Commands to install/uninstall roslyn-language-server for the Copilot CLI by phil-allen-msft · Pull Request #9344 · dotnet/vscode-csharp

phil-allen-msft · 2026-05-22T17:08:40Z

2 new commands (invokable from Command Palette/F1) to install and uninstall, which is really are edits on $HOME/.copilot/lsp-config.json

Reasonable error handling and notifications are present. Initial integration with microsoft-tas-client as well.

To update the 'redist' copy of lsp-config.json which is merged in as part of install, run npm run ingest

Unittests added; manually tested with no file (file created, content added), existing file which is C# (no changes), and existing file which has C++-looking bindings (content added).

…bove fullConfig changes to the lsp-config.json file if it exists, and write a new lsp-config.json file if it doesn't exist, assuming the .copilot folder does exist.

…uded in the vsix. Copy the file from the dotnet/skills repo now.

… on the user's machine already contains content for the roslyn-language-server. If so, make no changes.

…yn-language-server for Copilot CLI' runs multiple times, the resulting lsp-config.json has exactly the same contents as the copy of the file shipped with the product initially.

…do the same copy that you did earlier of the lsp-config.json from the dotnet/skills repo, but do it again when 'npm run ingest' is specifically run.

…ain. Change the Roslyn detection logic such that if there is a lspServer.csharp object in the read lsp-config.json, that counts as Roslyn detection = true

…epo and in the eventual extension to be 'redist'. Update all references.

… should find the lsp-config.json in the customer's HOME/.copilot directory; if it exists it should parse the file, and if the "lspServers.csharp" element exists, remove the "lspServers.csharp" element and leave all others.

…aming for the uninstall command

…or an object named 'csharp', look for an object that lists ".cs" in the "fileExtensions" collection. Use lsp-config.json in the redist folder as a guide.

…search for content to delete by looking for an lspServer object that has a "fileExtensions" with ".cs"

…t into one method and use from both existing implementation sites. Change how the callers of getCSharpServerNames works so that 'contains Roslyn Language Server' need only find one instance before eventually returns true.

…origin/main such that if they contained #sym:RoslynLanguageServer , they instead contain CSharpLsp

Fix element 1 in the above list. (create .copilot file if necessary)

… from the package.json file Now remove the "dotnet.experiments.targetPopulation" property from package.json

Update message text to reflect current behavior

…not exist, it reports an error

jasonmalinowski · 2026-05-22T21:43:38Z

+        expect(finalContent).toBe(packagedContent);
+    });
+
+    test('does not modify config when any server maps .cs in fileExtensions', () => {


Is this the behavior we want? If somebody is wanting to run us to upgrade from some other LSP to our own, don't we want to remove the other one?

jasonmalinowski · 2026-05-22T21:46:41Z

+    await fs.mkdir(path.dirname(outputPath), { recursive: true });
+    await fs.writeFile(outputPath, content, 'utf8');
+    console.log(`Updated ${outputPath} from ${sourceUrl}`);


Is there not some other npm package for downloading to a file easily?

jasonmalinowski · 2026-05-22T21:48:19Z

    "createTags": "npx ts-node tasks/tags/createTags.ts",
    "fixLocUrls": "npx ts-node tasks/debugger/fixLocUrls.ts",
    "generateOptionsSchema": "npx ts-node tasks/debugger/generateOptionsSchema.ts",
+    "ingest": "npx ts-node tasks/components/ingestCopilotLspConfig.ts",


Is this something we expect is happening automatically during a build or something we need to do on a regular basis?

