Fix redirect handling in KtorImageFetcher (#859)

[skydoves]

Summary

Fixes #859. LandscapistImage failed to load images whose URL performs a redirect, reporting SendCountExceedException: Max send count 20 exceeded even though only one redirect was involved. A browser loads the same URL fine.

Two issues in KtorImageFetcher caused this:

• No cookie store. Some CDNs set a cookie on the first response and redirect to a target that requires it. Without retaining the cookie, the target keeps redirecting, looping until the send-count limit is hit. Browsers retain cookies automatically, which is exactly why the URL works in a browser but not here. Now install(HttpCookies) retains the cookie across redirect hops.
• maxSendCount semantics. It was set to maxRedirects, conflating the total number of request dispatches (original + redirects + retries) with the redirect count. That under-allowed redirects by one, and before that setting existed the client used Ktor's default of 20 (matching the reported error). It is now maxRedirects + 1, so the original send plus maxRedirects hops are permitted.

The shared client configuration is extracted into configureForImageLoading so create() and tests build an identical client regardless of engine.

Tests

Adds MockEngine-based regression tests in KtorImageFetcherTest:

• cookieGatedRedirectResolvesInsteadOfLooping — reproduces SendCountExceedException: Max send count 20 exceeded #859; a cookie-gated self-redirect now resolves to success.
• redirectChainWithinMaxRedirectsSucceeds — a chain within maxRedirects is followed.
• redirectChainBeyondMaxRedirectsFails — a longer chain fails with SendCountExceedException instead of looping forever.

All pass on landscapist-core:desktopTest; native and wasm test targets compile.

Notes

• Adds ktor-client-mock as a commonTest dependency.
• The default User-Agent is left unchanged; some servers gate on it, but it remains overridable via NetworkConfig.userAgent.

Summary by CodeRabbit

• Bug Fixes

  • Improved image loading through redirects, including better handling of cookies so redirected requests resolve more reliably.
  • Fixed redirect behavior so requests can complete within the expected redirect limit without looping unnecessarily.

• Tests

  • Added coverage for cookie-based redirects and redirect chains to help prevent regressions.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 66b91037-e997-44b7-9eed-5cf2d5ced672

📥 Commits

Reviewing files that changed from the base of the PR and between 7187dec and 581c124.

📒 Files selected for processing (4)

• gradle/libs.versions.toml
• landscapist-core/build.gradle.kts
• landscapist-core/src/commonMain/kotlin/com/skydoves/landscapist/core/network/KtorImageFetcher.kt
• landscapist-core/src/commonTest/kotlin/com/skydoves/landscapist/core/network/KtorImageFetcherTest.kt

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Walkthrough

The Ktor client configuration in KtorImageFetcher is refactored into a reusable extension that installs HttpCookies for cross-redirect cookie persistence and increases HttpSend's maxSendCount to maxRedirects + 1. A ktor-mock test dependency and a new test suite validate redirect and cookie handling.

Changes

Ktor redirect and cookie fix

Layer / File(s)	Summary
HttpClient configuration with cookie support landscapist-core/src/commonMain/kotlin/com/skydoves/landscapist/core/network/KtorImageFetcher.kt	Extracts client setup into an internal configureForImageLoading extension, installs HttpCookies, and changes maxSendCount from maxRedirects to maxRedirects + 1.
Test dependency and redirect/cookie test suite gradle/libs.versions.toml, landscapist-core/build.gradle.kts, landscapist-core/src/commonTest/kotlin/com/skydoves/landscapist/core/network/KtorImageFetcherTest.kt	Adds a ktor-mock library entry and test dependency, and introduces KtorImageFetcherTest with tests for cookie-gated redirects, redirect chains within limits, and chains exceeding maxRedirects.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Possibly related PRs

• skydoves/landscapist#860: Both PRs modify KtorImageFetcher.kt's Ktor HttpClient redirect handling by configuring HttpSend's max send/redirect count.

Sequence Diagram(s)

sequenceDiagram
  participant Client
  participant KtorImageFetcher
  participant HttpClient
  participant Server
  Client->>KtorImageFetcher: fetch(url)
  KtorImageFetcher->>HttpClient: create() with configureForImageLoading
  HttpClient->>Server: initial request
  Server-->>HttpClient: redirect + Set-Cookie
  HttpClient->>HttpClient: persist cookie (HttpCookies)
  HttpClient->>Server: retry with cookie (maxSendCount = maxRedirects + 1)
  Server-->>HttpClient: image bytes
  HttpClient-->>KtorImageFetcher: FetchResult
  KtorImageFetcher-->>Client: image bytes

Loading

Poem

A redirect once looped and looped in vain,
Twenty tries, then failure's stinging pain.
Now cookies stick, one hop more we allow,
The bunny hops through — image loads right now! 🐇
Hooray, no more chasing my own tail! 🥕

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/859-redirect-cookie-loop

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