Add option to skip updating or recreating comments when message is unchanged

src/comment.ts

@@ -15,6 +15,10 @@ function headerComment(header: String): string {
   return `<!-- Sticky Pull Request Comment${header} -->`
 }
 
+function bodyWithHeader(body: string, header: string): string {
+  return `${body}\n${headerComment(header)}`
+}
+
 export async function findPreviousComment(
   octokit: InstanceType<typeof GitHub>,
   repo: {
@@ -100,7 +104,7 @@ export async function updateComment(
         id,
         body: previousBody
           ? `${previousBody}\n${body}`
-          : `${body}\n${headerComment(header)}`
+          : bodyWithHeader(body, header)
       }
     }
   )
@@ -126,7 +130,7 @@ export async function createComment(
     issue_number,
     body: previousBody
       ? `${previousBody}\n${body}`
-      : `${body}\n${headerComment(header)}`
+      : bodyWithHeader(body, header)
   })
 }
 export async function deleteComment(
@@ -162,7 +166,7 @@ export async function minimizeComment(
 }
 
 export function getBodyOf(
-  previous: {body?: string},
+  previous: {body: string},
   append: boolean,
   hideDetails: boolean
 ): string | undefined {
@@ -176,3 +180,12 @@ export function getBodyOf(
 
   return previous.body?.replace(/(<details.*?)\s*\bopen\b(.*>)/g, "$1$2")
 }
+
+export function commentsEqual(
+  body: string,
+  previous: string,
+  header: string
+): boolean {
+  const newBody = bodyWithHeader(body, header)
+  return newBody === previous
+}

src/config.ts

@@ -28,6 +28,9 @@ export const onlyCreateComment = core.getBooleanInput("only_create", {
 export const onlyUpdateComment = core.getBooleanInput("only_update", {
   required: true
 })
+export const skipUnchanged = core.getBooleanInput("skip_unchanged", {
+  required: true
+})
 export const hideOldComment = core.getBooleanInput("hide", {required: true})
 export const githubToken = core.getInput("GITHUB_TOKEN", {required: true})
 export const ignoreEmpty = core.getBooleanInput("ignore_empty", {

src/main.ts

@@ -14,6 +14,7 @@ import {
   recreate,
   repo,
   ignoreEmpty,
+  skipUnchanged,
   onlyCreateComment,
   onlyUpdateComment
 } from "./config"
@@ -23,7 +24,8 @@ import {
   findPreviousComment,
   getBodyOf,
   minimizeComment,
-  updateComment
+  updateComment,
+  commentsEqual
 } from "./comment"
 
 async function run(): Promise<undefined> {
@@ -99,6 +101,11 @@ async function run(): Promise<undefined> {
       return
     }
 
+    if (skipUnchanged && commentsEqual(body, previous.body, header)) {
+      // don't recreate or update if the message is unchanged
+      return
+    }
+
     const previousBody = getBodyOf(previous, append, hideDetails)
     if (recreate) {
       await deleteComment(octokit, previous.id)