feat: Add ability to create message in another message thread

action.yml

@@ -13,6 +13,9 @@ inputs:
   ts:
     description: "If passed, update matching message instead of posting a new one"
     required: false
+  threadTs:
+    description: "If passed, add message to thread to the message referenced"
+    required: false
   text:
     description: "The message's base text"
     required: false

dist/index.js

@@ -4066,6 +4066,7 @@ async function run() {
     const token = core.getInput("token", { required: true });
     const channel = core.getInput("channel", { required: true });
     const ts = core.getInput("ts", { required: false });
+    const threadTs = core.getInput("threadTs", { required: false });
 
     const text = core.getInput("text", { required: false }) || undefined;
     const blocksRaw = core.getInput("blocks", { required: false }) || undefined;
@@ -4117,6 +4118,26 @@ async function run() {
       return;
     }
 
+    if (threadTs) {
+      // just post a new message but as an thread
+      const message = {
+        channel,
+        text,
+        blocks,
+        attachments,
+        thread_ts: threadTs,
+      };
+      const result = await client.chat.postMessage(message);
+      if (result.error) {
+        throw new Error(
+          `Error while posting slack message as thread: ${result.error}`
+        );
+      }
+      const { ts } = result;
+      core.setOutput("ts", ts);
+      return;
+    }
+
     // retrive the original message
     const response = await client.conversations.history({
       token,

src/index.js

@@ -9,6 +9,7 @@ async function run() {
     const token = core.getInput("token", { required: true });
     const channel = core.getInput("channel", { required: true });
     const ts = core.getInput("ts", { required: false });
+    const threadTs = core.getInput("threadTs", { required: false });
 
     const text = core.getInput("text", { required: false }) || undefined;
     const blocksRaw = core.getInput("blocks", { required: false }) || undefined;
@@ -60,6 +61,26 @@ async function run() {
       return;
     }
 
+    if (threadTs) {
+      // just post a new message but as an thread
+      const message = {
+        channel,
+        text,
+        blocks,
+        attachments,
+        thread_ts: threadTs,
+      };
+      const result = await client.chat.postMessage(message);
+      if (result.error) {
+        throw new Error(
+          `Error while posting slack message as thread: ${result.error}`
+        );
+      }
+      const { ts } = result;
+      core.setOutput("ts", ts);
+      return;
+    }
+
     // retrive the original message
     const response = await client.conversations.history({
       token,