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🔀 Merge chore/protocol-backed-lsp-helper into main
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tmu committed 2026-09-18 07:45:22 +00:00
2 parents 6f87c2f3b5 947eac8089
commit 62c37e6d89
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backlog.tasks
+8 -1
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@@ -32,6 +32,11 @@ Testing:
→ `src/util/__tests__/lsp-completion.ts` (`#test-utils/…`) is the helper; the suite asserts its labels (see development/testing.md § Autocomplete)
→ wire it into `node --test` so a test asserts the offered labels
→ note: `Parameters<typeof factory>[0]` resolves only the *last* overload; use `@ts-expect-error` call sites for factory negatives, not `not.toExtend<Parameters<…>>`
✔ Drive the LSP completion helper through the LSP protocol library instead of a hand-rolled JSON-RPC client @medium @done
✔ Add `vscode-languageserver-protocol` and record the tooling decision @done
✔ Rewrite `src/util/__tests__/lsp-completion.ts` onto `createMessageConnection` and typed requests @done
✔ Update `development/testing.md § Autocomplete` for the new client @done
✔ Run `npm run verify` and check the task off @done
Matcher:
✔ Clean up: adopt the 3-overload matcher (`src/prototype-ac2.ts`) and delete the prototypes @high @done
@@ -43,7 +48,9 @@ Matcher:
→ `{ a, b, _ }` for `T = "a" | "b"` is accepted today; the redundant `_` should be rejected
Bugs:
✔ TS 7 LSP server logs `context canceled` on stderr at shutdown @done
→ `handleExit` returns `io.EOF`, cancelling the background context while `Session.updateWatches` is still in flight; the bare error is flushed to stderr and the server exits 1
→ close stdin after `shutdown` instead of sending `exit`; the server exits cleanly (code 0, no output), kill kept as a fallback
Enhancements:
☐ Allow boolean literals in primitive union patterns (e.g. `true: () => "yes"`) @medium
☐ Are there other primitive types that should be supported in union patterns? (e.g. `bigint`, `symbol`) @medium
development/tooling.md
+34
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@@ -24,6 +24,8 @@ in [package.json](../package.json).
- **@spences10/pi-lsp** — read-only LSP code intelligence for AI agents
(project-local `.pi/settings.json`); talks to this repo's TypeScript 7 via
`tsc --lsp --stdio`.
- **vscode-languageserver-protocol** — LSP client and protocol types for the
autocomplete test helper (`src/util/__tests__/lsp-completion.ts`).
When each runs is in
[CONTRIBUTING.md § Feedback tiers](../CONTRIBUTING.md#feedback-tiers).
@@ -247,6 +249,38 @@ project.
- The same script works by hand (whole project) and staged (scoped), so there is
no second command to maintain.
## Language server tooling
### `vscode-languageserver-protocol` backs the autocomplete helper
#### Decision (2026-09)
The autocomplete helper (`src/util/__tests__/lsp-completion.ts`) drives
`tsc --lsp --stdio` through `vscode-languageserver-protocol`'s
`createMessageConnection` and its typed request / notification objects, instead
of a hand-rolled JSON-RPC client.
#### Why
- Framing, `Content-Length` parsing, the pending-request map and server-request
dispatch are protocol plumbing the helper only reimplemented; the official
client owns them and tolerates the server's `string | number` ids.
- `InitializeRequest`, `CompletionRequest`, `DidOpenTextDocumentNotification`,
… carry their parameter and result types, so `CompletionList` / `CompletionItem`
replace the helper's ad-hoc shape guards.
- The `./node` entry re-exports `vscode-jsonrpc/node`, so one devDependency
supplies both the transport and the protocol types. It is test-only and never
ships (`files` publishes `dist/` only).
#### Rejected
- `vscode-languageclient`: the editor-side client with a full feature registry
— far more than a test helper needs.
- Generic JSON-RPC (`jsonrpc-lite`, `jayson`): still no LSP types, so they
replace framing only and leave the typed protocol surface unimplemented.
- Keeping the hand-rolled client: the low-level shape is the maintenance cost
the helper exists to remove, and it must be re-audited against the server.
