[BUG] Schema.slack.types.blocks validation rejecting empty optional workflow input parameter

[mfcarroll]

The deno-slack versions

    "deno-slack-sdk/": "https://deno.land/x/deno_slack_sdk@2.15.1/",
    "deno-slack-api/": "https://deno.land/x/deno_slack_api@2.8.0/",

Deno runtime version

deno 1.46.2 (stable, release, aarch64-apple-darwin)
v8 12.9.202.5-rusty
typescript 5.5.2

OS info

ProductName:		macOS
ProductVersion:		15.5
BuildVersion:		24F74
Darwin Kernel Version 24.5.0: Tue Apr 22 19:54:29 PDT 2025; root:xnu-11417.121.6~2/RELEASE_ARM64_T6030

Describe the bug

When I add a webhook to my deno app, and include blocks as an input parameter to be able to post messages from external tools, the validation rejects any post that does not include the blocks parameter, even though that parameter is not set as required. This is different behaviour to all other types, which are ignored if they are not required, and not present.

Steps to reproduce

1. Install demo
2. Create trigger: slack trigger create --trigger-def "./webhook_trigger.ts"
3. Attempt to post to trigger's webhook url:

curl --location 'https://hooks.slack.com/triggers/your_webhook_url' \
--header 'Content-Type: application/json' \
--data '{"channelId": "your_channel_id","blocks": [{"type": "section","text": {"type": "plain_text","text": "This is a blocks test."}}]}'

curl --location 'https://hooks.slack.com/triggers/your_webhook_url' \
--header 'Content-Type: application/json' \
--data '{"channelId": "your_channel_id","text": "This is a text test."}'

Expected result

Both messages should post. Blocks parameter should be ignored when text parameter is present since neither are required.

Actual result

Only the blocks message posts.

2025-06-26 18:53:55 [error] [Wf093BLC11K6] (Trace=Tr0938G1TZLM) Trigger for workflow 'Webhook Notification' failed: parameter_validation_failed
2025-06-26 18:53:55 [error] [Wf093BLC11K6] (Trace=Tr0938G1TZLM)   - Validation for parameter `blocks` failed: invalid_blocks

Details:
failed to match all allowed schemas [json-pointer:/0/text]
must be more than 0 characters [json-pointer:/0/text/text]

Thanks

[hello-ashleyintech]

hi, @mfcarroll! Thanks so much for submitting this issue!

Are you receiving any errors / messaging / logs when posting to the webhook with only text?

[mfcarroll]

Sorry for the ambiguity. The error only occurs with the second example command above, i.e. when posting using just the text parameter, without a blocks parameter present in the request.

Working request, specifying the blocks parameter:

Request:

curl --location 'https://hooks.slack.com/triggers/*****' \
--header 'Content-Type: application/json' \
--data '{"channelId": "your_channel_id","blocks": [{"type": "section","text": {"type": "plain_text","text": "This is a blocks test."}}]}'

Response:

{
    "ok": true
}

Logs:

2025-06-27 18:13:51 [info] [Fn093HBY68CC] (Trace=Tr09326CAAUF) Function 'Webhook Notification' (workflow function) started
{
  toFetchResponse: [Function: toFetchResponse],
  ok: true,
  channel: "C08CVGPD3KJ",
  ts: "1751073233.533879",
  message: {
    user: "U093VQGRB0R",
    type: "message",
    ts: "1751073233.533879",
    bot_id: "B093VQGPXCZ",
    app_id: "A093HBY5W12",
    trigger_id: "Ft093GEKS19Q",
    text: "This is a test.",
    team: "T46QY88RM",
    bot_profile: {
      id: "B093VQGPXCZ",
      app_id: "A093HBY5W12",
      user_id: "U093VQGRB0R",
      name: "webhook-bug-demo (local)",
      icons: {
        image_36: "https://a.slack-edge.com/80588/img/plugins/app/bot_36.png",
        image_48: "https://a.slack-edge.com/80588/img/plugins/app/bot_48.png",
        image_72: "https://a.slack-edge.com/80588/img/plugins/app/service_72.png"
      },
      deleted: false,
      updated: 1751073175,
      team_id: "T46QY88RM"
    },
    blocks: [
      {
        type: "section",
        block_id: "rUjQo",
        text: { type: "plain_text", text: "This is a test.", emoji: true }
      }
    ]
  }
}
2025-06-27 18:13:51 [info] [Wf093HBY68DS] (Trace=Tr09326CAAUF) Workflow 'Webhook Notification' started
2025-06-27 18:13:51 [info] [Wf093HBY68DS] (Trace=Tr09326CAAUF) Workflow step 1 of 1 started
2025-06-27 18:13:52 [info] [Fn093HBY679S] (Trace=Tr09326CAAUF) Function 'Post Message From Webhook' (app function) started
2025-06-27 18:13:53 [info] [Fn093HBY679S] (Trace=Tr09326CAAUF) Function 'Post Message From Webhook' (app function) completed
2025-06-27 18:13:54 [info] [Wf093HBY68DS] (Trace=Tr09326CAAUF) Workflow step 'Post Message From Webhook' completed
2025-06-27 18:13:56 [info] [Fn093HBY68CC] (Trace=Tr09326CAAUF) Function 'Webhook Notification' (workflow function) completed
2025-06-27 18:13:56 [info] [Wf093HBY68DS] (Trace=Tr09326CAAUF) Workflow 'Webhook Notification' completed

Failed request, specifying the text paramter

Request:

curl --location 'https://hooks.slack.com/triggers/*****' \
--header 'Content-Type: application/json' \
--data '{"channelId": "your_channel_id","text": "This is a text test."}'

Response:

{
    "ok": false,
    "error": "invalid_workflow_input"
}

Logs:

2025-06-27 18:24:38 [error] [Wf093HBY68DS] (Trace=Tr093E61L7T7) Trigger for workflow 'Webhook Notification' failed: parameter_validation_failed
2025-06-27 18:24:38 [error] [Wf093HBY68DS] (Trace=Tr093E61L7T7)   - Validation for parameter `blocks` failed: invalid_blocks

Details:
failed to match all allowed schemas [json-pointer:/0/text]
must be more than 0 characters [json-pointer:/0/text/text]

Hope that's more clear.

[hello-ashleyintech]

@mfcarroll thank you so much for sharing more info! I found this example CURL request in the docs here for text-only, could you try it with your webhook URL and let me know if It works? (making sure to include the proper headers)

-d "text=Hi I am a bot that can post messages to any public channel." -d "channel=C123456" -H "Authorization: Bearer xoxb-not-a-real-token-this-will-not-work" -X POST https://hooks.slack.com/triggers/*****