create fallback virtualfile and warn

Author: bishabosha

sbt-bridge/src/dotty/tools/xsbt/CompilerBridgeDriver.java

@@ -21,6 +21,7 @@
 
 import java.io.IOException;
 import java.util.Comparator;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Arrays;
@@ -62,6 +63,25 @@ private static VirtualFile asVirtualFileOrNull(SourceFile sourceFile) {
     }
   }
 
+  private static void reportMissingFile(DelegatingReporter reporter, dotty.tools.dotc.interfaces.SourceFile sourceFile) {
+    String underline = String.join("", Collections.nCopies(sourceFile.path().length(), "^"));
+    String message =
+      sourceFile.path() + ": Missing virtual file\n" +
+      underline + "\n" +
+      "    Falling back to placeholder for the given source file (of class " + sourceFile.getClass().getName() + ")\n" +
+      "    This is likely a bug in incremental compilation for the Scala 3 compiler. Please report it to the Scala 3 maintainers.";
+    reporter.reportBasicWarning(message);
+  }
+
+  private static VirtualFile fallbackVirtualFile(DelegatingReporter reporter,
+      dotty.tools.dotc.interfaces.SourceFile sourceFile,
+      Map<String, VirtualFile> placeholders) {
+    return placeholders.computeIfAbsent(sourceFile.path(), path -> {
+      reportMissingFile(reporter, sourceFile);
+      return new PlaceholderVirtualFile(sourceFile);
+    });
+  }
+
   synchronized public void run(VirtualFile[] sources, AnalysisCallback callback, Logger log, Reporter delegate) {
     VirtualFile[] sortedSources = new VirtualFile[sources.length];
     System.arraycopy(sources, 0, sortedSources, 0, sources.length);
@@ -86,17 +106,19 @@ synchronized public void run(VirtualFile[] sources, AnalysisCallback callback, L
       }
     });
 
+    HashMap<String, VirtualFile> placeholders = new HashMap<>();
+
     IncrementalCallback incCallback = new IncrementalCallback(callback, sourceFile -> {
       if (sourceFile instanceof SourceFile) {
         SourceFile sf = (SourceFile) sourceFile;
         VirtualFile vf = asVirtualFileOrNull(sf);
         if (vf != null) {
           return vf;
         } else {
-          throw new IllegalStateException("Unknown source file: " + sourceFile.path());
+          return fallbackVirtualFile(reporter, sourceFile, placeholders);
         }
       } else {
-        throw new IllegalStateException("Unknown source file: " + sourceFile.path());
+        return fallbackVirtualFile(reporter, sourceFile, placeholders);
       }
     });
 

sbt-bridge/src/dotty/tools/xsbt/DelegatingReporter.java

@@ -19,6 +19,7 @@
 import xsbti.Position;
 import xsbti.Severity;
 
+import java.util.Collections;
 import java.util.function.*;
 
 final public class DelegatingReporter extends AbstractReporter {
@@ -60,6 +61,14 @@ public void doReport(Diagnostic dia, Context ctx) {
     delegate.log(new Problem(position, messageBuilder.toString(), severity, rendered.toString(), diagnosticCode, actions, lookup));
   }
 
+  public void reportBasicWarning(String message) {
+    Position position = PositionBridge.noPosition;
+    Severity severity = Severity.Warn;
+    String diagnosticCode = "-1"; // no error code
+    List<CodeAction> actions = Collections.emptyList();
+    delegate.log(new Problem(position, message, severity, message, diagnosticCode, actions, lookup));
+  }
+
   private static Severity severityOf(int level) {
     Severity severity;
     switch (level) {

sbt-bridge/src/dotty/tools/xsbt/PlaceholderVirtualFile.java

@@ -0,0 +1,29 @@
+package dotty.tools.xsbt;
+
+import dotty.tools.dotc.interfaces.SourceFile;
+import java.io.InputStream;
+import java.nio.charset.StandardCharsets;
+
+public final class PlaceholderVirtualFile extends xsbti.BasicVirtualFileRef implements xsbti.VirtualFile {
+
+  private final SourceFile sourceFile;
+
+  public PlaceholderVirtualFile(SourceFile sourceFile) {
+    super(sourceFile.path());
+    this.sourceFile = sourceFile;
+  }
+
+  private static byte[] toBytes(char[] chars) {
+    return new String(chars).getBytes(StandardCharsets.UTF_8);
+  }
+
+  public InputStream input() {
+    return new java.io.ByteArrayInputStream(toBytes(sourceFile.content()));
+  }
+
+  public long contentHash() {
+    int murmurHash3 = scala.util.hashing.MurmurHash3$.MODULE$.bytesHash(toBytes(sourceFile.content()));
+    return scala.util.hashing.package$.MODULE$.byteswap64((long) murmurHash3);
+  }
+
+}

sbt-test/tasty-compat/add-overload/build.sbt

@@ -16,7 +16,7 @@ lazy val `a-changes` = project.in(file("a-changes"))
 
 lazy val c = project.in(file("."))
   .settings(
-    scalacOptions ++= Seq("-from-tasty", "-Ycheck:readTasty"),
+    scalacOptions ++= Seq("-from-tasty", "-Ycheck:readTasty", "-Xfatal-warnings"),
     Compile / sources := Seq(new java.io.File("c-input/B.tasty")),
     Compile / unmanagedClasspath += (ThisBuild / baseDirectory).value / "c-input",
     Compile / classDirectory := (ThisBuild / baseDirectory).value / "c-output"