Add built-in sitemap generation support for SEO (#701)

[kocheick]

Overview

Implements automatic XML sitemap generation for Kobweb applications to improve SEO and search engine discoverability.

Closes #701

Implementation Details

New Features

• Automatic sitemap generation: Creates sitemap.xml at site root (/sitemap.xml)
• Smart route discovery: Uses existing @Page annotation detection (includes markdown-generated pages)
• Flexible configuration: DSL block under kobweb.app.sitemap { ... }
• Dynamic route filtering: Excludes parameterized routes like /users/{id} by default
• Custom filtering: Support for excludeRoutes, extraRoutes, and custom routeFilter lambdas
• Localhost testing: Supports http://localhost:8080 for development testing
• Standards compliant: Generates proper XML sitemaps following sitemaps.org specification

Task Dependencies

• Runs after markdown processing (kobwebxMarkdownProcess) when present
• Integrated into resource processing pipeline
• Outputs directly to src/jsMain/resources/public/sitemap.xml

Configuration Examples

Basic usage:

kobweb {
    app {
        sitemap {
            baseUrl.set("https://mysite.com")
        }
    }
}

Advanced configuration:

kobweb {
    app {
        sitemap {
            baseUrl.set("https://mysite.com")
            extraRoutes.addAll("/blog/post-1", "/products/special")
            excludeRoutes.addAll("/admin", "/internal")
            routeFilter.set { !it.contains("/temp/") }
        }
    }
}

Localhost testing:

kobweb {
    app {
        sitemap {
            baseUrl.set("http://localhost:8080")
        }
    }
}

Key Benefits

• Zero configuration: Works out-of-the-box for most sites with just baseUrl
• Markdown integration: Automatically includes markdown-generated pages
• Development friendly: Easy to test locally with localhost URLs
• Production ready: Handles large sites with size limit warnings
• SEO optimized: Places sitemap at standard /sitemap.xml location

Files Added/Modified

• New: KobwebGenerateSitemapTask.kt - Main sitemap generation task
• Modified: AppBlock.kt - Added SitemapBlock configuration DSL
• Modified: KobwebApplicationPlugin.kt - Task registration and dependency wiring

Testing

• Supports http://localhost:8080 for local development testing
• Generates sitemap at src/jsMain/resources/public/sitemap.xml
• Accessible at /sitemap.xml when server is running
• Works with both development (kobweb start) and production (kobweb export) workflows

Breaking Changes

None - this is purely additive functionality that only activates when baseUrl is configured.

[DennisTsar]

Thanks for your work on this.

I took a look at the code relating to the task creation & configuration and left some comments/tips about how to make it more Gradle idiomatic. I haven't looked at the code the pertains to the actual sitemap generation.

The biggest thing to address is the following (copied from one my comments below):

It's worth considering how we actually want a user to enable/disable sitemap generation. While onlyIf { baseUrl.isPresent } is an option, it has a few drawbacks:

• It's not obvious to a user that baseUrl is required for sitemap generation
• Users that don't want sitemap generation still see the (skipped) task in their console

Instead, I would suggest having sitemap generation enabled with a function:

fun generateSitemap(baseUrl: String, /* other parameters with defaults */)
// or possibly
fun generateSitemap(baseUrl: String, config: SitemapConfig.() -> Unit = {})

The latter could be nicer to support Property values, which would allow creating a task to, for example, fetch entries from a database, and then use those values to populate extraRoutes for dynamic routes. We could also provide both. Calling the function would register the sitemap generation task (with some mechanism to disallow/warn about calling it multiple times) and configure it accordingly.

[DennisTsar]

I'm not sure if you are waiting for a review on this (feel free to request a re-review from me if so), but I'll note that in the current state kobweb run does not work in the playground project (I think due to a misplaced }).

Also, in case it got buried, I described here how to deal with @get:Internal // Avoid serialization issues with lambdas.

[kocheick]

I'm not sure if you are waiting for a review on this (feel free to request a re-review from me if so), but I'll note that in the current state kobweb run does not work in the playground project (I think due to a misplaced }).