## Editor and agent tooling
### VSCode integration
package-lock.json
Generated
+30 -1
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@@ -27,7 +27,8 @@
"oxlint": "^1.83.0",
"oxlint-tsgolint": "^7.0.2001",
"publint": "^0.3.24",
"typescript": "^7.0.2"
"typescript": "^7.0.2",
"vscode-languageserver-protocol": "^3.18.3"
},
"engines": {
"node": ">=26"
@@ -4822,6 +4823,27 @@
"node": "^14.17.0 || ^16.13.0 || >=18.0.0"
}
},
"node_modules/vscode-jsonrpc": {
"version": "9.0.2",
"resolved": "https://registry.npmjs.org/vscode-jsonrpc/-/vscode-jsonrpc-9.0.2.tgz",
"integrity": "sha512-SbQSV9yRemARxeXw6LU5sS6Zq0e9/DgCCX5yelH263ZQWukbTk8EF8fjTrr1dziasf4GwlJbvTwFnTrnQFWZXQ==",
"dev": true,
"license": "MIT",
"engines": {
"node": ">=14.0.0"
}
},
"node_modules/vscode-languageserver-protocol": {
"version": "3.18.3",
"resolved": "https://registry.npmjs.org/vscode-languageserver-protocol/-/vscode-languageserver-protocol-3.18.3.tgz",
"integrity": "sha512-DF49+WeV5py4zO5hhobp60jjsDSK0lAqA0OuKBLBvp423HPWQcCbhZz3JgyfIewsEz2f8U+X75xNIFHdiXZm2w==",
"dev": true,
"license": "MIT",
"dependencies": {
"vscode-jsonrpc": "9.0.2",
"vscode-languageserver-types": "3.18.3"
}
},
"node_modules/vscode-languageserver-textdocument": {
"version": "1.0.14",
"resolved": "https://registry.npmjs.org/vscode-languageserver-textdocument/-/vscode-languageserver-textdocument-1.0.14.tgz",
@@ -4829,6 +4851,13 @@
"dev": true,
"license": "MIT"
},
"node_modules/vscode-languageserver-types": {
"version": "3.18.3",
"resolved": "https://registry.npmjs.org/vscode-languageserver-types/-/vscode-languageserver-types-3.18.3.tgz",
"integrity": "sha512-XIlzJ7Qp/jzSI1ds7/FwPAWrPeTZA7pAtlW4hdJ1J6xXWJL6dR9QYnDhJOdLzdKhUQ5Mm6mvUMw+3DcOQQasPw==",
"dev": true,
"license": "MIT"
},
"node_modules/vscode-uri": {
"version": "3.2.0",
"resolved": "https://registry.npmjs.org/vscode-uri/-/vscode-uri-3.2.0.tgz",
package.json
+2 -1
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@@ -87,7 +87,8 @@
"oxlint": "^1.83.0",
"oxlint-tsgolint": "^7.0.2001",
"publint": "^0.3.24",
"typescript": "^7.0.2"
"typescript": "^7.0.2",
"vscode-languageserver-protocol": "^3.18.3"
},
"engines": {
"node": ">=26"
src/util/__tests__/lsp-completion.ts
+98 -199
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@@ -1,9 +1,25 @@
// oxlint-disable no-magic-numbers unicorn/no-null - tolerable here, this is a helper
import { spawn, type ChildProcessWithoutNullStreams } from "node:child_process";
import fs from "node:fs";
import path from "node:path";
import { setTimeout as delay } from "node:timers/promises";
import { pathToFileURL } from "node:url";
import {
type CompletionItem,
type CompletionList,
CompletionRequest,
ConfigurationRequest,
createMessageConnection,
DidOpenTextDocumentNotification,
InitializedNotification,
InitializeRequest,
type MessageConnection,
ShutdownRequest,
StreamMessageReader,
StreamMessageWriter,
} from "vscode-languageserver-protocol/node";
/**
* Print the completion labels TypeScript's language server offers at a marker
* inside a source file.
