feat: support pull diagnostics in the LSP client (C#, Kotlin, etc)

[Hona]

TL;DR

1. Dev (no errors showing)
   Our client only spoke push diagnostics.
   Roslyn doesn't push for C# - it registers pull providers and waits to be asked.
   So after an edit we waited 3s for a push that never came and surfaced nothing.

2. Earlier branch (~4s)
   Added pull diagnostics but wrapped in smart "waiting/settling/convergence" policy and a Roslyn-specific compiler-category branch.
   It worked, but the extra policy/sweeps added ~3-4s of latency even on warm files, and some cases hit a 10s pull timeout.

3. New branch (near instant)
   Generic pull-aware client, no server-specific branches, no settle timers.
   After didOpen/didChange we issue current-document pulls in parallel for every registered identifier and return on the first match.
   Warm C# edit in the UpBlazor repro: about 0.7s and returns the 3 CS0103 errors.

fixes #3116 and ...?

C#, Kotlin etc work great now

many LSPs only do pulled diagnostics, and dev used to do push only

[Copilot]

Pull request overview

Updates the LSP client to respect servers that advertise incremental text sync, and extends the fake LSP fixture + tests to verify the new didChange behavior.

Changes:

• Send ranged textDocument/didChange notifications when the server advertises textDocumentSync.change = 2 (incremental sync).
• Extend the fake LSP server to advertise incremental sync and capture the last didChange payload for assertions.
• Add a regression test asserting ranged didChange content for incremental-sync servers.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
packages/opencode/src/lsp/client.ts	Determine sync kind from server capabilities and send ranged didChange for incremental sync; adds diagnostics polling/request infrastructure used by waitForDiagnostics.
packages/opencode/test/fixture/lsp/fake-lsp-server.js	Advertises incremental sync and records/returns the last textDocument/didChange params for tests.
packages/opencode/test/lsp/client.test.ts	Adds test validating ranged didChange payload for incremental sync servers using the fake server.

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

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[Copilot]

Pull request overview

Copilot reviewed 12 out of 12 changed files in this pull request and generated 6 comments.

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[Copilot]

waitForDocumentDiagnostics only retries pulls when a new diagnostic registration arrives (next !== "registration" returns). If the server supports pull but the first pull times out/returns empty while the server is still computing, and it doesn’t change registrations or push diagnostics, this will exit early (on push timeout) without retrying within the overall 5s window. Consider polling/retrying pull requests (with a small backoff) until the overall timeout elapses.

[Copilot]

waitForFullDiagnostics has the same early-exit behavior: after one pull sweep it returns unless registrations change. For pull-only servers that take longer than DIAGNOSTICS_REQUEST_TIMEOUT_MS (3s) to compute, this can cause waitForDiagnostics to return before the overall 10s timeout without ever seeing diagnostics. Consider retrying pull requests until the full timeout expires (or until a push arrives).

Suggested change

	const next = await Promise.race([
	pushWait.then((ready) => (ready ? "push" : "timeout" as const)),
	waitForRegistrationChange(remaining).then((changed) => (changed ? "registration" : "timeout" as const)),
	])
	if (next !== "registration") return
	const retryDelay = Math.min(DIAGNOSTICS_DEBOUNCE_MS, remaining)
	const next = await Promise.race([
	pushWait.then((ready) => (ready ? "push" : "timeout" as const)),
	waitForRegistrationChange(remaining).then((changed) => (changed ? "registration" : "timeout" as const)),
	new Promise<"retry">((resolve) => setTimeout(() => resolve("retry"), retryDelay)),
	])
	if (next === "push" || next === "timeout") return

[Copilot]

The client advertises workspace.diagnostics.refreshSupport: true but the workspace/diagnostic/refresh handler currently just returns null and doesn't trigger any re-pull. Per the LSP diagnostics spec, receiving this request should cause the client to re-request diagnostics (at least for currently-open documents), otherwise servers that rely on refresh will never update pull diagnostics.

Suggested change

	connection.onRequest("workspace/workspaceFolders", async () => [
	{
	name: "workspace",
	uri: pathToFileURL(input.root).href,
	},
	])
	connection.onRequest("workspace/diagnostic/refresh", async () => null)
	const applyPulledDiagnostics = (
	filePath: string,
	report:
	| {
	kind?: "full" | "unchanged"
	items?: VSCodeDiagnostic[]
	relatedDocuments?: Record<
	string,
	{
	kind?: "full" | "unchanged"
	items?: VSCodeDiagnostic[]
	}
	>
	}
	| null
	| undefined,
	) => {
	if (!report) return
	const previous = published.get(filePath)
	published.set(filePath, {
	at: Date.now(),
	version: previous?.version,
	})
	if (report.kind !== "unchanged" && Array.isArray(report.items)) {
	updatePushDiagnostics(filePath, report.items)
	}
	for (const [uri, relatedReport] of Object.entries(report.relatedDocuments ?? {})) {
	const relatedPath = getFilePath(uri)
	if (!relatedPath) continue
	const relatedPrevious = published.get(relatedPath)
	published.set(relatedPath, {
	at: Date.now(),
	version: relatedPrevious?.version,
	})
	if (relatedReport.kind !== "unchanged" && Array.isArray(relatedReport.items)) {
	updatePushDiagnostics(relatedPath, relatedReport.items)
	}
	}
	}
	connection.onRequest("workspace/workspaceFolders", async () => [
	{
	name: "workspace",
	uri: pathToFileURL(input.root).href,
	},
	])
	connection.onRequest("workspace/diagnostic/refresh", async () => {
	l.info("workspace/diagnostic/refresh")
	const trackedFilePaths = new Set([...published.keys(), ...pushDiagnostics.keys()])
	await Promise.allSettled(
	[...trackedFilePaths].map(async (filePath) => {
	try {
	const report = await connection.sendRequest<{
	kind?: "full" | "unchanged"
	items?: VSCodeDiagnostic[]
	relatedDocuments?: Record<
	string,
	{
	kind?: "full" | "unchanged"
	items?: VSCodeDiagnostic[]
	}
	>
	}>("textDocument/diagnostic", {
	textDocument: {
	uri: pathToFileURL(filePath).href,
	},
	})
	applyPulledDiagnostics(filePath, report)
	} catch (error) {
	l.warn("workspace/diagnostic/refresh failed", {
	path: filePath,
	error,
	})
	}
	}),
	)
	return null
	})