I don't think this should happen automatically on build - otherwise a build could randomly fail if the config changes.

jasonmalinowski · 2026-05-22T21:49:32Z

    );
+    context.subscriptions.push(
+        vscode.commands.registerCommand(installCopilotLspCommand, async () => {
+            const lspConfigPath = path.join(os.homedir(), '.copilot', 'lsp-config.json');


Rather than doing manual configuration this way, should we just be installing one of our existing plugins that contains the registration?

jasonmalinowski · 2026-05-22T21:51:17Z

+
+function containsCSharpServer(lspServers: { [key: string]: unknown }): boolean {
+    for (const [serverName, server] of Object.entries(lspServers)) {
+        if (serverName === 'csharp' || serverContainsCSharpFileExtension(server)) {


Why is this checking the sever name but the other function above is just looking for the extension?

Feels like they should both check for extension - I believe server name could be anything.

Also curious what happens if there is already a c# server configured that doesn't use roslyn-language-server.

I do also wonder if we could install the lsp config as a plugin (e.g. ship the plugin in the extension, then use CLI commands to install the plugin). And rely on the cli for de-dupe? Not sure if thats any better though

dibarbet · 2026-05-22T18:37:40Z

    );
+    context.subscriptions.push(
+        vscode.commands.registerCommand(installCopilotLspCommand, async () => {
+            const lspConfigPath = path.join(os.homedir(), '.copilot', 'lsp-config.json');


Think we should probably also check if they have a plugin installed with an lsp.json configured for C#

dibarbet · 2026-05-26T22:41:09Z

    );
+    context.subscriptions.push(
+        vscode.commands.registerCommand(installCopilotLspCommand, async () => {
+            const lspConfigPath = path.join(os.homedir(), '.copilot', 'lsp-config.json');


nit - could we extract this into a separate file & function (similar to other command registrations)

dibarbet · 2026-05-26T22:44:04Z

+            } catch (error) {
+                const nodeError = error as NodeJS.ErrnoException;
+                if (nodeError.code !== 'ENOENT') {
+                    void vscode.window.showErrorMessage(


Instead of manually showing an error message, consider throwing throw Error(msg) - the command infrastructure already seems to handle failures and throw up a modal dialog.

dibarbet · 2026-05-26T22:50:10Z

+                packagedContent = await fs.readFile(extensionLspConfigPath, 'utf8');
+            } catch (error) {
+                const nodeError = error as NodeJS.ErrnoException;
+                void vscode.window.showErrorMessage(


nit - I don't necessarily think it's worth catching this error - we don't expect this to fail, and if it does the command execution should show a modal dialog if it does. Doesn't feel necessary to wrap into a special localized exception

dibarbet · 2026-05-26T22:53:25Z

+            try {
+                updateResult = getUpdatedCopilotLspConfigContent(currentContent, packagedContent);
+            } catch (error) {
+                const message = error instanceof Error ? error.message : String(error);


Similar to before, I don't think we expect this to throw, so imho it is fine to let this bubble up without wrapping into a nice exception

dibarbet · 2026-05-26T23:05:23Z

+    };
+
+    updatedConfig.lspServers!.csharp = packagedCsharpConfig;
+    return { shouldWrite: true, updatedContent: `${JSON.stringify(updatedConfig, null, 2)}\n` };


Could this change the formatting of their file? Maybe not a huge issue, but we've done things like this - https://github.com/dotnet/vscode-csharp/blob/main/src/shared/assets.ts#L1017 before to ensure in place updates

dibarbet · 2026-05-26T23:07:48Z

+
+function containsCSharpServer(lspServers: { [key: string]: unknown }): boolean {
+    for (const [serverName, server] of Object.entries(lspServers)) {
+        if (serverName === 'csharp' || serverContainsCSharpFileExtension(server)) {


Feels like they should both check for extension - I believe server name could be anything.

