Fix macro suspensions breaking coverage

Author: jchyb

compiler/src/dotty/tools/dotc/core/Contexts.scala

@@ -982,6 +982,11 @@ object Contexts {
     /** Was best effort file used during compilation? */
     private[core] var usedBestEffortTasty = false
 
+    /** Counter to assign a unique id to each statement (for coverage) */
+    private[dotc] var coverageStatementId = 0
+    /** A variable denoting if the coverage file already written to (for coverage) */
+    private[dotc] var coverageStartedWriting = false
+
     // Types state
     /** A table for hash consing unique types */
     private[core] val uniques: Uniques = Uniques()

compiler/src/dotty/tools/dotc/coverage/Serializer.scala

@@ -1,10 +1,11 @@
 package dotty.tools.dotc
 package coverage
 
-import java.nio.file.{Path, Paths, Files}
+import java.nio.file.{Path, Paths, Files, StandardOpenOption}
 import java.io.Writer
 import scala.language.unsafeNulls
 import scala.collection.mutable.StringBuilder
+import dotty.tools.dotc.core.Contexts.Context
 
 /**
  * Serializes scoverage data.
@@ -16,20 +17,20 @@ object Serializer:
   private val CoverageDataFormatVersion = "3.0"
 
   /** Write out coverage data to the given data directory, using the default coverage filename */
-  def serialize(coverage: Coverage, dataDir: String, sourceRoot: String): Unit =
+  def serialize(coverage: Coverage, dataDir: String, sourceRoot: String)(using Context): Unit =
     serialize(coverage, Paths.get(dataDir, CoverageFileName).toAbsolutePath, Paths.get(sourceRoot).toAbsolutePath)
 
   /** Write out coverage data to a file. */
-  def serialize(coverage: Coverage, file: Path, sourceRoot: Path): Unit =
-    val writer = Files.newBufferedWriter(file)
+  def serialize(coverage: Coverage, file: Path, sourceRoot: Path)(using Context): Unit =
+    val writer = Files.newBufferedWriter(file, StandardOpenOption.CREATE, StandardOpenOption.APPEND)
     try
       serialize(coverage, writer, sourceRoot)
     finally
       writer.close()
 
   /** Write out coverage data (info about each statement that can be covered) to a writer.
    */
-  def serialize(coverage: Coverage, writer: Writer, sourceRoot: Path): Unit =
+  def serialize(coverage: Coverage, writer: Writer, sourceRoot: Path)(using ctx: Context): Unit =
 
     def getRelativePath(filePath: Path): String =
       // We need to normalize the path here because the relativizing paths containing '.' or '..' differs between Java versions
@@ -81,7 +82,8 @@ object Serializer:
                       |\f
                       |""".stripMargin)
 
-    writeHeader(writer)
+    if (!ctx.base.coverageStartedWriting) writeHeader(writer)
+    ctx.base.coverageStartedWriting = true
     coverage.statements.toSeq
       .sortBy(_.id)
       .foreach(stmt => writeStatement(stmt, writer))

compiler/src/dotty/tools/dotc/transform/InstrumentCoverage.scala

@@ -38,9 +38,6 @@ class InstrumentCoverage extends MacroTransform with IdentityDenotTransformer:
   override def isEnabled(using ctx: Context) =
     ctx.settings.coverageOutputDir.value.nonEmpty
 
-  // counter to assign a unique id to each statement
-  private var statementId = 0
-
   // stores all instrumented statements
   private val coverage = Coverage()
 
@@ -54,7 +51,7 @@ class InstrumentCoverage extends MacroTransform with IdentityDenotTransformer:
     val dataDir = File(outputPath)
     val newlyCreated = dataDir.mkdirs()
 
-    if !newlyCreated then
+    if !newlyCreated && !ctx.base.coverageStartedWriting then
       // If the directory existed before, let's clean it up.
       dataDir.listFiles.nn
         .filter(_.nn.getName.nn.startsWith("scoverage"))
@@ -110,8 +107,8 @@ class InstrumentCoverage extends MacroTransform with IdentityDenotTransformer:
       * @return the statement's id
       */
     private def recordStatement(tree: Tree, pos: SourcePosition, branch: Boolean)(using ctx: Context): Int =
-      val id = statementId
-      statementId += 1
+      val id = ctx.base.coverageStatementId
+      ctx.base.coverageStatementId += 1
 
       val sourceFile = pos.source
       val statement = Statement(