Also, in case it got buried, I described here how to deal with @get:Internal // Avoid serialization issues with lambdas.

there was indeed a misplaced }, in the KobwebApplicationPlugin I accidently removed a brace } , puting the jvm Block into the js Block, but now it's fixed.
This has been a great learning experience, because the filterBlock is finally working consistently whenever I change something in the block, however it lead to updating kobwebSiteRoutes
from:

val Project.kobwebSiteRoutes: Provider<List<String>>
    get() = tasks.named<KobwebCacheAppFrontendDataTask>("kobwebCacheAppFrontendData").map { task ->
        val pageEntries =
            Json.decodeFromString<AppFrontendData>(task.appDataFile.get().asFile.readText()).frontendData.pages
        pageEntries
            .asSequence()
            .map { it.route }
            .sorted()
            .toList()
    }

to:

val Project.kobwebSiteRoutes: Provider<List<String>>
    get() = tasks.named<KobwebCacheAppFrontendDataTask>("kobwebCacheAppFrontendData").flatMap { task ->
        task.appDataFile.map { file ->
            val pageEntries =
                Json.decodeFromString<AppFrontendData>(file.asFile.readText()).frontendData.pages
            pageEntries
                .asSequence()
                .map { it.route }
                .sorted()
                .toList()
        }
    }

[kocheick]

regarding kobwebSiteRoutes

Fix: configuration cache compatibility for kobwebSiteRoutes

TL;DR

• Stop reading task outputs during configuration.
• Switch from map + get() to flatMap + map so file I/O happens at execution time.
• Enables Gradle configuration cache and removes intermittent file-missing errors after clean.

Problem

We saw failures like:

.../build/kobweb/cache/kobwebCacheAppFrontendData/appData.json (No such file or directory)

This occurred while Gradle was serializing the configuration cache. Root cause: kobwebSiteRoutes read a task output
file during configuration.

Before (problematic)

val Project.kobwebSiteRoutes: Provider<List<String>>
    get() = tasks.named<KobwebCacheAppFrontendDataTask>("kobwebCacheAppFrontendData").map { task ->
        val pageEntries =
            Json.decodeFromString<AppFrontendData>(task.appDataFile.get().asFile.readText()).frontendData.pages
        pageEntries.asSequence().map { it.route }.sorted().toList()
    }

• task.appDataFile.get() forces eager resolution at configuration time.
• File often doesn’t exist yet; also breaks config cache constraints.

After (config-cache friendly)

val Project.kobwebSiteRoutes: Provider<List<String>>
    get() = tasks.named<KobwebCacheAppFrontendDataTask>("kobwebCacheAppFrontendData").flatMap { task ->
        task.appDataFile.map { file ->
            val pageEntries =
                Json.decodeFromString<AppFrontendData>(file.asFile.readText()).frontendData.pages
            pageEntries.asSequence().map { it.route }.sorted().toList()
        }
    }

• flatMap defers resolving appDataFile until execution.
• Inner map defers file I/O until the provider is realized by a task.
• No .get() during configuration.

Why this change

• Preserve API: still returns Provider<List<String>> with the same behavior.
• Align with Gradle provider best practices (no eager .get() in configuration phase).
• Unblock configuration cache for faster subsequent builds.
• Remove flakiness after clean when the file hasn’t been produced yet.

Impact

• Functional: no changes for consumers of kobwebSiteRoutes (sitemap, route tools, etc.).
• Performance: configuration cache usable; faster repeat builds.
• Stability: eliminates intermittent file-missing errors.

Verification

• ./gradlew clean kobwebStart: passes.
• Subsequent runs reuse configuration cache without errors.
• Features depending on kobwebSiteRoutes (e.g., sitemap) behave as before.

Follow-ups / guidance

• Avoid .get() on Property/Provider during configuration.
• Prefer provider chains:
  • Avoid: provider.map { it.output.get().asFile.readText() }
  • Prefer: provider.flatMap { it.output.map { file -> file.asFile.readText() } }
• For onlyIf guards, capture simple booleans at configuration time instead of touching task outputs or extensions at
  execution time.