languageserver: add .js extensions to imports (ESM prep) (#259)

docs/esm-migration-plan.md

@@ -4,6 +4,27 @@
 
 This document outlines the plan to migrate from TypeScript's deprecated `"moduleResolution": "node"` (node10) to `"moduleResolution": "node16"` or `"nodenext"`. This change is necessary because the published ESM packages have extensionless imports that don't work correctly in modern ESM environments.
 
+## TL;DR - Remaining Work
+
+- [x] expressions - Migrated ✅
+- [x] workflow-parser - Migrated ✅
+- [x] languageservice - Migrated ✅
+- [x] languageserver - Add `.js` extensions to imports ✅
+- [ ] languageserver - Update `tsconfig.build.json` to `moduleResolution: "node16"` (blocked by vscode-languageserver)
+- [ ] languageserver - Upgrade `vscode-languageserver` to stable v10+ when released
+
+**Blocker:** `vscode-languageserver@8.0.2` lacks ESM exports. Stable v10 with `exports` field needed.
+
+### ⚠️ Important: `skipLibCheck: true` Required
+
+All migrated packages use `skipLibCheck: true` in their `tsconfig.build.json`. This works around a TS2386 "Overload signatures must all be optional or required" error in `@types/node/module.d.ts`.
+
+**Why can't we just fix the error?** The error is in `@types/node`, a third-party package maintained by DefinitelyTyped. We can't modify `node_modules`, and upstream fixes take time.
+
+**Is `skipLibCheck` safe?** Yes. It only skips type checking of `.d.ts` files (declaration files from dependencies). Our own `.ts` source files are still fully type-checked. This is a common and recommended workaround for issues in third-party type definitions.
+
+---
+
 ## Issues Fixed
 
 This migration will resolve the following issues:
@@ -199,14 +220,13 @@ src/connection.ts(1,43): error TS2307: Cannot find module 'vscode-languageserver
 
 With `moduleResolution: "node16"`, TypeScript follows Node.js ESM resolution rules which require explicit `exports` for subpath imports like `vscode-languageserver/browser` and `vscode-languageserver/node`.
 
-**Status:** Verified December 2025. Version 9.0.1 is available but ESM export support is not confirmed.
+**Status:** Partial - `.js` extensions added, waiting for stable `vscode-languageserver` release with ESM exports to complete migration.
 
-**Current Decision:** The languageserver package is **deferred** from this migration until the upstream `vscode-languageserver` package adds proper ESM exports. It will continue using the old `moduleResolution: "node"` configuration.
+**Completed:** All relative imports in languageserver source files have been updated to use `.js` extensions. This is compatible with the current `moduleResolution: "node"` and will enable a seamless migration once a stable vscode-languageserver version with ESM exports is available.
 
 **Options to resolve:**
-- Wait for vscode-languageserver to add ESM exports
-- Try upgrading to vscode-languageserver v9.x to see if exports were added
-- Use a bundler to work around the module resolution
+- Wait for stable vscode-languageserver v10+ with ESM exports
+- Use pre-release `vscode-languageserver@10.0.0-next.16` (has proper exports but is unstable)
 - Fork or patch the dependency
 
 ---
@@ -218,7 +238,7 @@ With `moduleResolution: "node16"`, TypeScript follows Node.js ESM resolution rul
 | expressions | 1068 | ✅ Migrated |
 | workflow-parser | 292 | ✅ Migrated |
 | languageservice | 452 | ✅ Migrated |
-| languageserver | 6 files | ⏸️ Deferred (vscode-languageserver lacks ESM exports) |
+| languageserver | 31 | 🔶 Partial (`.js` extensions added, awaiting stable vscode-languageserver) |
 
