Resolve placeholders before parsing request headers

Contribution Overview

The Engineering Context

This contribution was made to the spring-cloud/spring-cloud-openfeignopen-source repository. The work involved understanding the existing codebase, identifying the underlying engineering problem, implementing a focused solution, and validating the change against the project's existing behaviour and testing standards.

Engineering Problem

Understanding the Problem

Spring Cloud OpenFeign resolved placeholders used inside individual header names or values, but did not resolve a placeholder representing the complete RequestMapping.headers expression before parsing it. As a result, a configuration value that resolved to a complete name=value header expression could not be handled correctly.

Solution

Implementation Approach

Updated the header parsing flow to resolve the complete header expression before locating and parsing the equals separator. Added regression coverage for a placeholder that resolves to an entire name=value RequestMapping header expression while preserving the existing placeholder behaviour.

Technologies

Engineering Stack