ADR-0014: Fix adapter platform-specific config resolution to follow RFC-0005

Status: proposed | Date: 2026-04-04

References: RFC-0005

Context

Configuration fields like confluence.space, confluence.parent_id, xiaohongshu.subtitle, astro.slug, etc. are platform-specific fields that adapters read to customize their behavior per content item.

Problem Statement

The current implementation of content_info_with_platform() in adapters_impl.rs only populates ContentInfo.platform_extra from the post’s meta.toml platform-specific section (Layer 1). This means global configuration values from typub.toml (Layer 3) are completely ignored.

For example, if a user sets:

# typub.toml
[platforms.confluence]
space = "TEAM"
parent_id = "123456"

And in meta.toml:

[platforms.confluence]
# empty - expects to use global config

The adapter would not see the space or parent_id values because they were only read from post-level config.

Constraints

• Must follow RFC-0005:C-RESOLUTION-ORDER 4-layer resolution
• Must not break existing adapters that use get_platform_str()
• Must handle the case where the same key exists at both post and global levels (post wins)

Decision

Add a new resolve_platform_field() function in resolved_config.rs that implements the 4-layer resolution order for platform-specific string fields:

1. meta.toml[platforms.<platform>].{field} — per-content platform-specific
2. (Skipped for platform-specific fields - no per-content default)
3. typub.toml[platforms.<platform>].{field} — global platform-specific
4. (Skipped for platform-specific fields - no global default)
5. Caller-provided default

Modify content_info_with_platform() to:

1. Collect all unique keys from both post-level and global-level platform config
2. Resolve each key using resolve_platform_field()
3. Populate platform_extra with the resolved values

This approach:

• Maintains backward compatibility: adapters continue to use get_platform_str()
• Follows RFC-0005: implements proper 4-layer resolution
• Is extensible: works for any platform-specific field without adapter changes

Consequences

Positive

• Platform-specific fields now properly follow the RFC-0005 resolution order
• Users can set global defaults in typub.toml and override per-post in meta.toml
• No changes required to adapter code - they continue using get_platform_str()
• Consistent behavior across all adapters (Confluence, Xiaohongshu, Astro, Static, WordPress)

Negative

• content_info_with_platform() now requires a Config parameter (breaking change for external callers)
• Slightly more complex key collection logic compared to the previous simple extraction

Neutral

• Existing tests continue to pass without modification (backward compatible behavior for cases where only Layer 1 was used)