 ---
 

languageserver/src/connection.ts

@@ -20,18 +20,18 @@ import {
   TextDocumentSyncKind
 } from "vscode-languageserver";
 import {TextDocument} from "vscode-languageserver-textdocument";
-import {getClient} from "./client";
-import {Commands} from "./commands";
-import {contextProviders} from "./context-providers";
-import {descriptionProvider} from "./description-provider";
-import {getFileProvider} from "./file-provider";
-import {InitializationOptions, RepositoryContext} from "./initializationOptions";
-import {onCompletion} from "./on-completion";
-import {ReadFileRequest, Requests} from "./request";
-import {getActionsMetadataProvider} from "./utils/action-metadata";
-import {TTLCache} from "./utils/cache";
-import {timeOperation} from "./utils/timer";
-import {valueProviders} from "./value-providers";
+import {getClient} from "./client.js";
+import {Commands} from "./commands.js";
+import {contextProviders} from "./context-providers.js";
+import {descriptionProvider} from "./description-provider.js";
+import {getFileProvider} from "./file-provider.js";
+import {InitializationOptions, RepositoryContext} from "./initializationOptions.js";
+import {onCompletion} from "./on-completion.js";
+import {ReadFileRequest, Requests} from "./request.js";
+import {getActionsMetadataProvider} from "./utils/action-metadata.js";
+import {TTLCache} from "./utils/cache.js";
+import {timeOperation} from "./utils/timer.js";
+import {valueProviders} from "./value-providers.js";
 
 export function initConnection(connection: Connection) {
   const documents: TextDocuments<TextDocument> = new TextDocuments(TextDocument);

languageserver/src/context-providers.test.ts

@@ -1,9 +1,9 @@
 import {data, DescriptionDictionary} from "@actions/expressions";
 import {WorkflowContext} from "@actions/languageservice/context/workflow-context";
 import {Mode} from "@actions/languageservice/context-providers/default";
-import {contextProviders} from "./context-providers";
-import {RepositoryContext} from "./initializationOptions";
-import {TTLCache} from "./utils/cache";
+import {contextProviders} from "./context-providers.js";
+import {RepositoryContext} from "./initializationOptions.js";
+import {TTLCache} from "./utils/cache.js";
 
 describe("contextProviders", () => {
   const mockCache = new TTLCache();

languageserver/src/context-providers.ts

@@ -3,11 +3,11 @@ import {ContextProviderConfig} from "@actions/languageservice";
 import {Mode} from "@actions/languageservice/context-providers/default";
 import {WorkflowContext} from "@actions/languageservice/context/workflow-context";
 import {Octokit} from "@octokit/rest";
-import {getSecrets} from "./context-providers/secrets";
-import {getStepsContext} from "./context-providers/steps";
-import {getVariables} from "./context-providers/variables";
-import {RepositoryContext} from "./initializationOptions";
-import {TTLCache} from "./utils/cache";
+import {getSecrets} from "./context-providers/secrets.js";
+import {getStepsContext} from "./context-providers/steps.js";
+import {getVariables} from "./context-providers/variables.js";
+import {RepositoryContext} from "./initializationOptions.js";
+import {TTLCache} from "./utils/cache.js";
 
 export function contextProviders(
   client: Octokit | undefined,

languageserver/src/context-providers/action-outputs.ts

@@ -1,7 +1,7 @@
 import {ActionOutputs, ActionReference} from "@actions/languageservice/action";
 import {Octokit} from "@octokit/rest";
-import {fetchActionMetadata} from "../utils/action-metadata";
-import {TTLCache} from "../utils/cache";
+import {fetchActionMetadata} from "../utils/action-metadata.js";
+import {TTLCache} from "../utils/cache.js";
 
 export async function getActionOutputs(
   octokit: Octokit,

languageserver/src/context-providers/secrets.ts

@@ -6,10 +6,10 @@ import {warn} from "@actions/languageservice/log";
 import {isMapping, isString} from "@actions/workflow-parser";
 import {Octokit} from "@octokit/rest";
 
-import {RepositoryContext} from "../initializationOptions";
-import {TTLCache} from "../utils/cache";
-import {errorStatus} from "../utils/error";
-import {getRepoPermission} from "../utils/repo-permission";
+import {RepositoryContext} from "../initializationOptions.js";
+import {TTLCache} from "../utils/cache.js";
+import {errorStatus} from "../utils/error.js";
+import {getRepoPermission} from "../utils/repo-permission.js";
 
 export async function getSecrets(
   workflowContext: WorkflowContext,

languageserver/src/context-providers/steps.test.ts

@@ -3,9 +3,9 @@ import {getStepsContext as getDefaultStepsContext} from "@actions/languageservic
 import {Octokit} from "@octokit/rest";
 import fetchMock from "fetch-mock";
 