@@ -48,71 +64,18 @@ export interface CompletionResult {
readonly labels: readonly string[];
}
interface CompletionItem {
readonly label: string;
}
interface RpcMessage {
readonly id?: string | number;
readonly method?: string;
readonly params?: unknown;
readonly result?: unknown;
readonly error?: unknown;
}
interface Deferred {
readonly resolve: (message: RpcMessage) => void;
readonly reject: (error: Error) => void;
}
const isRecord = (value: unknown): value is Record<string, unknown> =>
typeof value === "object" && value !== null;
const isRpcMessage = (value: unknown): value is RpcMessage => {
if (!isRecord(value)) {
return false;
}
const { id, method } = value;
return (
(id === undefined ||
typeof id === "number" ||
typeof id === "string") &&
(method === undefined || typeof method === "string")
);
};
const isCompletionItem = (value: unknown): value is CompletionItem =>
isRecord(value) && typeof value["label"] === "string";
const serverRequestResult = (message: RpcMessage): readonly null[] | null => {
if (message.method !== "workspace/configuration") {
return null;
}
const items = isRecord(message.params)
? message.params["items"]
: undefined;
return Array.isArray(items) ? items.map(() => null) : [];
};
const completionLabels = (result: unknown): readonly string[] => {
if (!isRecord(result)) {
return [];
}
const { items } = result;
if (!Array.isArray(items)) {
const completionLabels = (
result: CompletionItem[] | CompletionList | null,
): readonly string[] => {
if (result === null) {
return [];
}
const items = Array.isArray(result) ? result : result.items;
return items
.filter(isCompletionItem)
.map((item) => item.label)
.toSorted((left, right) => left.localeCompare(right));
};
const frame = (message: object): string => {
const body = JSON.stringify(message);
return `Content-Length: ${Buffer.byteLength(body)}\r\n\r\n${body}`;
};
const markerPosition = (source: string, marker: string): Position => {
const index = source.indexOf(marker);
if (index === -1) {
@@ -124,153 +87,86 @@ const markerPosition = (source: string, marker: string): Position => {
return { line: lineIndex, character: line === undefined ? 0 : line.length };
};
/** Minimal JSON-RPC client for `tsc --lsp --stdio`. */
class LspClient {
readonly #child: ChildProcessWithoutNullStreams;
readonly #pending = new Map<string | number, Deferred>();
#buffer = Buffer.alloc(0);
#nextId = 1;
public constructor(repoRoot: string) {
this.#child = spawn(
path.join(repoRoot, "node_modules", ".bin", "tsc"),
["--lsp", "--stdio"],
{ cwd: repoRoot },
);
this.#child.stdout.on("data", (chunk: Buffer) => {
this.#consume(chunk);
});
this.#child.stderr.on("data", (chunk: Buffer) => {
process.stderr.write(chunk);
});
}
/** Send a request and settle when the server answers it. */
public request(method: string, params?: unknown): Promise<RpcMessage> {
const id = this.#nextId;
this.#nextId += 1;
const message = frame({ jsonrpc: "2.0", id, method, params });
return new Promise<RpcMessage>((resolve, reject) => {
this.#pending.set(id, { resolve, reject });
this.#child.stdin.write(message);
});
}
public notify(method: string, params: unknown): void {
this.#child.stdin.write(frame({ jsonrpc: "2.0", method, params }));
}
public dispose(): void {
this.#child.stdin.end();
this.#child.kill();
}
#consume(chunk: Buffer): void {
this.#buffer = Buffer.concat([this.#buffer, chunk]);
for (;;) {
const headerEnd = this.#buffer.indexOf("\r\n\r\n");
if (headerEnd === -1) {
return;
}
const header = this.#buffer.subarray(0, headerEnd).toString();
const match = /Content-Length: (\d+)/i.exec(header);
const lengthText = match === null ? undefined : match[1];
if (lengthText === undefined) {
return;
}
const bodyEnd = headerEnd + 4 + Number(lengthText);
if (this.#buffer.length < bodyEnd) {
return;
}
const body = this.#buffer
.subarray(headerEnd + 4, bodyEnd)
.toString();
this.#buffer = this.#buffer.subarray(bodyEnd);
const parsed: unknown = JSON.parse(body);
if (isRpcMessage(parsed)) {
this.#handle(parsed);
}
}
}
#handle(message: RpcMessage): void {
// Server -> client request: answer so the server does not stall.
if (message.method !== undefined && message.id !== undefined) {
this.#child.stdin.write(
frame({
jsonrpc: "2.0",
id: message.id,
result: serverRequestResult(message),
}),
);
return;
}
// Response to one of our requests.
const { id } = message;
if (id === undefined) {
return;
}
const deferred = this.#pending.get(id);
if (deferred === undefined) {
return;
}
this.#pending.delete(id);
if (message.error === undefined) {
deferred.resolve(message);
} else {
deferred.reject(new Error(JSON.stringify(message.error)));
}
}
}
/**
* One language server, initialized on first use, shared across probes. Callers
* own the lifecycle and must `close()` it.
