refactor: improve discriminated union implementation based on review feedback

- Use eventName checks instead of 'in' operator for more robust type guards
- Remove unnecessary type assertions - TypeScript's control flow analysis works correctly
- Remove redundant runtime checks for entityNumber and isPR
- Simplify code by using context directly after type guard

Co-Authored-By: Claude <noreply@anthropic.com>

src/entrypoints/update-comment-link.ts

@@ -10,7 +10,6 @@ import {
   parseGitHubContext,
   isPullRequestReviewCommentEvent,
   isEntityContext,
-  type ParsedGitHubContext,
 } from "../github/context";
 import { GITHUB_SERVER_URL } from "../github/api/config";
 import { checkAndCommitOrDeleteBranch } from "../github/operations/branch-cleanup";
@@ -31,9 +30,7 @@ async function run() {
       throw new Error("update-comment-link requires an entity context");
     }
 
-    // TypeScript needs a type assertion here due to control flow limitations
-    const entityContext = context as ParsedGitHubContext;
-    const { owner, repo } = entityContext.repository;
+    const { owner, repo } = context.repository;
 
     const octokit = createOctokit(githubToken);
 
@@ -46,7 +43,7 @@ async function run() {
     try {
       // GitHub has separate ID namespaces for review comments and issue comments
       // We need to use the correct API based on the event type
-      if (isPullRequestReviewCommentEvent(entityContext)) {
+      if (isPullRequestReviewCommentEvent(context)) {
         // For PR review comments, use the pulls API
         console.log(`Fetching PR review comment ${commentId}`);
         const { data: prComment } = await octokit.rest.pulls.getReviewComment({
@@ -75,16 +72,16 @@ async function run() {
       // If all attempts fail, try to determine more information about the comment
       console.error("Failed to fetch comment. Debug info:");
       console.error(`Comment ID: ${commentId}`);
-      console.error(`Event name: ${entityContext.eventName}`);
-      console.error(`Entity number: ${entityContext.entityNumber}`);
-      console.error(`Repository: ${entityContext.repository.full_name}`);
+      console.error(`Event name: ${context.eventName}`);
+      console.error(`Entity number: ${context.entityNumber}`);
+      console.error(`Repository: ${context.repository.full_name}`);
 
       // Try to get the PR info to understand the comment structure
       try {
         const { data: pr } = await octokit.rest.pulls.get({
           owner,
           repo,
-          pull_number: entityContext.entityNumber,
+          pull_number: context.entityNumber,
         });
         console.log(`PR state: ${pr.state}`);
         console.log(`PR comments count: ${pr.comments}`);
@@ -136,12 +133,12 @@ async function run() {
             comparison.total_commits > 0 ||
             (comparison.files && comparison.files.length > 0)
           ) {
-            const entityType = entityContext.isPR ? "PR" : "Issue";
+            const entityType = context.isPR ? "PR" : "Issue";
             const prTitle = encodeURIComponent(
-              `${entityType} #${entityContext.entityNumber}: Changes from Claude`,
+              `${entityType} #${context.entityNumber}: Changes from Claude`,
             );
             const prBody = encodeURIComponent(
-              `This PR addresses ${entityType.toLowerCase()} #${entityContext.entityNumber}\n\nGenerated with [Claude Code](https://claude.ai/code)`,
+              `This PR addresses ${entityType.toLowerCase()} #${context.entityNumber}\n\nGenerated with [Claude Code](https://claude.ai/code)`,
             );
             const prUrl = `${serverUrl}/${owner}/${repo}/compare/${baseBranch}...${claudeBranch}?quick_pull=1&title=${prTitle}&body=${prBody}`;
             prLink = `\n[Create a PR](${prUrl})`;

src/modes/tag/index.ts

@@ -8,10 +8,7 @@ import { configureGitAuth } from "../../github/operations/git-config";
 import { prepareMcpConfig } from "../../mcp/install-mcp-server";
 import { fetchGitHubData } from "../../github/data/fetcher";
 import { createPrompt } from "../../create-prompt";
-import {
-  isEntityContext,
-  type ParsedGitHubContext,
-} from "../../github/context";
+import { isEntityContext } from "../../github/context";
 
 /**
  * Tag mode implementation.
@@ -59,37 +56,33 @@ export const tagMode: Mode = {
     octokit,
     githubToken,
   }: ModeOptions): Promise<ModeResult> {
-    // Tag mode handles entity-based events (issues, PRs, comments)
-    // We know context is ParsedGitHubContext for tag mode
-    const entityContext = context as ParsedGitHubContext;
+    // Tag mode only handles entity-based events
+    if (!isEntityContext(context)) {
+      throw new Error("Tag mode requires entity context");
+    }
 
     // Check if actor is human
-    await checkHumanActor(octokit.rest, entityContext);
+    await checkHumanActor(octokit.rest, context);
 
     // Create initial tracking comment
-    const commentData = await createInitialComment(octokit.rest, entityContext);
+    const commentData = await createInitialComment(octokit.rest, context);
     const commentId = commentData.id;
 
-    // Fetch GitHub data - entity events always have entityNumber and isPR
-    if (!entityContext.entityNumber || entityContext.isPR === undefined) {
-      throw new Error("Entity events must have entityNumber and isPR defined");
-    }
-
     const githubData = await fetchGitHubData({
       octokits: octokit,
-      repository: `${entityContext.repository.owner}/${entityContext.repository.repo}`,
-      prNumber: entityContext.entityNumber.toString(),
-      isPR: entityContext.isPR,
-      triggerUsername: entityContext.actor,
+      repository: `${context.repository.owner}/${context.repository.repo}`,
+      prNumber: context.entityNumber.toString(),
+      isPR: context.isPR,
+      triggerUsername: context.actor,
     });
 
     // Setup branch
-    const branchInfo = await setupBranch(octokit, githubData, entityContext);
+    const branchInfo = await setupBranch(octokit, githubData, context);
 
     // Configure git authentication if not using commit signing
     if (!context.inputs.useCommitSigning) {
       try {
-        await configureGitAuth(githubToken, entityContext, commentData.user);
+        await configureGitAuth(githubToken, context, commentData.user);
       } catch (error) {
         console.error("Failed to configure git authentication:", error);
         throw error;
@@ -97,26 +90,26 @@ export const tagMode: Mode = {
     }
 
     // Create prompt file
-    const modeContext = this.prepareContext(entityContext, {
+    const modeContext = this.prepareContext(context, {
       commentId,
       baseBranch: branchInfo.baseBranch,
       claudeBranch: branchInfo.claudeBranch,
     });
 
-    await createPrompt(tagMode, modeContext, githubData, entityContext);
+    await createPrompt(tagMode, modeContext, githubData, context);
 
     // Get MCP configuration
     const additionalMcpConfig = process.env.MCP_CONFIG || "";
     const mcpConfig = await prepareMcpConfig({
       githubToken,
-      owner: entityContext.repository.owner,
-      repo: entityContext.repository.repo,
+      owner: context.repository.owner,
+      repo: context.repository.repo,
       branch: branchInfo.claudeBranch || branchInfo.currentBranch,
       baseBranch: branchInfo.baseBranch,
       additionalMcpConfig,
       claudeCommentId: commentId.toString(),
-      allowedTools: entityContext.inputs.allowedTools,
-      context: entityContext,
+      allowedTools: context.inputs.allowedTools,
+      context,
     });
 
     core.setOutput("mcp_config", mcpConfig);