Don't migrate directives with fix for single-file projects

modules/cli/src/main/scala/scala/cli/commands/fix/BuiltInRules.scala

@@ -39,6 +39,26 @@ object BuiltInRules extends CommandHelpers {
       .left.map(CompositeBuildException(_))
       .orExit(logger)
 
+    val sourcesCount =
+      mainSources.paths.length + mainSources.inMemory.length +
+        testSources.paths.length + testSources.inMemory.length
+    sourcesCount match
+      case 0 =>
+        logger.message("No sources to migrate directives from.")
+        logger.message("Nothing to do.")
+      case 1 =>
+        logger.message("No need to migrate directives for a single source file project.")
+        logger.message("Nothing to do.")
+      case _ => migrateDirectives(inputs, buildOptions, mainSources, testSources, logger)
+  }
+
+  private def migrateDirectives(
+    inputs: Inputs,
+    buildOptions: BuildOptions,
+    mainSources: Sources,
+    testSources: Sources,
+    logger: Logger
+  )(using ScalaCliInvokeData): Unit = {
     // Only initial inputs are used, new inputs discovered during processing of
     // CrossSources.forInput may be shared between projects
     val writableInputs: Seq[OnDisk] = inputs.flattened()
@@ -120,8 +140,8 @@ object BuiltInRules extends CommandHelpers {
     directivesFromWritableTestInputs
       .filterNot(ttd => isProjectFile(ttd.positions))
       .foreach(ttd => removeDirectivesFrom(ttd.positions, toKeep = ttd.noTestPrefixAvailable))
-
   }
+
   private def getProjectSources(inputs: Inputs, logger: Logger)(using
     ScalaCliInvokeData
   ): Either[::[BuildException], (Sources, Sources)] = {

modules/integration/src/test/scala/scala/cli/integration/FixBuiltInRulesTestDefinitions.scala

@@ -447,4 +447,37 @@ trait FixBuiltInRulesTestDefinitions { _: FixTestDefinitions =>
         expect(r.out.trim() == expectedMessage)
       }
     }
+
+  {
+    val directive = "//> using dep com.lihaoyi::os-lib:0.9.3"
+    for {
+      (inputFileName, code) <- Seq(
+        "raw.scala" -> s"""$directive
+                          |object Main extends App {
+                          |  println(os.pwd)
+                          |}
+                          |""".stripMargin,
+        "script.sc" -> s"""$directive
+                          |println(os.pwd)
+                          |""".stripMargin
+      )
+      testInputs = TestInputs(os.rel / inputFileName -> code)
+    }
+      test(
+        s"dont extract directives into project.scala for a single-file project: $inputFileName"
+      ) {
+        testInputs.fromRoot { root =>
+          val fixResult = os.proc(TestUtil.cli, "--power", "fix", ".", extraOptions)
+            .call(cwd = root, stderr = os.Pipe)
+          expect(fixResult.err.trim().contains(
+            "No need to migrate directives for a single source file project"
+          ))
+          expect(!os.exists(root / projectFileName))
+          expect(os.read(root / inputFileName) == code)
+          val runResult = os.proc(TestUtil.cli, "run", ".", extraOptions)
+            .call(cwd = root, stderr = os.Pipe)
+          expect(runResult.out.trim() == root.toString)
+        }
+      }
+  }
 }

modules/integration/src/test/scala/scala/cli/integration/FixScalafixRulesTestDefinitions.scala

@@ -78,7 +78,8 @@ trait FixScalafixRulesTestDefinitions {
       os.rel / "Hello.scala" -> unusedValueInputsContent
     )
     val expectedContent: String = noCrLf {
-      s"""package foo
+      s"""//> using options $scalafixUnusedRuleOption
+         |package foo
          |
          |object Hello {
          |  def main(args: Array[String]): Unit = {
@@ -88,19 +89,11 @@ trait FixScalafixRulesTestDefinitions {
          |}
          |""".stripMargin
     }
-    val expectedProjectContent: String = noCrLf {
-      s"""// Main
-         |//> using options $scalafixUnusedRuleOption
-         |
-         |""".stripMargin
-    }
 
     semanticRuleInputs.fromRoot { root =>
       os.proc(TestUtil.cli, "fix", "--power", ".", scalaVersionArgs).call(cwd = root)
       val updatedContent = noCrLf(os.read(root / "Hello.scala"))
       expect(updatedContent == expectedContent)
-      val projectContent = noCrLf(os.read(root / "project.scala"))
-      expect(projectContent == expectedProjectContent)
     }
   }
 
@@ -136,9 +129,9 @@ trait FixScalafixRulesTestDefinitions {
         scalaVersionArgs
       ).call(cwd = root)
       val updatedContent = noCrLf(os.read(root / "Hello.scala"))
-      val projectContent = noCrLf(os.read(root / "project.scala"))
       val expected = noCrLf {
-        s"""|package hello
+        s"""|//> using options $scalafixUnusedRuleOption
+            |package hello
             |
             |object Hello {
             |  def a = {
@@ -148,15 +141,8 @@ trait FixScalafixRulesTestDefinitions {
             |}
             |""".stripMargin
       }
-      val expectedProjectContent: String = noCrLf {
-        s"""// Main
-           |//> using options $scalafixUnusedRuleOption
-           |
-           |""".stripMargin
-      }
 
       expect(updatedContent == expected)
-      expect(projectContent == expectedProjectContent)
 
     }
   }
@@ -259,24 +245,18 @@ trait FixScalafixRulesTestDefinitions {
       os.rel / "Hello.scala" -> original
     )
     val expectedContent: String = noCrLf {
-      """|object CollectHeadOptionTest {
-         |  def x1: Option[String] = List(1, 2, 3).collectFirst{ case n if n % 2 == 0 => n.toString }
-         |}
-         |""".stripMargin
-    }
-    val expectedProjectContent: String = noCrLf {
-      s"""// Main
-         |$directive
-         |
-         |""".stripMargin
+      s"""|$directive
+          |
+          |object CollectHeadOptionTest {
+          |  def x1: Option[String] = List(1, 2, 3).collectFirst{ case n if n % 2 == 0 => n.toString }
+          |}
+          |""".stripMargin
     }
 
     inputs.fromRoot { root =>
       os.proc(TestUtil.cli, "fix", ".", "--power", scalaVersionArgs).call(cwd = root)
       val updatedContent = noCrLf(os.read(root / "Hello.scala"))
       expect(updatedContent == expectedContent)
-      val projectContent = noCrLf(os.read(root / "project.scala"))
-      expect(projectContent == expectedProjectContent)
     }
   }
 

website/docs/commands/fix.md

@@ -30,6 +30,8 @@ Files containing (experimental) `using target` directives, e.g. `//> using targe
 The original scope (`main` or `test`) of each extracted directive is respected. `main` scope directives are transformed 
 them into their `test.*` equivalent when needed.
 
+Note: directives won't be extracted for single-file projects.
+
 ## `scalafix` integration
 
 Scala CLI is capable of running [Scalafix](https://scalacenter.github.io/scalafix/) (a refactoring and linting tool for Scala) on your project.