-import {createWorkflowContext} from "../test-utils/workflow-context";
-import {TTLCache} from "../utils/cache";
-import {getStepsContext} from "./steps";
+import {createWorkflowContext} from "../test-utils/workflow-context.js";
+import {TTLCache} from "../utils/cache.js";
+import {getStepsContext} from "./steps.js";
 
 const workflow = `
 name: Caching Primes

languageserver/src/context-providers/steps.ts

@@ -3,8 +3,8 @@ import {parseActionReference} from "@actions/languageservice/action";
 import {WorkflowContext} from "@actions/languageservice/context/workflow-context";
 import {isActionStep} from "@actions/workflow-parser/model/type-guards";
 import {Octokit} from "@octokit/rest";
-import {TTLCache} from "../utils/cache";
-import {getActionOutputs} from "./action-outputs";
+import {TTLCache} from "../utils/cache.js";
+import {getActionOutputs} from "./action-outputs.js";
 
 export async function getStepsContext(
   octokit: Octokit,

languageserver/src/context-providers/variables.ts

@@ -7,10 +7,10 @@ import {isMapping, isString} from "@actions/workflow-parser";
 import {Octokit} from "@octokit/rest";
 import {RequestError} from "@octokit/request-error";
 
-import {RepositoryContext} from "../initializationOptions";
-import {TTLCache} from "../utils/cache";
-import {errorStatus} from "../utils/error";
-import {getRepoPermission} from "../utils/repo-permission";
+import {RepositoryContext} from "../initializationOptions.js";
+import {TTLCache} from "../utils/cache.js";
+import {errorStatus} from "../utils/error.js";
+import {getRepoPermission} from "../utils/repo-permission.js";
 
 export async function getVariables(
   workflowContext: WorkflowContext,

languageserver/src/description-provider.ts

@@ -1,8 +1,8 @@
 import {DescriptionProvider} from "@actions/languageservice/hover";
 import {Octokit} from "@octokit/rest";
-import {getActionDescription} from "./description-providers/action-description";
-import {getActionInputDescription} from "./description-providers/action-input";
-import {TTLCache} from "./utils/cache";
+import {getActionDescription} from "./description-providers/action-description.js";
+import {getActionInputDescription} from "./description-providers/action-input.js";
+import {TTLCache} from "./utils/cache.js";
 
 export function descriptionProvider(client: Octokit | undefined, cache: TTLCache): DescriptionProvider {
   const getDescription: DescriptionProvider["getDescription"] = async (context, token, path) => {

languageserver/src/description-providers/action-description.test.ts

@@ -1,9 +1,9 @@
 import {Octokit} from "@octokit/rest";
 import fetchMock from "fetch-mock";
-import {createWorkflowContext} from "../test-utils/workflow-context";
-import {TTLCache} from "../utils/cache";
-import {getActionDescription} from "./action-description";
-import {actionsCheckoutMetadata} from "../test-utils/action-metadata";
+import {createWorkflowContext} from "../test-utils/workflow-context.js";
+import {TTLCache} from "../utils/cache.js";
+import {getActionDescription} from "./action-description.js";
+import {actionsCheckoutMetadata} from "../test-utils/action-metadata.js";
 
 const workflow = `
 name: Hello World

languageserver/src/description-providers/action-description.ts

@@ -2,8 +2,8 @@ import {actionUrl, parseActionReference} from "@actions/languageservice/action";
 import {isActionStep} from "@actions/workflow-parser/model/type-guards";
 import {Step} from "@actions/workflow-parser/model/workflow-template";
 import {Octokit} from "@octokit/rest";
-import {fetchActionMetadata} from "../utils/action-metadata";
-import {TTLCache} from "../utils/cache";
+import {fetchActionMetadata} from "../utils/action-metadata.js";
+import {TTLCache} from "../utils/cache.js";
 
 export async function getActionDescription(client: Octokit, cache: TTLCache, step: Step): Promise<string | undefined> {
   if (!isActionStep(step)) {

languageserver/src/description-providers/action-input.test.ts

@@ -2,10 +2,10 @@ import {StringToken} from "@actions/workflow-parser/templates/tokens/string-toke
 import {Octokit} from "@octokit/rest";
 import fetchMock from "fetch-mock";
 