*/
export class LspSession {
readonly #client: LspClient;
readonly #child: ChildProcessWithoutNullStreams;
readonly #connection: MessageConnection;
readonly #repoRoot: string;
#ready: Promise<void> | undefined;
public constructor(repoRoot: string) {
this.#repoRoot = repoRoot;
this.#client = new LspClient(repoRoot);
this.#child = spawn(
path.join(repoRoot, "node_modules", ".bin", "tsc"),
["--lsp", "--stdio"],
{ cwd: repoRoot },
);
this.#child.stderr.on("data", (chunk: Buffer) => {
process.stderr.write(chunk);
});
this.#connection = createMessageConnection(
new StreamMessageReader(this.#child.stdout),
new StreamMessageWriter(this.#child.stdin),
);
// Server -> client requests the server waits on: answer so it proceeds.
// `workspace/configuration` wants one reply per requested item; a
// catch-all covers the rest (e.g. `client/registerCapability`).
this.#connection.onRequest(ConfigurationRequest.type, ({ items }) =>
items.map(() => null),
);
this.#connection.onRequest(() => null);
this.#connection.listen();
}
public completionLabelsAt(
target: CompletionTarget,
): Promise<CompletionResult> {
return this.#ensureInitialized().then(() => {
const { uri, position } = this.#open(target);
return this.#client
.request("textDocument/completion", {
textDocument: { uri },
position,
context: { triggerKind: 1 },
})
.then((response) => ({
position,
labels: completionLabels(response.result),
}));
});
return this.#ensureInitialized()
.then(() => this.#open(target))
.then(({ uri, position }) =>
this.#connection
.sendRequest(CompletionRequest.type, {
textDocument: { uri },
position,
context: { triggerKind: 1 },
})
.then((result) => ({
position,
labels: completionLabels(result),
})),
);
}
/** `shutdown` + `exit`, then kill the server; safe after a failed probe. */
/** `shutdown` + close stdin, then kill the server; safe after a failed probe. */
public close(): Promise<void> {
return this.#client
.request("shutdown")
.then(() => {
this.#client.notify("exit", null);
return delay(EXIT_DELAY_MS);
})
.finally(() => {
this.#client.dispose();
});
return (
this.#connection
.sendRequest(ShutdownRequest.type)
// The TS 7 Go server logs a bare `context canceled` to stderr
// when it handles `exit`; EOF on stdin shuts it down cleanly
// (exit 0, no output) instead.
.then(() => {
this.#child.stdin.end();
})
.then(() => delay(EXIT_DELAY_MS))
.finally(() => {
this.#connection.dispose();
this.#child.kill();
})
);
}
#ensureInitialized(): Promise<void> {
this.#ready ??= this.#client
.request("initialize", {
this.#ready ??= this.#initialize();
return this.#ready;
}
#initialize(): Promise<void> {
return this.#connection
.sendRequest(InitializeRequest.type, {
processId: process.pid,
rootUri: pathToFileURL(this.#repoRoot).href,
workspaceFolders: [
@@ -285,16 +181,18 @@ export class LspSession {
},
},
})
.then(() => {
this.#client.notify("initialized", {});
});
return this.#ready;
.then(() =>
this.#connection.sendNotification(
InitializedNotification.type,
{},
),
);
}
#open(target: CompletionTarget): {
#open(target: CompletionTarget): Promise<{
readonly uri: string;
readonly position: Position;
} {
}> {
const absolute = path.resolve(this.#repoRoot, target.file);
const marker = target.marker ?? DEFAULT_MARKER;
const position = markerPosition(target.source, marker);
@@ -302,15 +200,16 @@ export class LspSession {
const uri = pathToFileURL(absolute).href;
// The server handles `didOpen` in order before the completion request,
// so no settle delay is needed.
this.#client.notify("textDocument/didOpen", {
textDocument: {
uri,
languageId: "typescript",
version: 1,
text,
},
});
return { uri, position };
return this.#connection
.sendNotification(DidOpenTextDocumentNotification.type, {
textDocument: {
uri,
languageId: "typescript",
version: 1,
text,
},
})
.then(() => ({ uri, position }));
}
}