claude-code-action/src/mcp/install-mcp-server.ts

import * as core from "@actions/core";

type PrepareConfigParams = {
  githubToken: string;
  owner: string;
  repo: string;
  branch: string;
  additionalMcpConfig?: string;
  claudeCommentId?: string;
  allowedTools?: string;
};

export async function prepareMcpConfig(
  params: PrepareConfigParams,
): Promise<string> {
  const {
    githubToken,
    owner,
    repo,
    branch,
    additionalMcpConfig,
    claudeCommentId,
    allowedTools,
  } = params;
  try {
    // Parse allowed tools into an array
    const allowedToolsList = allowedTools
      ? allowedTools.split(",").map((tool) => tool.trim())
      : [];

    // Check if any GitHub MCP tools are allowed
    const hasGitHubMcpTools = allowedToolsList.some((tool) =>
      tool.startsWith("mcp__github__"),
    );

    // Start with an empty servers object
    const mcpServers: Record<string, any> = {};

    // Only include github MCP server if GitHub tools are allowed
    if (hasGitHubMcpTools) {
      mcpServers.github = {
        command: "docker",
        args: [
          "run",
          "-i",
          "--rm",
          "-e",
          "GITHUB_PERSONAL_ACCESS_TOKEN",
          "ghcr.io/github/github-mcp-server:sha-e9f748f", // https://github.com/github/github-mcp-server/releases/tag/v0.4.0
        ],
        env: {
          GITHUB_PERSONAL_ACCESS_TOKEN: githubToken,
        },
      };
    }

    // Always include github_file_ops server as it contains essential tools
    // (mcp__github_file_ops__commit_files, mcp__github_file_ops__update_claude_comment)
    // These are in the BASE_ALLOWED_TOOLS and should always be available
    mcpServers.github_file_ops = {
      command: "bun",
      args: [
        "run",
        `${process.env.GITHUB_ACTION_PATH}/src/mcp/github-file-ops-server.ts`,
      ],
      env: {
        GITHUB_TOKEN: githubToken,
        REPO_OWNER: owner,
        REPO_NAME: repo,
        BRANCH_NAME: branch,
        REPO_DIR: process.env.GITHUB_WORKSPACE || process.cwd(),
        ...(claudeCommentId && { CLAUDE_COMMENT_ID: claudeCommentId }),
        GITHUB_EVENT_NAME: process.env.GITHUB_EVENT_NAME || "",
        IS_PR: process.env.IS_PR || "false",
      },
    };

    const baseMcpConfig = {
      mcpServers,
    };

    // Merge with additional MCP config if provided
    if (additionalMcpConfig && additionalMcpConfig.trim()) {
      try {
        const additionalConfig = JSON.parse(additionalMcpConfig);

        // Validate that parsed JSON is an object
        if (typeof additionalConfig !== "object" || additionalConfig === null) {
          throw new Error("MCP config must be a valid JSON object");
        }

        core.info(
          "Merging additional MCP server configuration with built-in servers",
        );

        // Merge configurations with user config overriding built-in servers
        const mergedConfig = {
          ...baseMcpConfig,
          ...additionalConfig,
          mcpServers: {
            ...baseMcpConfig.mcpServers,
            ...additionalConfig.mcpServers,
          },
        };

        return JSON.stringify(mergedConfig, null, 2);
      } catch (parseError) {
        core.warning(
          `Failed to parse additional MCP config: ${parseError}. Using base config only.`,
        );
      }
    }

    return JSON.stringify(baseMcpConfig, null, 2);
  } catch (error) {
    core.setFailed(`Install MCP server failed with error: ${error}`);
    process.exit(1);
  }
}