Better error messages when can't map because a class has more than 22…

… fields
softwaremill · Jan 11, 2024 · 9cd1800 · 9cd1800
1 parent e28308f
commit 9cd1800
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Showing 2 changed files with 17 additions and 6 deletions.
diff --git a/core/src/main/scala-2/sttp/tapir/internal/MapToMacro.scala b/core/src/main/scala-2/sttp/tapir/internal/MapToMacro.scala
@@ -85,14 +85,21 @@ private[tapir] object MapToMacro {
   ): Unit = {
     val tupleSymbol = tupleType.typeSymbol
     if (!tupleSymbol.fullName.startsWith("scala.Tuple") && caseClassUtil.fields.nonEmpty) {
-      c.abort(c.enclosingPosition, s"Expected source type to be a tuple, but got: $tupleType")
+      c.abort(c.enclosingPosition, s"Expected source type to be a tuple, but got: ${tupleType.dealias}")
     }
 
     if (caseClassUtil.fields.size != tupleTypeArgs.size) {
-      c.abort(
-        c.enclosingPosition,
-        s"The arity of the source type doesn't match the arity of the target type: $tupleType, ${caseClassUtil.t}"
-      )
+      if (caseClassUtil.fields.size > 22) {
+        c.abort(
+          c.enclosingPosition,
+          s"Cannot map to ${caseClassUtil.t}: arities of up to 22 are supported. If you need more inputs/outputs, map them to classes with less fields, and then combine these classes."
+        )
+      } else {
+        c.abort(
+          c.enclosingPosition,
+          s"The arity of the source type (${tupleTypeArgs.size}) doesn't match the arity of the target type (${caseClassUtil.fields.size}): ${tupleType.dealias}, ${caseClassUtil.t}"
+        )
+      }
     }
 
     caseClassUtil.fields.zip(tupleTypeArgs).foreach { case (caseClassField, tupleArg) =>

diff --git a/core/src/main/scala-3/sttp/tapir/internal/ComplietimeErrors.scala b/core/src/main/scala-3/sttp/tapir/internal/ComplietimeErrors.scala
@@ -10,7 +10,11 @@ private[tapir] object ComplietimeErrors {
   private def reportIncorrectMappingImpl[SOURCE: Type, TARGET: Type](using Quotes): Expr[Unit] = {
     import quotes.reflect.*
 
-    report.throwError(s"Failed to map ${Type.show[SOURCE]} into ${Type.show[TARGET]}")
+    if TypeRepr.of[TARGET].typeSymbol.declaredFields.size > 22 then
+      report.throwError(
+        s"Cannot map to ${Type.show[TARGET]}: arities of up to 22 are supported. If you need more inputs/outputs, map them to classes with less fields, and then combine these classes."
+      )
+    else report.throwError(s"Failed to map ${Type.show[SOURCE]} into ${Type.show[TARGET]}")
   }
 
 }