Merge pull request #2958 from jozanek/issue-1357-quiet-meta-build-export

Change-detect and quiet the automatic sbt meta-build export

Author: tgodzik

docs/build-tools/sbt.md

@@ -261,5 +261,32 @@ either you or an sbt plugin are incremental and complete as soon as possible.
 Lastly, make sure you keep a hot sbt session around as much time as possible. Running `bloopInstall`
 a second time in the sbt session is *really* fast.
 
+### Export the sbt meta-build
+
+Bloop can also export the sbt **meta-build** (the build definition under `project/`) so that Metals
+and similar tools can compile and navigate your `project/*.scala` and `*.sbt` sources. This is
+**opt-in** — a plain `sbt` session does not export the meta-build, so startup stays fast and quiet.
+
+Enable it with the `bloop.export-meta-build` system property or the `BLOOP_EXPORT_META_BUILD`
+environment variable. These are read at every meta-build layer, so they also cover nested
+`project/project` builds:
+
+```bash
+sbt -Dbloop.export-meta-build=true
+# or
+BLOOP_EXPORT_META_BUILD=true sbt
+```
+
+Metals sets this automatically when it runs `bloopInstall`, so meta-build navigation works there
+without any extra configuration.
+
+You can also enable it from the build with the `bloopExportMetaBuild` setting, but it only affects the
+layer it is defined in (`project/*.sbt` configures the outer meta-build, `project/project/*.sbt` the
+next one down), so for nested meta-builds prefer the property or environment variable above:
+
+```scala
+Global / bloopExportMetaBuild := true
+```
+
 [sbt-configuration]: https://www.scala-sbt.org/1.x/docs/Multi-Project.html
 [integration-test-conf]: https://www.scala-sbt.org/1.0/docs/offline/Testing.html#Integration+Tests

integrations/sbt-bloop/src/main/scala/bloop/integrations/sbt/SbtBloop.scala

@@ -64,6 +64,8 @@ object BloopKeys {
     settingKey[File]("Directory where to write bloop configuration files")
   val bloopIsMetaBuild: SettingKey[Boolean] =
     settingKey[Boolean]("Is this a meta build?")
+  val bloopExportMetaBuild: SettingKey[Boolean] =
+    settingKey[Boolean]("Automatically export the sbt meta-build on load (needed by Metals).")
   val bloopAggregateSourceDependencies: SettingKey[Boolean] =
     settingKey[Boolean]("Flag to tell bloop to aggregate bloop config files in the same bloop dir")
   val bloopExportJarClassifiers: SettingKey[Option[Set[String]]] =
@@ -151,6 +153,11 @@ object BloopDefaults {
         .map(_.split(",").toSet)
         .orElse(Some(Set("sources")))
     },
+    BloopKeys.bloopExportMetaBuild := {
+      Option(System.getProperty("bloop.export-meta-build"))
+        .orElse(Option(System.getenv("BLOOP_EXPORT_META_BUILD")))
+        .contains("true")
+    },
     BloopKeys.bloopInstall := bloopInstall.value,
     BloopKeys.bloopAggregateSourceDependencies := true,
     // Override classifiers so that we don't resolve always docs
@@ -167,10 +174,11 @@ object BloopDefaults {
     },
     Keys.onLoad := {
       val oldOnLoad = Keys.onLoad.value
+      val isMetaBuild = BloopKeys.bloopIsMetaBuild.value
+      val exportMetaBuild = BloopKeys.bloopExportMetaBuild.value
       oldOnLoad.andThen { state =>
-        val isMetaBuild = BloopKeys.bloopIsMetaBuild.value
-        if (!isMetaBuild) state
-        else runCommandAndRemaining("bloopInstall")(state)
+        if (isMetaBuild && exportMetaBuild) runCommandAndRemaining("bloopInstall")(state)
+        else state
       }
     },
     BloopKeys.bloopSupportedConfigurations := List(

integrations/sbt-bloop/src/sbt-test/sbt-bloop/meta-builds-export-opt-in/build.sbt

@@ -0,0 +1,29 @@
+val foo = project.in(file("."))
+
+def bloopJsons(dir: File): Seq[File] =
+  Option(dir.listFiles()).toList.flatten.filter { f =>
+    f.isFile && f.getName.endsWith(".json") && f.getName != "bloop.settings.json"
+  }
+
+val metaBloopDir = settingKey[File]("Outer meta-build .bloop dir")
+metaBloopDir := (ThisBuild / baseDirectory).value / "project" / ".bloop"
+
+val metaMetaBloopDir = settingKey[File]("Nested meta-build .bloop dir")
+metaMetaBloopDir := (ThisBuild / baseDirectory).value / "project" / "project" / ".bloop"
+
+val checkExportsAbsent = taskKey[Unit]("Assert neither meta-build layer was exported")
+checkExportsAbsent := {
+  val meta = bloopJsons(metaBloopDir.value)
+  val metaMeta = bloopJsons(metaMetaBloopDir.value)
+  assert(meta.isEmpty, s"Expected no outer meta-build export, found: $meta")
+  assert(metaMeta.isEmpty, s"Expected no nested meta-build export, found: $metaMeta")
+}
+
+val checkExportsPresent = taskKey[Unit]("Assert both meta-build layers were exported")
+checkExportsPresent := {
+  assert(bloopJsons(metaBloopDir.value).nonEmpty, "Expected the outer meta-build to be exported")
+  assert(
+    bloopJsons(metaMetaBloopDir.value).nonEmpty,
+    "Expected the nested meta-build to be exported"
+  )
+}

integrations/sbt-bloop/src/sbt-test/sbt-bloop/meta-builds-export-opt-in/changes/export-meta.sbt

@@ -0,0 +1 @@
+Global / bloopExportMetaBuild := true

integrations/sbt-bloop/src/sbt-test/sbt-bloop/meta-builds-export-opt-in/project/plugins.sbt

@@ -0,0 +1 @@
+addSbtPlugin("ch.epfl.scala" % "sbt-bloop" % sys.props.apply("plugin.version"))

integrations/sbt-bloop/src/sbt-test/sbt-bloop/meta-builds-export-opt-in/project/project/plugins.sbt

@@ -0,0 +1 @@
+addSbtPlugin("ch.epfl.scala" % "sbt-bloop" % sys.props.apply("plugin.version"))

integrations/sbt-bloop/src/sbt-test/sbt-bloop/meta-builds-export-opt-in/project/project/project/plugins.sbt

@@ -0,0 +1 @@
+addSbtPlugin("ch.epfl.scala" % "sbt-bloop" % sys.props.apply("plugin.version"))

integrations/sbt-bloop/src/sbt-test/sbt-bloop/meta-builds-export-opt-in/test

@@ -0,0 +1,8 @@
+# The meta-build export is opt-in: a default load exports neither meta-build layer.
+> checkExportsAbsent
+# Opt in at both the outer (project/) and nested (project/project/) layers, reload,
+# and both must now export.
+$ copy-file changes/export-meta.sbt project/export-meta.sbt
+$ copy-file changes/export-meta.sbt project/project/export-meta.sbt
+> reload
+> checkExportsPresent

integrations/sbt-bloop/src/sbt-test/sbt-bloop/meta-builds/project/export-meta.sbt

@@ -0,0 +1,2 @@
+// The meta-build export is opt-in; enable it so this test exercises the export.
+Global / bloopExportMetaBuild := true