PoC of using gradle to obtain classpath for dependency expressed in config

[ktoso]

PoC of the necessary infra for https://github.com/swiftlang/swift-java/issues/135

Brought the PoC to a place where I can leave it for a moment before I get back to it.

This allows us to: use gradle as an API to resolve and fetch dependencies, and return a classpath containing them.

Usage like this:

swift run Java2Swift --module-name JavaJacksonDatabind --fetch \
  --cp ./JavaKit/build/classes/java/main/:/Users/ktoso/.gradle/caches/modules-2/files-2.1/dev.gradleplugins/gradle-api/8.10.1/a236c4ed58ea4234cef8217bf8dc0793a02d80be/gradle-api-8.10.1.jar:... \
Samples/JavaDependenciesApp/Sources/JavaJacksonDatabind/Java2Swift.config

Problems to solve:

• bootstraping, the initial run of such must fetch the gradle API, and we don't yet have the gradle API to fetch it... We probably should have a mini project with the gradle dependency somewhere, build it and get the classpath from there. Store it, and then keep using it for those "fetch" invocations.
• SwiftPM integration, we could just automatically fetch dependencies when encountered.
• We should probably also allow "point at existing build.gradle file" mode, which would be very useful in real projects where there's likely a gradle project already. This way developers can open "the java project" and open "the swift project" and both would be in sync.

[ktoso]

For reference, here's output for fetching gradle-api:

This showcases mostly how quickly very large those dependency trees can become. And basically we can take that classpath and feed it into our other tool invocations as additional path - getting us out of jar-hell 👍

FETCH DEPENDENCIES FOR: [dev.gradleplugins:gradle-api:8.10.1]

RESOLVED CLASSPATH: /private/var/folders/hn/c22y4jsn4j74mw23_kpgn88w0000gn/T/java-swift-dependencies4361964387107219063/build/classes/java/main:/private/var/folders/hn/c22y4jsn4j74mw23_kpgn88w0000gn/T/java-swift-dependencies4361964387107219063/build/resources/main:/Users/ktoso/.gradle/caches/modules-2/files-2.1/dev.gradleplugins/gradle-api/8.10.1/a236c4ed58ea4234cef8217bf8dc0793a02d80be/gradle-api-8.10.1.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/org.codehaus.groovy/groovy-all/3.0.22/eef9a93f08c895cba735c6aed28e9ce32b762229/groovy-all-3.0.22.pom:/Users/ktoso/.gradle/caches/modules-2/files-2.1/org.jetbrains.kotlin/kotlin-stdlib/1.9.24/9928532f12c66ad816a625b3f9984f8368ca6d2b/kotlin-stdlib-1.9.24.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/org.codehaus.groovy/groovy-ant/3.0.22/b90ebe5f97170162105fa87b3e69f8a51f2ef6ea/groovy-ant-3.0.22.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/org.codehaus.groovy/groovy-astbuilder/3.0.22/ad926cd4b93271af8181899c360d93b380d5a9e/groovy-astbuilder-3.0.22.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/org.codehaus.groovy/groovy-cli-picocli/3.0.22/94f33323a1779cb89b1faea54beea4670bd42c40/groovy-cli-picocli-3.0.22.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/org.codehaus.groovy/groovy-groovysh/3.0.22/70f050713a499e0ecd79b3c49b80b9d4d35041f1/groovy-groovysh-3.0.22.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/org.codehaus.groovy/groovy-console/3.0.22/14875d49eb557088303c04b7c91ce66589608c44/groovy-console-3.0.22.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/org.codehaus.groovy/groovy-datetime/3.0.22/bae704f1f7a2b80b9b9b00071e0cedb480688149/groovy-datetime-3.0.22.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/org.codehaus.groovy/groovy-groovydoc/3.0.22/6cebde157f06db0629b67545f87775232462ced1/groovy-groovydoc-3.0.22.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/org.codehaus.groovy/groovy-docgenerator/3.0.22/e52b0f06a811ba503c19cb0c6a269498baf6830f/groovy-docgenerator-3.0.22.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/org.codehaus.groovy/groovy-jmx/3.0.22/caa285ee1a15b08a5f113ca3183fc91622072fda/groovy-jmx-3.0.22.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/org.codehaus.groovy/groovy-json/3.0.22/28e337f52b31cc890ad4eb51e738a2bce47a3f1c/groovy-json-3.0.22.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/org.codehaus.groovy/groovy-jsr223/3.0.22/60ea08d95ac160f06d7065cbd37d6548ca665eb/groovy-jsr223-3.0.22.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/org.codehaus.groovy/groovy-macro/3.0.22/a66f5cf47799eceae07ab7431ad0aaf3e1b7ed3f/groovy-macro-3.0.22.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/org.codehaus.groovy/groovy-nio/3.0.22/7b3f5ac7421efec8efd1b0c7064bcb4b68379e4c/groovy-nio-3.0.22.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/org.codehaus.groovy/groovy-servlet/3.0.22/71bb16ddcc8155de17bc343174f2b5348dda101c/groovy-servlet-3.0.22.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/org.codehaus.groovy/groovy-sql/3.0.22/8a208e8eb1156f4f27aa5dfa102f25420560ce83/groovy-sql-3.0.22.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/org.codehaus.groovy/groovy-swing/3.0.22/a96b8203c71923c1b6343d4bbdc36ba973307d74/groovy-swing-3.0.22.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/org.codehaus.groovy/groovy-templates/3.0.22/c8cf8e0bb82d7e112e87c6492b17f62da267b8ec/groovy-templates-3.0.22.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/org.codehaus.groovy/groovy-test/3.0.22/cc61e98fe6eba4f29aed40a1ed1fda601a0e84eb/groovy-test-3.0.22.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/org.codehaus.groovy/groovy-test-junit5/3.0.22/663cbadeb7c42bf1e11d7f9a01e3d8ddb0d5eb77/groovy-test-junit5-3.0.22.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/org.codehaus.groovy/groovy-testng/3.0.22/2964eb7933377694db6cfa321ca7a2d16f29fc81/groovy-testng-3.0.22.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/org.codehaus.groovy/groovy-xml/3.0.22/de0dd2f84c3befb280132866d0a6bf3ae031f55a/groovy-xml-3.0.22.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/org.codehaus.groovy/groovy/3.0.22/8403cbf38ed86f9fde3abbf0d2548642ddfebd00/groovy-3.0.22.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/org.jetbrains/annotations/13.0/919f0dfe192fb4e063e7dacadee7f8bb9a2672a9/annotations-13.0.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/org.apache.ant/ant-junit/1.10.14/e5f7b5a367cb03a73879018331c7065a2a479954/ant-junit-1.10.14.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/org.apache.ant/ant/1.10.14/1edce9bbfa60dfd51f010879c78f4421dafae7a7/ant-1.10.14.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/org.apache.ant/ant-launcher/1.10.14/8d2268288496b0541a2640f2ee07fe3de1a02301/ant-launcher-1.10.14.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/org.apache.ant/ant-antlr/1.10.14/1f19602f622fa9fa04f9aa8807f935b571ca05ca/ant-antlr-1.10.14.jar:/Users/ktoso/.gradle/caches/modules-2/files-2.1/info.picocli/picocli/4.6.3/18177f4c3d65cc94e6d4039775ec5aed8089f8d0/picocli-4.6.3.jar:/Users/ktoso/.gradle/caches/modules-2/file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