164 lines
8.5 KiB
Markdown
164 lines
8.5 KiB
Markdown
# LSP navigation
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The LSP seam — a [capability seam](../../.agents/notes/implemented/architecture/2026-07-15-lsp-capability-seam.md) exposing semantic code navigation on one `ctx.lsp` service, split across packages: interface ([dsh-lsp](../../packages/lsp/lsp), `ctx.lsp` + the provider registry), a generic implementation ([dsh-lsp-local](../../packages/lsp/lsp-local), a configured stdio language-server host), and consumer ([dsh-tool-lsp](../../packages/lsp/tool-lsp), the `lsp` tool schema). LSP is **one optional capability**, not part of the agent-loop spine — so its vocabulary lives here, not in [core.md](core.md). A provider swap does not change how the model asks for navigation.
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Source: [`packages/lsp/lsp/src/types.ts`](../../packages/lsp/lsp/src/types.ts)
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## Operations and coordinates
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The seam and model expose exactly four semantic queries; the union is closed, so adding one is a compile-enforced change across the seam, providers, and the tool. Positions and ranges are zero-based UTF-16, matching the protocol; the model-facing tool owns the one-based cursor convention and converts on the way in and out.
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```ts type-equiv
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/**
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* The four semantic queries the seam and model expose. A closed union: adding an operation is a
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* compile-enforced change across the seam, providers, and the tool. Symbols and call hierarchy are
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* deliberately deferred (they need different schemas).
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*/
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type LspOperation = 'goToDefinition' | 'findReferences' | 'goToImplementation' | 'hover'
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```
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```ts type-equiv
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/** A zero-based UTF-16 cursor coordinate, matching the LSP wire convention. */
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interface LspPosition {
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/** Zero-based line. */
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readonly line: number
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/** Zero-based UTF-16 code-unit offset within the line. */
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readonly character: number
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}
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```
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```ts type-equiv
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/** A zero-based UTF-16 half-open range `[start, end)`. */
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interface LspRange {
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readonly start: LspPosition
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readonly end: LspPosition
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}
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```
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## Request
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Every field is required: `workspaceRoot` is caller-supplied, `languageId` comes from the provider's registration (not the request), and consumers own timeouts and result limits — so no field needs implementation defaulting and there is no `resolve()` step. The provider receives the caller's request plus the derived `languageId`, which only synchronizes the transient document and never participates in selection.
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```ts type-equiv
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/**
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* A caller's normalized query. Every field is required: `workspaceRoot` is caller-supplied,
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* `languageId` comes from the provider registration (not here), and consumers own timeouts and
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* result limits — so no field needs implementation defaulting and there is no `resolve()` step.
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*/
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interface LspQueryRequest {
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/** Which semantic query to run. */
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readonly operation: LspOperation
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/** The source file to query (relative to `workspaceRoot` or absolute; the provider canonicalizes). */
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readonly filePath: string
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/** The zero-based UTF-16 cursor position to query at. */
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readonly position: LspPosition
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/** The workspace root the provider resolves against and indexes; required, never defaulted. */
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readonly workspaceRoot: string
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}
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```
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```ts type-equiv
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/**
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* A request as a provider receives it: the caller's {@link LspQueryRequest} plus the `languageId`
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* the seam derived from the provider's extension mapping. The language id only synchronizes the
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* transient document; it does not participate in selection.
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*/
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interface LspProviderQuery extends LspQueryRequest {
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/** The LSP language id for `filePath`, from this provider's extension mapping. */
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readonly languageId: string
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}
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```
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## Result
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A CLOSED discriminated union: navigation operations normalize to `locations`, `hover` to content or `null`. Consumers `switch` on `kind` to exhaustiveness so a new arm breaks compilation until handled. `findReferences` always includes declarations — the provider enforces this internally, so callers get no flag. The `locations` variant carries `resolvedWorkspaceRoot`: the provider's canonical form of the request's `workspaceRoot` and the root its `file:` URIs are relative to, so a caller relativizing display paths uses it rather than the possibly-symlinked request root.
