Merge branch 'stdlib-resolution'

Author: fwcd

src/main/kotlin/org/javacs/kt/classpath/findClassPath.kt

@@ -28,10 +28,55 @@ fun findClassPath(workspaceRoots: Collection<Path>): Set<Path> {
 }
 
 private fun ensureStdlibInPaths(paths: Set<Path>): Set<Path> {
-    // Ensure that there is exactly one kotlin-stdlib present
+    // Ensure that there is exactly one kotlin-stdlib present, and/or exactly one of kotlin-stdlib-common, -jdk8, etc.
     val isStdlib: ((Path) -> Boolean) = { it.toString().contains("kotlin-stdlib") }
-    val stdlib = paths.firstOrNull(isStdlib) ?: findKotlinStdlib()
-    return paths.filterNot(isStdlib).union(listOf(stdlib).filterNotNull())
+
+    val linkedStdLibs = paths.filter(isStdlib)
+        .mapNotNull { StdLibItem.from(it) }
+        .groupBy { it.key }
+        .map { candidates ->
+            // For each "kotlin-stdlib-blah", use the newest.  This may not be correct behavior if the project has lots of
+            // conflicting dependencies, but in general should get enough of the stdlib loaded that we can display errors
+            
+            candidates.value.sortedWith(
+                compareByDescending<StdLibItem> { it.major } then
+                    compareByDescending { it.minor } then
+                        compareByDescending { it.patch }
+            ).first().path
+        }
+
+    val stdlibs = if (linkedStdLibs.isNotEmpty()) {
+        linkedStdLibs
+    } else {
+        findKotlinStdlib()?.let { listOf(it) } ?: listOf()
+    }
+
+    return paths.filterNot(isStdlib).union(stdlibs)
+}
+
+private data class StdLibItem(
+    val key : String,
+    val major : Int,
+    val minor: Int,
+    val patch : Int,
+    val path: Path
+) {
+    companion object {
+        // Matches names like: "kotlin-stdlib-jdk7-1.2.51.jar"
+        val parser = Regex("""(kotlin-stdlib(-[^-]+)?)-(\d+)\.(\d+)\.(\d+)\.jar""")
+
+        fun from(path: Path) : StdLibItem? {
+            return parser.matchEntire(path.fileName.toString())?.let { match ->
+                StdLibItem(
+                    key = match.groups[1]?.value ?: match.groups[0]?.value!!,
+                    major = match.groups[3]?.value?.toInt() ?: 0,
+                    minor = match.groups[4]?.value?.toInt() ?: 0,
+                    patch = match.groups[5]?.value?.toInt() ?: 0,
+                    path = path
+                )
+            }
+        }
+    }
 }
 
 private fun backupClassPath() =