Also curious what happens if there is already a c# server configured that doesn't use roslyn-language-server.

dibarbet · 2026-05-26T23:14:42Z

    "createTags": "npx ts-node tasks/tags/createTags.ts",
    "fixLocUrls": "npx ts-node tasks/debugger/fixLocUrls.ts",
    "generateOptionsSchema": "npx ts-node tasks/debugger/generateOptionsSchema.ts",
+    "ingest": "npx ts-node tasks/components/ingestCopilotLspConfig.ts",


I don't think this should happen automatically on build - otherwise a build could randomly fail if the config changes.

dibarbet · 2026-05-26T23:15:35Z

+
+function containsCSharpServer(lspServers: { [key: string]: unknown }): boolean {
+    for (const [serverName, server] of Object.entries(lspServers)) {
+        if (serverName === 'csharp' || serverContainsCSharpFileExtension(server)) {


I do also wonder if we could install the lsp config as a plugin (e.g. ship the plugin in the extension, then use CLI commands to install the plugin). And rely on the cli for de-dupe? Not sure if thats any better though

dibarbet · 2026-05-26T23:24:44Z

        logDirectory: context.logUri.fsPath,
        determineBrowserType: BlazorDebugConfigurationProvider.determineBrowserType,
        experimental: {
+            getTreatmentVariable: <T extends boolean | number | string>(name: string, configId = 'vscode') =>


What is actually using / plan to be using this export? Doesn't appear to be for tests, so maybe we delete?

phil-allen-msft added 20 commits May 20, 2026 11:39

Initial implementation

74e515c

Please author a command in this vscode extension that will make the a…

411a8d1

…bove fullConfig changes to the lsp-config.json file if it exists, and write a new lsp-config.json file if it doesn't exist, assuming the .copilot folder does exist.

Change it so that #sym:csharpLspServerConfig is read from a file incl…

29ad016

…uded in the vsix. Copy the file from the dotnet/skills repo now.

As part of the update code, check and see if the lsp-config.json file…

45ed73a

… on the user's machine already contains content for the roslyn-language-server. If so, make no changes.

Now refactor as necessary and add a test so that if the 'install rosl…

ecda5a5

…yn-language-server for Copilot CLI' runs multiple times, the resulting lsp-config.json has exactly the same contents as the copy of the file shipped with the product initially.

Fixup: Add tests

6f84fed

Add a command to the npm build system as 'npm run ingest' which will …

4140a06

…do the same copy that you did earlier of the lsp-config.json from the dotnet/skills repo, but do it again when 'npm run ingest' is specifically run.

Code review the changes that have been committed but are 'ahead' of m…

684a7e6

…ain. Change the Roslyn detection logic such that if there is a lspServer.csharp object in the read lsp-config.json, that counts as Roslyn detection = true

Change the name of the folder that contains lsp-config.json in this r…

b673308

…epo and in the eventual extension to be 'redist'. Update all references.

Rename the configure command to be 'install' so that it mirrors the n…

2e434ea

…aming for the uninstall command

Change how to determine if the lsp is installed. Instead of looking f…

0efb779

…or an object named 'csharp', look for an object that lists ".cs" in the "fileExtensions" collection. Use lsp-config.json in the redist folder as a guide.

Change the method #sym:getUninstalledCopilotLspConfigContent to also …

60b0ab3

…search for content to delete by looking for an lspServer object that has a "fileExtensions" with ".cs"

Change all of the methods that are new in this branch as compared to …

426c84a

…origin/main such that if they contained #sym:RoslynLanguageServer , they instead contain CSharpLsp

Code review all code on the branch as compared to origin/main

6890590

Fix element 1 in the above list. (create .copilot file if necessary)

Remove "%configuration.dotnet.experiments.targetPopulation...% keys,"…

878d50d

… from the package.json file Now remove the "dotnet.experiments.targetPopulation" property from package.json

Fix 4 from the list above

e1b403e

Update message text to reflect current behavior

Change the ingest code so that if the lspServers.csharp element does …

849edb5

…not exist, it reports an error

Local Code Review feedback taken

a12608b

phil-allen-msft requested a review from a team as a code owner May 22, 2026 17:08

jasonmalinowski reviewed May 22, 2026

View reviewed changes

dibarbet reviewed May 26, 2026

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