[Copilot]

requestWorkspaceDiagnosticReport treats the request as handled only when byFile.size > 0. A successful workspace/diagnostic response with zero items (meaning “no workspace diagnostics”) would be considered unhandled, which can unnecessarily extend waits and can leave stale workspace pull diagnostics around. Consider setting handled based on receiving a valid report (e.g., Array.isArray(report.items)), not on whether any diagnostics were returned.

[Copilot]

Npm.which(pkg, bin) checks files.includes(bin) for an exact match. On Windows, npm/bun typically creates shims like pyright-langserver.cmd (and/or .ps1) in node_modules/.bin, so this exact-match check can return none even though the requested bin exists. Consider matching against PATHEXT variants (or doing a prefix match + extension handling) so callers can pass the logical bin name and still resolve correctly cross-platform.

[Copilot]

The TypeScript special-case stores the first publishDiagnostics into pushDiagnostics but returns without calling updatePushDiagnostics, so no Event.Diagnostics is published. waitForFreshPush() relies on that bus event to re-check published, which means waitForDiagnostics() can unnecessarily block until timeout even though diagnostics have already arrived. Consider still publishing the event (or remove this special-case and rely on debounce/version checks instead).

Suggested change

	pushDiagnostics.set(filePath, params.diagnostics)
	updatePushDiagnostics(filePath, params.diagnostics)

[lowlyocean]

After checking out this branch, I'm having trouble getting bun dev debug lsp diagnostics </path/to/file.kt> --print-logs --log-level DEBUG to show anything other than empty result {}. Is there something else needed besides having .config/opencode/opencode.json have a top-level "lsp": true ?

[Hona]

@lowlyocean i assume you're running bun dev from the opencode repo - and passing an absolute path to the file?
it kinda needs the cwd to be the kotlin dir to spawn and etc

[Hona]

e.g. bun dev debug lsp diagnostics "C:\Repos\kotlin-real-smoke-ktor\src\main\kotlin\com\example\LspProbe.kt" --print-logs --log-level DEBUG

will return nothing

i have a pwsh wrapper that does this correctly, e.g.

ocl -- debug lsp diagnostics "src/main/kotlin/com/example/LspProbe.kt" --print-logs --log-level DEBUG does work

e.g. here's what that looks like:

function opencode-local {
  $ArgumentList = @($args)
  $repo = "C:/Repos/sst/opencode/packages/opencode"
  if ($ArgumentList.Count -gt 0 -and $ArgumentList[0] -eq '--') {
    $ArgumentList = @($ArgumentList | Select-Object -Skip 1)
  }
  $entryPath = Join-Path $repo 'src/index.ts'
  $entryUri = [System.Uri]::new($entryPath).AbsoluteUri
  $cwd = $PWD.ProviderPath
  $script = @"
const cwd = $($cwd | ConvertTo-Json -Compress)
process.chdir(cwd)
process.env.PWD = cwd
process.argv = ['bun', $($entryPath | ConvertTo-Json -Compress), ...process.argv.slice(1)]
await import($($entryUri | ConvertTo-Json -Compress))
"@
  & bun --cwd $repo --conditions=browser -e $script -- @ArgumentList
}
Set-Alias ocl opencode-local

[lowlyocean]

Thanks - still no luck, I tried converting to bash,

opencode-local() {
  local repo="~/.local/bin/opencode/packages/opencode"
  local entryPath="$repo/src/index.ts"

  # Handle '--' argument if it's the first one
  if [[ "$1" == '--' ]]; then
    shift
  fi

  # Generate URI and JSON strings using bun (since bun is required anyway)
  # This replaces PowerShell's [System.Uri] and ConvertTo-Json
  local entryUri
  entryUri=$(bun -e "console.log(require('url').pathToFileURL('$entryPath').href)" 2>/dev/null)

  local cwdJson
  cwdJson=$(bun -e "console.log(JSON.stringify('$(pwd)'))" 2>/dev/null)

  local entryPathJson
  entryPathJson=$(bun -e "console.log(JSON.stringify('$entryPath'))" 2>/dev/null)

  local entryUriJson
  entryUriJson=$(bun -e "console.log(JSON.stringify('$entryUri'))" 2>/dev/null)

  # Construct the script
  local script="
const cwd = $cwdJson
process.chdir(cwd)
process.env.PWD = cwd
process.argv = ['bun', $entryPathJson, ...process.argv.slice(1)]
await import($entryUriJson)
"

  # Run bun with the script and arguments
  bun --cwd "$repo" --conditions=browser -e "$script" -- "$@"
}

alias ocl=opencode-local

And cwd when I run the ocl command is the directory where have the symlink defined for "kotlin-lsp"

My opencode.json:

  "lsp": {
    "kotlin-ls": {
      "disabled": true,
    },
    "kotlin-lsp": {
      "command": ["kotlin-lsp", "--stdio"],
      "extensions": [".kt", ".kts"]
    }
  }

[Hona]

@lowlyocean can you try with just "lsp": true - we use the official kotlin-lsp already so I'm not sure why we need the override?

[Hona]

I threw an agent at your script: