Generate documentation from TASTY in sbt plugin

compiler/src/dotty/tools/dotc/Driver.scala

@@ -61,7 +61,7 @@ class Driver {
   }
 
   /** Setup extra classpath and figure out class names for tasty file inputs */
-  private def fromTastySetup(fileNames0: List[String], ctx0: Context) = {
+  protected def fromTastySetup(fileNames0: List[String], ctx0: Context): (List[String], Context) = {
     if (ctx0.settings.fromTasty.value(ctx0)) {
       // Resolve classpath and class names of tasty files
       val (classPaths, classNames) = fileNames0.map { name =>

doc-tool/src/dotty/tools/dottydoc/DocDriver.scala

@@ -27,7 +27,7 @@ class DocDriver extends Driver {
     ctx.setProperty(ContextDoc, new ContextDottydoc)
 
     val fileNames = CompilerCommand.checkUsage(summary, sourcesRequired)(ctx)
-    (fileNames, ctx)
+    fromTastySetup(fileNames, ctx)
   }
 
   override def newCompiler(implicit ctx: Context): Compiler = new DocCompiler

sbt-bridge/src/xsbt/ScaladocInterface.scala

@@ -6,6 +6,7 @@ package xsbt
 import xsbti.{ Logger, Severity }
 import java.net.URL
 import java.util.Optional
+import java.nio.file.{Files, Paths}
 
 import dotty.tools.dotc.core.Contexts.{ Context, ContextBase }
 import dotty.tools.dotc.reporting.Reporter
@@ -16,9 +17,21 @@ class ScaladocInterface {
   }
 }
 
-class DottydocRunner(args: Array[String], log: Logger, delegate: xsbti.Reporter) {
+class DottydocRunner(args0: Array[String], log: Logger, delegate: xsbti.Reporter) {
   def run(): Unit = {
-    log.debug(() => args.mkString("Calling Dottydoc with arguments  (ScaladocInterface):\n\t", "\n\t", ""))
+    log.debug(() => args0.mkString("Calling Dottydoc with arguments  (ScaladocInterface):\n\t", "\n\t", ""))
+
+    val args = {
+      // When running with `-from-tasty`, remove the source files from arg list.
+      if (args0.contains("-from-tasty")) {
+        val (excluded, retained) =
+          args0.partition { arg =>
+            (arg.endsWith(".scala") || arg.endsWith(".java")) && Files.exists(Paths.get(arg))
+          }
+        log.debug(() => excluded.mkString("Running `-from-tasty`, excluding source files:\n\t", "\n\t", ""))
+        retained
+      } else args0
+    }
 
     val ctx = (new ContextBase).initialCtx.fresh
       .setReporter(new DelegatingReporter(delegate))

sbt-dotty/src/dotty/tools/sbtplugin/DottyPlugin.scala

@@ -216,9 +216,19 @@ object DottyPlugin extends AutoPlugin {
           old.withCircularDependencyLevel(sbt.librarymanagement.ivy.CircularDependencyLevel.Ignore)
         } else old
       }
-    )
+    ) ++ inConfig(Compile)(docSettings) ++ inConfig(Test)(docSettings)
   }
 
+  private val docSettings = inTask(doc)(Seq(
+    sources := {
+      val _ = compile.value // Ensure that everything is compiled, so TASTy is available.
+      val prev = sources.value
+      val tastyFiles = (classDirectory.value ** "*.tasty").get.map(_.getAbsoluteFile)
+      prev ++ tastyFiles
+    },
+    scalacOptions += "-from-tasty"
+  ))
+
   /** Fetch artefacts for scalaOrganization.value %% moduleName % scalaVersion.value */
   private def fetchArtifactsOf(moduleName: String) = Def.task {
     val dependencyResolution = Keys.dependencyResolution.value