|
|
||
| (defn json-rpc-message | ||
| ([method params] ;; notification | ||
| {:jsonrpc "2.0" | ||
| :method method | ||
| :params params}) | ||
| ([id method params] ;; request | ||
| (assoc (json-rpc-message method params) :id id))) |