Fix NPE in Gson when serializing request headers on cold start

[faraz152]

Summary

• Fixes NPE in TypeVariableImpl.hashCode when serializing request headers (Gson) on cold start #1602 — ChuckerInterceptor crashes on cold start with NullPointerException in TypeVariableImpl.hashCode() when Gson tries to serialize request headers via reflection
• Wraps JsonConverter.instance.toJson(headers) in try-catch in both setRequestHeaders and setResponseHeaders so the interceptor never crashes the request thread

Root cause

On cold start (after long idle), Gson's internal reflection for List<HttpHeader> type resolution triggers a NullPointerException in libcore.reflect.TypeVariableImpl.hashCode(). This is a known JVM/Android runtime edge case where type metadata hasn't been fully initialized.

Changes

• HttpTransaction.kt — Added defensive try-catch around both setRequestHeaders and setResponseHeaders serialization calls
• On failure, falls back to plain-text header representation (name: value per line) so the transaction is still recorded

Test plan

• Existing unit tests pass (testDebugUnitTest)
• Build compiles successfully
• Fallback produces readable header output instead of crashing
• Manual: Install with Chucker after long idle → first request should not crash

🤖 Generated with Claude Code

[cortinico]

Thanks for looking into this @faraz152 - there are a couple of things to fix though

[cortinico]

This won't work sadly. The caller will always assume the field contains a JSON string:

chucker/library/src/main/kotlin/com/chuckerteam/chucker/internal/data/entity/HttpTransaction.kt

Lines 174 to 178 in 2054c4b

	fun getParsedRequestHeaders(): List<HttpHeader>? =
	JsonConverter.instance.fromJson<List<HttpHeader>>(
	requestHeaders,
	TypeToken.getParameterized(List::class.java, HttpHeader::class.java).type,
	)

So you should store it as valid JSON, not as plain string.

What would happen is that you will show nothing to the user even if headers are there.

[cortinico]

Once you do the other changes, can you refactor so that this code is inside a util function + add tests?

[faraz152]

Thanks @cortinico, good catch. Pushed an update that addresses both points:

• The fallback no longer stores a plain name: value string. It now builds a real JSON array via Gson's JsonArray/JsonObject tree API (which skips the reflective element-type resolution that was blowing up), so getParsedRequestHeaders() / getParsedResponseHeaders() still round-trip correctly.
• Extracted the logic into HttpHeaderSerializer in internal/support and added HttpHeaderSerializerTest covering: default path round-trip, empty list, fallback round-trip, and fallback escaping of quotes/control chars.
• ktlint + detekt are clean locally.

[faraz152]

@cortinico — CI is also showing action_required here (needs a maintainer to approve the workflow run). Let me know if you'd like any changes to the HttpHeaderSerializer implementation while you're reviewing.