SvelteLS.MCP

Instructions

Implementation Reference

• src/tools/code-actions.ts:107-186 (handler)

  The handler function for 'apply_code_action' which fetches, identifies, resolves, and applies the code action.

  async ({
    filePath,
    startLine,
    actionTitle,
    endLine,
    kind,
  }): Promise<ToolResult> => {
    try {
      const { actions, error } = await fetchCodeActions(
        lsp,
        filePath,
        startLine,
        endLine,
        kind
      );
      if (error) return textResult(error);
      if (!actions) return textResult("No code actions available.");
  
      // Find matching action by partial title
      let match = actions.find((a: any) =>
        (a.title ?? "")
          .toLowerCase()
          .includes(actionTitle.toLowerCase())
      );
  
      // Exact match fallback
      if (!match) {
        match = actions.find(
          (a: any) =>
            (a.title ?? "").toLowerCase() === actionTitle.toLowerCase()
        );
      }
  
      if (!match) {
        return textResult(
          `No code action matching '${actionTitle}' found. Use get_code_actions to see available actions.`
        );
      }
  
      if (match.disabled) {
        return textResult(
          `Code action '${match.title}' is disabled: ${match.disabled.reason}.`
        );
      }
  
      // If action has a direct edit, use it. Otherwise resolve.
      let edit = match.edit;
      if (!edit) {
        const resolved = await lsp.request("codeAction/resolve", match);
        if (!resolved) {
          return textResult(
            `Failed to resolve code action '${match.title}'.`
          );
        }
        edit = resolved.edit;
      }
  
      if (!edit) {
        if (match.command) {
          return textResult(
            `Code action '${match.title}' requires command execution which is not supported.`
          );
        }
        return textResult(
          `Code action '${match.title}' returned no edits.`
        );
      }
  
      const matchTitle = match.title ?? actionTitle;
      const applied = await applyWorkspaceEdit(lsp, edit);
      const summary = formatWorkspaceEdit(edit, `Applied '${matchTitle}'`);
      return textResult(
        applied
          ? summary
          : `(dry-run, edits NOT applied)\n\n${summary}`
      );
    } catch (ex) {
      return textResult(formatError(ex));
    }
  }

• src/tools/code-actions.ts:86-106 (registration)

  Registration of the 'apply_code_action' tool with its schema definition.

  server.registerTool(
    "apply_code_action",
    {
      title: "Apply Code Action",
      description:
        "Apply a code action (quick fix, refactoring) by its title. Use get_code_actions first to see available actions.",
      inputSchema: z.object({
        filePath: z.string().describe("Absolute path to the file"),
        startLine: z.number().describe("Start line (1-based)"),
        actionTitle: z
          .string()
          .describe(
            "Title of the code action to apply (case-insensitive partial match)"
          ),
        endLine: z.number().optional().describe("End line (1-based)"),
        kind: z
          .string()
          .optional()
          .describe("Filter by kind: quickfix, refactor, etc."),
      }),
    },