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```ts type-equiv
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/** One resolved location: a document URI and the range within it. */
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interface LspLocation {
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/** The target document URI (`file:` or otherwise), verbatim from the server. */
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readonly uri: string
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/** The range within the target document. */
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readonly range: LspRange
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}
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```
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```ts type-equiv
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/** Normalized hover content, or `null` for no hover at the position. */
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interface LspHover {
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/** The normalized hover text (markdown or plaintext, provider-joined). */
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readonly contents: string
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/** The range the hover applies to, when the server supplied one. */
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readonly range?: LspRange
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}
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```
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```ts type-equiv
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/**
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* The closed result union. Navigation operations (`goToDefinition`, `findReferences`,
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* `goToImplementation`) normalize to `locations`; `hover` normalizes to content or `null`.
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* Consumers `switch` on `kind` to exhaustiveness so a new arm breaks compilation until handled.
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*
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* The `locations` variant carries `resolvedWorkspaceRoot`: the provider's canonical form of the
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* request's `workspaceRoot`, and the root its `file:` location URIs are relative to. A caller that
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* relativizes display paths MUST use this, not the request's (possibly symlinked) `workspaceRoot`;
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* otherwise a symlinked workspace misclassifies in-workspace results as external.
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*/
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type LspQueryResult =
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| { readonly kind: 'locations'; readonly locations: readonly LspLocation[]; readonly resolvedWorkspaceRoot: string }
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| { readonly kind: 'hover'; readonly hover: LspHover | null }
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```
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## Provider and service
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A provider owns a stable branded `id` and an exclusive lowercase leading-dot extension map. `registerProvider` reserves the id and every extension atomically — an invalid or conflicting registration publishes nothing — and its disposer releases all reservations. Selection is per query and order-independent; no match throws `LspError` `LSP_UNAVAILABLE`. The seam exposes no protocol types, process/document controls, or generic JSON-RPC escape hatch.
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```ts type-equiv
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/**
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* A language-server backend registered on `ctx.lsp`. Each provider owns a stable {@link
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* LspProviderId} and an extension-to-language-id map (lowercase, leading-dot keys).
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* `findReferences` always includes declarations — the provider enforces this internally; callers
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* get no flag.
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*/
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interface LspProvider {
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/** Stable provider identity, reserved atomically with the extension mappings. */
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readonly id: LspProviderId
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/** Lowercase leading-dot extension → LSP language id (e.g. `{ '.ts': 'typescript' }`). */
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readonly extensionToLanguage: Readonly<Record<string, string>>
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/**
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* Run one query. The seam has already selected this provider and derived `languageId`.
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* @param request - the resolved provider query (caller request + derived language id).
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* @param signal - optional cancellation; the provider stops its own work when it aborts.
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* @returns the normalized, closed-union result.
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*/
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query(request: LspProviderQuery, signal?: AbortSignal): Promise<LspQueryResult>
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}
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```
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```ts type-equiv
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/**
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* The LSP capability seam (`ctx.lsp`). Owns provider registration/selection and normalized query
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* execution; exposes exactly the four operations and no protocol escape hatch.
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*/
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interface LspService {
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/**
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* Register a provider, atomically reserving its id and every normalized extension. Any conflict
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* or invalid input publishes nothing and throws `LspError`; the returned disposer releases all
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* reservations. Disposed with the calling fiber.
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* @param provider - the backend to register.
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* @returns a synchronous disposer releasing the id and all extension reservations.
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*/
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registerProvider(provider: LspProvider): () => void
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/**
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* Select a provider by the file's extension and run one query. Selection is per-query and
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* order-independent; no match throws `LspError` `LSP_UNAVAILABLE`.
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* @param request - the normalized query.
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* @param signal - optional cancellation forwarded to the selected provider.
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* @returns the normalized, closed-union result.
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*/
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query(request: LspQueryRequest, signal?: AbortSignal): Promise<LspQueryResult>
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}
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```
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`LspProviderId` is the seam's branded id (`Branded<'LspProviderId'>` from [dsh-brand](../../packages/util/brand)); `LspError` extends `HarnessError` with stable codes such as `LSP_INVALID_PROVIDER`, `LSP_CONFLICT`, `LSP_UNAVAILABLE`, `LSP_DISPOSED`, `LSP_UNSUPPORTED_OPERATION`, and `LSP_MALFORMED_RESPONSE`, which callers route on instead of parsing `message`.
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