Description

Logger plugins run an access-phase handler to capture request bodies. This caused _meta.filter expressions that reference response variables to be evaluated before those variables were available, with the access-phase result reused during the log phase. Reading $status during access also cached 0 in ctx.var, which could affect other plugins on the same request.

This change:

• scopes _meta.filter result caching to each execution phase, while retaining caching for repeated callbacks within the same phase
• prevents $status from being cached because its value changes after the response status is determined
• adds regression coverage for response-phase filters and cross-plugin status isolation

Which issue(s) this PR fixes:

Fixes #13724

Tests

• prove -I. -r t/core/ctx2.t
• prove -I. -r t/plugin/file-logger3.t
• prove -I. -r t/plugin/plugin.t
• prove -I. -r t/plugin/file-logger.t t/plugin/file-logger2.t
• ./utils/lj-releng apisix/plugin.lua apisix/core/ctx.lua

The issue scenarios were also reproduced on APISIX 3.17.0 and verified against the patched source. Gateway-generated 404 responses are filtered as configured, while upstream 200 and 404 responses are logged with their actual status values.

Checklist

• I have explained the need for this PR and the problem it solves
• I have explained the changes or the new features added to this PR
• I have added tests corresponding to this change
• I have updated the documentation to reflect this change (Not applicable: this restores existing behavior without changing configuration or public APIs.)
• I have verified that this change is backward compatible (If not, please discuss on the APISIX mailing list first)