Backport(v1.19): Add allow_comments: true option for json parser (#5428) - #5432
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**Which issue(s) this PR fixes**: Fixes # **What this PR does / why we need it**: Related to #5410 Since json gem 3.0, JSON.parse will raise an error when the input contains comments unless `allow_comments: true` is passed. On Ruby head this already shows up as a deprecation warning: ``` warning: Encountered comment in JSON. This will raise an error in json 3.0 unless enabled via `allow_comments: true` ``` Ref. https://github.com/ruby/json/blob/master/CHANGES.md#2026-06-23-2200 Fluentd has accepted comments in JSON so far (embedded JSON in the config parsed by literal_parser, and the json parser plugin), so add `allow_comments: true` to `DEFAULT_JSON_PARSE_OPTIONS` to keep that behavior and avoid the future breakage. Ref. https://github.com/fluent/fluentd/blob/43f46f33efb3e6dda17576568c313b3f758dfa0c/test/config/test_literal_parser.rb#L275-L277 This constant is shared by both paths, so the single change covers them together. **Docs Changes**: **Release Note**: * Add `allow_comments: true` option for json parser Signed-off-by: Shizuo Fujita <fujita@clear-code.com> Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Watson1978
approved these changes
Jul 13, 2026
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Which issue(s) this PR fixes:
Backport #5428
Fixes #
What this PR does / why we need it:
Related to #5410
Since json gem 3.0, JSON.parse will raise an error when the input contains comments unless
allow_comments: trueis passed. On Ruby head this already shows up as a deprecation warning:Ref. https://github.com/ruby/json/blob/master/CHANGES.md#2026-06-23-2200
Fluentd has accepted comments in JSON so far (embedded JSON in the config parsed by literal_parser, and the json parser plugin), so add
allow_comments: truetoDEFAULT_JSON_PARSE_OPTIONSto keep that behavior and avoid the future breakage.Ref.
fluentd/test/config/test_literal_parser.rb
Lines 275 to 277 in 43f46f3
This constant is shared by both paths, so the single change covers them together.
Docs Changes:
Release Note:
allow_comments: trueoption for json parser