Extended list for environment variables don't work

[chris-dietz]

Bug Report

Describe the bug
The official documentation for YAML Environment Variables documents an "Extended list form" for the env section (using - name: ..., uri: ..., refresh_interval: ...).

However, using this documented syntax causes Fluent Bit to fail on startup with a YAML parse error:
unexpected event 'sequence-start-event' (7) in state 'env' (41).

The YAML parser (flb_cf_yaml.c) state machine for STATE_ENV strictly expects a mapping (YAML_MAPPING_START_EVENT) and rejects sequences (YAML_SEQUENCE_START_EVENT), making the documented extended list syntax completely unusable.

To Reproduce

• Example log message:

[error] [config] YAML error found in file "/fluent-bit/etc/fluent-bit.yaml", line 2, column 2: unexpected event 'sequence-start-event' (7) in state 'env' (41).
[error] yaml error
[error] configuration file contains errors, aborting.

• Steps to reproduce the problem:
  1. Create a fluent-bit.yaml file with the exact example from the documentation:

     env:
       - name: DB_PASSWORD
         uri: file:///run/secrets/db_password
         refresh_interval: 60
       - name: REGION
         value: us-east-1
     
     service:
       flush: 1
       log_level: info
     
     pipeline:
       inputs:
         - name: dummy
       outputs:
         - name: stdout
           match: '*'

  2. Run Fluent Bit:

     fluent-bit -c fluent-bit.yaml

  3. Fluent Bit aborts during configuration parsing.

Expected behavior
Either:

1. The YAML configuration parser should support the documented extended list form for dynamic secret/file loading under env:, OR
2. The documentation should be updated/corrected to state that only the map form (env: KEY: value) is supported, removing the invalid extended list examples.

Your Environment

• Version used: 4.2.7 (reproduced on fluent/fluent-bit:4.2.7-debug)
• Configuration: Minimal YAML configuration containing the documented env: list syntax
• Environment name and version: Docker / Container
• Operating System and version: Linux

Additional context
Documented at: https://docs.fluentbit.io/manual/4.2/administration/configuring-fluent-bit/yaml/environment-variables-section#extended-list-form