ScalafmtSession: add formatOrError()

scalafmt-dynamic/src/main/scala/org/scalafmt/dynamic/ScalafmtDynamicSession.scala

@@ -18,6 +18,9 @@ final case class ScalafmtDynamicSession(
   override def format(file: Path, code: String): String =
     tryFormat(file, code).getOrElse(code)
 
+  override def formatOrError(file: Path, code: String): ScalafmtResult =
+    tryFormat(file, code).fold(new ScalafmtResult(_), new ScalafmtResult(_))
+
   override def matchesProjectFilters(file: Path): Boolean =
     cfg.isIncludedInProject(file)
 

scalafmt-interfaces/src/main/java/org/scalafmt/interfaces/ScalafmtResult.java

@@ -0,0 +1,16 @@
+package org.scalafmt.interfaces;
+
+public final class ScalafmtResult {
+    public final String value;
+    public final Throwable exception;
+
+    public ScalafmtResult(String value) {
+        this.value = value;
+        this.exception = null;
+    }
+
+    public ScalafmtResult(Throwable exception) {
+        this.exception = exception;
+        this.value = null;
+    }
+}

scalafmt-interfaces/src/main/java/org/scalafmt/interfaces/ScalafmtSession.java

@@ -19,6 +19,16 @@ public interface ScalafmtSession {
     String format(Path file, String code);
 
 
+    /**
+     * Format a single file with the given configuration.
+     *
+     * @param file relative or absolute path to the file being formatted. Used only for the path
+     *             name, the file does not have to exist on disk.
+     * @param code the text contents to format.
+     * @return the formatted contents if formatting was successful, otherwise an error.
+     */
+    ScalafmtResult formatOrError(Path file, String code);
+
     /**
      * Whether the path matches the 'project.{excludeFilters,includeFilters}' setting.
      * @param file path to match