Output of slack.post_message not parsing '\n'

[mbrannigan]

SUMMARY

Code snippets:

# workflows/list_instances.yaml
      finish:
        action: centro.post_message
        input:
          channel: <% $.channel %>
          module_name: <% $.module_name %>
          environment: <% $.environment %>
          execution_id: <% $.execution_id %>
          user: <% $.user %>
          message: "```<% $.instance_list %>```"
        on-complete:
          - succeed

# chains/post_message.yaml
---
  chain:
    -
      name: "post_message"
      ref: "slack.post_message"
      parameters:
        username: "marvin"
        channel: "{{ channel }}"
        icon_emoji: ":marvin:"
        message: "[{{ module_name }} | {{ environment }} | {{ execution_id }} | {{ user }}] - {{ message }}"

In the previous install of st2, \n characters were honored and produced newlines in the output to slack. In the 2.7.2 release the \n characters get output, munging the output into a single line of output.

ISSUE TYPE

Pick one below and delete the rest:

• Bug Report

STACKSTORM VERSION

st2 2.7.2, on Python 2.7

OS / ENVIRONMENT / INSTALL METHOD

CentOS Linux release 7.5.1804 (Core)
Installation method:
curl -sSL https://stackstorm.com/packages/install.sh | bash -s -- --user=st2admin --password='REDACTED' --version="${st2_version}"

STEPS TO REPRODUCE

This outputs the same way ever time.

EXPECTED RESULTS

Expected output:

     Instance Id        State       IP Addr          Started         Avail Zone      Type       Environment        Role                 Full Name           
--------------------- ---------- ------------- -------------------- ------------ ------------ --------------- --------------- ------------------------------
i-0ab70a085095ff8f4   running    10.50.13.191  2018-08-08 15:15:54  us-west-2c   m5.large     staging02       biexport-worker biexport-worker-green_staging02
i-0c041493c86994868   running    10.50.12.76   2018-08-08 15:15:39  us-west-2b   m4.xlarge    staging02       cmm_web         cmm-green_staging02           
i-099b501ee05e2eb50   running    10.50.12.8    2018-05-01 03:22:48  us-west-2b   t2.medium    staging02       metabase        metabase-staging02            

ACTUAL RESULTS

     Instance Id        State       IP Addr          Started         Avail Zone      Type       Environment        Role                 Full Name           \n--------------------- ---------- ------------- -------------------- ------------ ------------ --------------- --------------- ------------------------------\ni-0ab70a085095ff8f4   running    10.50.13.191  2018-08-08 15:15:54  us-west-2c   m5.large     staging02       biexport-worker biexport-worker-green_staging02\ni-0c041493c86994868   running    10.50.12.76   2018-08-08 15:15:39  us-west-2b   m4.xlarge    staging02       cmm_web         cmm-green_staging02           \ni-099b501ee05e2eb50   running    10.50.12.8    2018-05-01 03:22:48  us-west-2b   t2.medium    staging02       metabase        metabase-staging02            \n ... 

[mbrannigan]

Workaround provided by @LindsayHill:

# chains/post_message.yaml
---
  chain:
    -
      name: "post_message"
      ref: "slack.post_message"
      parameters:
        username: "marvin"
        channel: "{{ channel }}"
        icon_emoji: ":marvin:"
        message: "[{{ module_name }} | {{ environment }} | {{ execution_id }} | {{ user }}] - {{ message.replace('\\\\n', '\\n') }}"