cloudformation package stops escaping non-ASCII/emoji characters in YAML double-quoted strings starting from 2.34.13` #10185
Description
Describe the bug
aws cloudformation package stopped escaping non-ASCII/emoji characters in YAML double-quoted strings starting from 2.34.13. Older versions serialized them as YAML unicode escape sequences (e.g. \U0001F6A8), newer versions write raw UTF-8 bytes instead, which CloudFormation cannot display correctly.
Regression Issue
- Select this option if this issue appears to be a regression.
Expected Behavior
Emoji characters inside Fn::Sub are serialized as YAML unicode escapes (2.34.12 output):
}}{{ if eq .Status `firing` }}\U0001F6A8{{ else if eq .Status `resolved` }}\U0001F7E2{{ else }}\U0001F7E1{{ end }}{{ end }}
Current Behavior
Starting from 2.34.13, emojis are written as raw UTF-8 bytes (2.34.22 output):
}}{{ if eq .Status `firing` }}🚨{{ else if eq .Status `resolved` }}🟢{{ else }}🟡{{ end }}{{ end }}
This causes CloudFormation Stack to display ? instead of emojis in the console and via aws cloudformation get-template.
Reproduction Steps
- Create
dummy-cf.yaml:
AWSTemplateFormatVersion: '2010-09-09'
Parameters:
EnvName:
Type: String
Default: test
Resources:
TestResource:
Type: AWS::SSM::Parameter
Properties:
Name: !Sub "${EnvName}-test"
Type: String
Value:
Fn::Sub:
- |
template_files:
slack_template: |
{{ define "sns.slack.status_emoji" }}{{ if eq .Status `firing` }}🚨{{ else if eq .Status `resolved` }}🟢{{ else }}🟡{{ end }}{{ end }}
{{ define "sns.slack.message" }}
{{- $envName := printf "%s" "${EnvName}" -}}
{{- $queryExprTemplated := reReplaceAll "\\]" "%5D" (
reReplaceAll "\\[" "%5B" (
reReplaceAll "=" "%3D" (
reReplaceAll "\\}" "%7D" (
reReplaceAll "\\{" "%7B" (
reReplaceAll ">" "%3E" (
reReplaceAll "<" "%3C" (
reReplaceAll " " "%20" (
reReplaceAll "\"" "%22" (
reReplaceAll "'" "%27" (
$envName
)))))))))) }}
{{ end }}
- {}- Run:
docker run --rm -v $(pwd):/workspace amazon/aws-cli:2.34.12 \
cloudformation package \
--template-file /workspace/dummy-cf.yaml \
--output-template-file /workspace/packaged-2.34.12.yml \
--s3-bucket dummy-bucket
docker run --rm -v $(pwd):/workspace amazon/aws-cli:2.34.22 \
cloudformation package \
--template-file /workspace/dummy-cf.yaml \
--output-template-file /workspace/packaged-2.34.22.yml \
--s3-bucket dummy-bucket
diff packaged-2.34.12.yml packaged-2.34.22.yml- Diff output:
< \ }}{{ if eq .Status `firing` }}\U0001F6A8{{ else if eq .Status `resolved`\
< \ }}\U0001F7E2{{ else }}\U0001F7E1{{ end }}{{ end }}\n {{ define "sns.slack.message"\
---
> \ }}{{ if eq .Status `firing` }}🚨{{ else if eq .Status `resolved` }}🟢{{\
> \ else }}🟡{{ end }}{{ end }}\n {{ define "sns.slack.message" }}\n \Possible Solution
Most likely same root cause as #10156 — the ruamel.yaml upgrade from 0.17.21 to 0.19.1 introduced in 2.34.13 alongside the Python 3.14.3 interpreter upgrade. The new version likely changed how non-ASCII characters are handled during YAML serialization.
Additional Information/Context
Functionally emojis still work — downstream services (tested on AMP Alermanager) receive and display them correctly. The impact is that CloudFormation shows ? in the console and get-template output, making it hard to verify what is actually deployed.
CLI version used
2.34.22
Environment details (OS name and version, etc.)
Reproduced using official amazon/aws-cli Docker images on macOS