From e004fe3874067d743b38d293b5d4d3e4dc2bd658 Mon Sep 17 00:00:00 2001
From: Katarzyna Marek <kasia@marek.net>
Date: Tue, 24 Oct 2023 11:01:46 +0200
Subject: [PATCH] improvement: recompile focused file if depends on last
 compiled bt

---
 .../meta/internal/metals/Compilations.scala   | 12 +++-
 .../internal/metals/MetalsLspService.scala    |  7 ++-
 .../test/scala/tests/DidFocusLspSuite.scala   | 59 ++++++++++++++++++-
 3 files changed, 74 insertions(+), 4 deletions(-)

diff --git a/metals/src/main/scala/scala/meta/internal/metals/Compilations.scala b/metals/src/main/scala/scala/meta/internal/metals/Compilations.scala
index 5889eaad22b..0eabb90d8a5 100644
--- a/metals/src/main/scala/scala/meta/internal/metals/Compilations.scala
+++ b/metals/src/main/scala/scala/meta/internal/metals/Compilations.scala
@@ -91,10 +91,20 @@ final class Compilations(
     } yield result
   }
 
-  def compileFiles(paths: Seq[AbsolutePath]): Future[Unit] = {
+  def compileFiles(
+      paths: Seq[AbsolutePath],
+      focusedDocumentBuildTarget: Option[BuildTargetIdentifier],
+  ): Future[Unit] = {
     for {
       targets <- expand(paths)
       _ <- compileBatch(targets)
+      _ <- focusedDocumentBuildTarget match {
+        case Some(bt)
+            if !targets.contains(bt) &&
+              buildTargets.isInverseDependency(bt, targets.toList) =>
+          compileBatch(bt)
+        case _ => Future.successful(())
+      }
       _ <- compileWorksheets(paths)
     } yield ()
   }
diff --git a/metals/src/main/scala/scala/meta/internal/metals/MetalsLspService.scala b/metals/src/main/scala/scala/meta/internal/metals/MetalsLspService.scala
index 8ba4ebc850d..86faa1bfe9b 100644
--- a/metals/src/main/scala/scala/meta/internal/metals/MetalsLspService.scala
+++ b/metals/src/main/scala/scala/meta/internal/metals/MetalsLspService.scala
@@ -1330,11 +1330,13 @@ class MetalsLspService(
     paths.foreach { path =>
       fingerprints.add(path, FileIO.slurp(path, charset))
     }
+
     Future
       .sequence(
         List(
           Future(indexer.reindexWorkspaceSources(paths)),
-          compilations.compileFiles(paths),
+          compilations
+            .compileFiles(paths, Option(focusedDocumentBuildTarget.get())),
           onBuildChanged(paths).ignoreValue,
           Future.sequence(paths.map(onBuildToolAdded)),
         ) ++ paths.map(f => Future(interactiveSemanticdbs.textDocument(f)))
@@ -1346,7 +1348,8 @@ class MetalsLspService(
     Future
       .sequence(
         List(
-          compilations.compileFiles(List(path)),
+          compilations
+            .compileFiles(List(path), Option(focusedDocumentBuildTarget.get())),
           Future {
             diagnostics.didDelete(path)
             testProvider.onFileDelete(path)
diff --git a/tests/unit/src/test/scala/tests/DidFocusLspSuite.scala b/tests/unit/src/test/scala/tests/DidFocusLspSuite.scala
index 830e7564334..73767cae753 100644
--- a/tests/unit/src/test/scala/tests/DidFocusLspSuite.scala
+++ b/tests/unit/src/test/scala/tests/DidFocusLspSuite.scala
@@ -21,7 +21,8 @@ class DidFocusLspSuite extends BaseLspSuite("did-focus") {
           |  "a": {},
           |  "b": {
           |    "dependsOn": ["a"]
-          |  }
+          |  },
+          |  "c": {}
           |}
           |/a/src/main/scala/a/A.scala
           |package a
@@ -38,6 +39,11 @@ class DidFocusLspSuite extends BaseLspSuite("did-focus") {
           |object C {
           |  val z: Int = a.A.x
           |}
+          |/c/src/main/scala/c/C.scala
+          |package c
+          |object E {
+          | val i: Int = "aaa"
+          |}
         """.stripMargin
       )
       _ <- server.didOpen("a/src/main/scala/a/A.scala")
@@ -48,6 +54,7 @@ class DidFocusLspSuite extends BaseLspSuite("did-focus") {
       _ = assert(didCompile == AlreadyCompiled)
       didCompile <- server.didFocus("b/src/main/scala/b/B.scala")
       _ = assert(didCompile == AlreadyCompiled)
+      didCompile <- server.didFocus("c/src/main/scala/c/C.scala")
       _ <- server.didSave("a/src/main/scala/a/A.scala")(
         _.replace("val x = 1", "val x = \"string\"")
       )
@@ -68,6 +75,56 @@ class DidFocusLspSuite extends BaseLspSuite("did-focus") {
       )
     } yield ()
   }
+
+  test("compiled-focused") {
+    cleanWorkspace()
+    for {
+      _ <- initialize(
+        """
+          |/metals.json
+          |{
+          |  "a": {},
+          |  "b": {
+          |    "dependsOn": ["a"]
+          |  }
+          |}
+          |/a/src/main/scala/a/A.scala
+          |package a
+          |object A {
+          |  val x = 1
+          |}
+          |/a/src/main/scala/a/A2.scala
+          |package a
+          |object A2 {
+          |  val y = 1
+          |}
+          |/b/src/main/scala/b/B.scala
+          |package b
+          |object C {
+          |  val z: Int = a.A.x
+          |}
+        """.stripMargin
+      )
+      _ <- server.didOpen("a/src/main/scala/a/A.scala")
+      _ <- server.didOpen("b/src/main/scala/b/B.scala")
+      _ = assertNoDiagnostics()
+      _ = fakeTime.elapseSeconds(10)
+      didCompile <- server.didFocus("b/src/main/scala/b/B.scala")
+      _ <- server.didSave("a/src/main/scala/a/A.scala")(
+        _.replace("val x = 1", "val x = \"string\"")
+      )
+      _ = fakeTime.elapseSeconds(10)
+      _ = assertNoDiff(
+        client.workspaceDiagnostics,
+        """|b/src/main/scala/b/B.scala:3:16: error: type mismatch;
+           | found   : String
+           | required: Int
+           |  val z: Int = a.A.x
+           |               ^^^^^
+           |""".stripMargin,
+      )
+    } yield ()
+  }
 }
 
 // https://github.com/scalameta/metals/issues/497