-import {actionsCheckoutMetadata} from "../test-utils/action-metadata";
-import {createWorkflowContext} from "../test-utils/workflow-context";
-import {TTLCache} from "../utils/cache";
-import {getActionInputDescription} from "./action-input";
+import {actionsCheckoutMetadata} from "../test-utils/action-metadata.js";
+import {createWorkflowContext} from "../test-utils/workflow-context.js";
+import {TTLCache} from "../utils/cache.js";
+import {getActionInputDescription} from "./action-input.js";
 
 const workflow = `
 name: Hello World

languageserver/src/description-providers/action-input.ts

@@ -4,8 +4,8 @@ import {isActionStep} from "@actions/workflow-parser/model/type-guards";
 import {Step} from "@actions/workflow-parser/model/workflow-template";
 import {TemplateToken} from "@actions/workflow-parser/templates/tokens/template-token";
 import {Octokit} from "@octokit/rest";
-import {fetchActionMetadata} from "../utils/action-metadata";
-import {TTLCache} from "../utils/cache";
+import {fetchActionMetadata} from "../utils/action-metadata.js";
+import {TTLCache} from "../utils/cache.js";
 
 export async function getActionInputDescription(
   client: Octokit,

languageserver/src/file-provider.ts

@@ -2,7 +2,7 @@ import {File} from "@actions/workflow-parser/workflows/file";
 import {FileProvider} from "@actions/workflow-parser/workflows/file-provider";
 import {fileIdentifier} from "@actions/workflow-parser/workflows/file-reference";
 import {Octokit} from "@octokit/rest";
-import {TTLCache} from "./utils/cache";
+import {TTLCache} from "./utils/cache.js";
 import * as vscodeURI from "vscode-uri";
 
 export function getFileProvider(

languageserver/src/index.ts

@@ -6,7 +6,7 @@ import {
 } from "vscode-languageserver/browser";
 import {createConnection as createNodeConnection} from "vscode-languageserver/node";
 
-import {initConnection} from "./connection";
+import {initConnection} from "./connection.js";
 
 /** Helper function determining whether we are executing with node runtime */
 function isNode(): boolean {

languageserver/src/on-completion.ts

@@ -2,12 +2,12 @@ import {complete} from "@actions/languageservice/complete";
 import {Octokit} from "@octokit/rest";
 import {CompletionItem, Connection, Position} from "vscode-languageserver";
 import {TextDocument} from "vscode-languageserver-textdocument";
-import {contextProviders} from "./context-providers";
-import {getFileProvider} from "./file-provider";
-import {RepositoryContext} from "./initializationOptions";
-import {Requests} from "./request";
-import {TTLCache} from "./utils/cache";
-import {valueProviders} from "./value-providers";
+import {contextProviders} from "./context-providers.js";
+import {getFileProvider} from "./file-provider.js";
+import {RepositoryContext} from "./initializationOptions.js";
+import {Requests} from "./request.js";
+import {TTLCache} from "./utils/cache.js";
+import {valueProviders} from "./value-providers.js";
 
 export async function onCompletion(
   connection: Connection,

languageserver/src/utils/action-metadata.test.ts

@@ -1,7 +1,7 @@
 import {Octokit} from "@octokit/rest";
 import fetchMock from "fetch-mock";
-import {fetchActionMetadata} from "./action-metadata";
-import {TTLCache} from "./cache";
+import {fetchActionMetadata} from "./action-metadata.js";
+import {TTLCache} from "./cache.js";
 
 // A simplified version of the action.yml file from actions/checkout
 const actionMetadataContent = `

languageserver/src/utils/action-metadata.ts

@@ -3,8 +3,8 @@ import {ActionsMetadataProvider} from "@actions/languageservice";
 import {error} from "@actions/languageservice/log";
 import {Octokit, RestEndpointMethodTypes} from "@octokit/rest";
 import {parse} from "yaml";
-import {TTLCache} from "./cache";
-import {errorMessage, errorStatus} from "./error";
+import {TTLCache} from "./cache.js";
+import {errorMessage, errorStatus} from "./error.js";
 
 export function getActionsMetadataProvider(
   client: Octokit | undefined,

languageserver/src/utils/repo-permission.ts

@@ -1,9 +1,9 @@
 import {error} from "@actions/languageservice/log";
 import {Octokit} from "@octokit/rest";
-import {RepositoryContext} from "../initializationOptions";
-import {TTLCache} from "./cache";
-import {errorStatus} from "./error";
-import {getUsername} from "./username";
+import {RepositoryContext} from "../initializationOptions.js";
+import {TTLCache} from "./cache.js";
+import {errorStatus} from "./error.js";
+import {getUsername} from "./username.js";
 
 export type RepoPermission = "admin" | "write" | "read" | "none";
 

languageserver/src/utils/username.ts

@@ -1,5 +1,5 @@
 import {Octokit} from "@octokit/rest";
-import {TTLCache} from "./cache";
+import {TTLCache} from "./cache.js";
 
 export async function getUsername(octokit: Octokit, cache: TTLCache): Promise<string> {
   return await cache.get(`/username`, undefined, () => fetchUsername(octokit));

languageserver/src/value-providers.ts

@@ -2,11 +2,11 @@ import {ValueProviderConfig} from "@actions/languageservice";
 import {WorkflowContext} from "@actions/languageservice/context/workflow-context";
 import {ValueProviderKind} from "@actions/languageservice/value-providers/config";
 import {Octokit} from "@octokit/rest";
-import {RepositoryContext} from "./initializationOptions";
-import {TTLCache} from "./utils/cache";
-import {getActionInputValues} from "./value-providers/action-inputs";
-import {getEnvironments} from "./value-providers/job-environment";
-import {getRunnerLabels} from "./value-providers/runs-on";
+import {RepositoryContext} from "./initializationOptions.js";
+import {TTLCache} from "./utils/cache.js";
+import {getActionInputValues} from "./value-providers/action-inputs.js";
+import {getEnvironments} from "./value-providers/job-environment.js";
+import {getRunnerLabels} from "./value-providers/runs-on.js";
 
 export function valueProviders(
   client: Octokit | undefined,

languageserver/src/value-providers/action-inputs.ts

@@ -3,8 +3,8 @@ import {WorkflowContext} from "@actions/languageservice/context/workflow-context
 import {Value} from "@actions/languageservice/value-providers/config";
 import {isActionStep} from "@actions/workflow-parser/model/type-guards";
 import {Octokit} from "@octokit/rest";
-import {fetchActionMetadata} from "../utils/action-metadata";
-import {TTLCache} from "../utils/cache";
+import {fetchActionMetadata} from "../utils/action-metadata.js";
+import {TTLCache} from "../utils/cache.js";
 
 export async function getActionInputs(
   client: Octokit,

languageserver/src/value-providers/job-environment.ts

@@ -1,6 +1,6 @@
 import {Value} from "@actions/languageservice/value-providers/config";
 import {Octokit} from "@octokit/rest";
-import {TTLCache} from "../utils/cache";
+import {TTLCache} from "../utils/cache.js";
 
 export async function getEnvironments(client: Octokit, cache: TTLCache, owner: string, name: string): Promise<Value[]> {
   const environments = await cache.get(`${owner}/${name}/environments`, undefined, () =>

languageserver/src/value-providers/runs-on.ts

@@ -2,8 +2,8 @@ import {log} from "@actions/languageservice/log";
 import {Value} from "@actions/languageservice/value-providers/config";
 import {DEFAULT_RUNNER_LABELS} from "@actions/languageservice/value-providers/default";
 import {Octokit} from "@octokit/rest";
-import {TTLCache} from "../utils/cache";
-import {errorMessage} from "../utils/error";
+import {TTLCache} from "../utils/cache.js";
+import {errorMessage} from "../utils/error.js";
 
 // Limitation: getRunnerLabels returns default hosted labels and labels for repository self-hosted runners.
 // It doesn't return labels for organization runners visible to the repository.

languageserver/tsconfig.build.json

@@ -5,6 +5,7 @@
     "declaration": true,
     "declarationMap": true,
     "noEmit": false,
-    "outDir": "./dist"
+    "outDir": "./dist",
+    "skipLibCheck": true
   }
 }