Configurable error depth

Summary:
Make subtyping error depth configurable via an environment variable, e.g., `EQWALIZER_ERROR_DEPTH=8 eqwalize module`.

By default, error depth is still set to 4.

Reviewed By: ilya-klyuchnikov

Differential Revision: D47717108

fbshipit-source-id: b7efa3140a35698fd591ec359003c6276a2aad1c

eqwalizer/src/main/resources/application.conf

@@ -15,4 +15,6 @@ eqwalizer {
     check_redundant_guards = ${?EQWALIZER_CHECK_REDUNDANT_GUARDS}
     mode = standalone
     mode = ${?EQWALIZER_MODE}
+    error_depth = 4
+    error_depth = ${?EQWALIZER_ERROR_DEPTH}
 }

eqwalizer/src/main/scala/com/whatsapp/eqwalizer/package.scala

@@ -50,6 +50,7 @@ package object eqwalizer {
       tolerateErrors: Boolean,
       checkRedundantGuards: Boolean,
       mode: Mode.Mode,
+      errorDepth: Int,
   ) {
     def useElp(): Boolean = {
       mode match {
@@ -79,6 +80,7 @@ package object eqwalizer {
       tolerateErrors = config.getBoolean("tolerate_errors"),
       checkRedundantGuards = config.getBoolean("check_redundant_guards"),
       mode,
+      errorDepth = config.getInt("error_depth"),
     )
   }
 }

eqwalizer/src/main/scala/com/whatsapp/eqwalizer/tc/SubtypeDetail.scala

@@ -10,7 +10,6 @@ import com.whatsapp.eqwalizer.ast.Types._
 import com.whatsapp.eqwalizer.ast.{RemoteId, Show, TypeVars}
 
 object SubtypeDetail {
-  private val maxDepth = 4
   lazy val nonVerboseRids = builtinTypes.keys.map(RemoteId("erlang", _, 0)).toSet
 
   private case class Detail(t1: Type, t2: Type, reasonPrefix: Option[String], reasonPostfix: Option[String])
@@ -83,7 +82,7 @@ class SubtypeDetail(pipelineContext: PipelineContext) {
     }
 
   private def findSubtypeMismatch(t1: Type, t2: Type): List[Detail] =
-    findMismatchAux(t1, t2, Nil, Set.empty).reverse.take(maxDepth)
+    findMismatchAux(t1, t2, Nil, Set.empty).reverse.take(pipelineContext.errorDepth)
 
   // keep this function in sync with subtype.subtype
   // Main differences from subtype.subtype's cases:

eqwalizer/src/main/scala/com/whatsapp/eqwalizer/tc/package.scala

@@ -22,6 +22,7 @@ package object tc {
       tolerateErrors: Option[Boolean] = None,
       unlimitedRefinement: Option[Boolean] = None,
       checkRedundantGuards: Option[Boolean] = None,
+      errorDepth: Option[Int] = None,
   )
 
   val noOptions: Options = Options()
@@ -65,5 +66,7 @@ package object tc {
       options.checkRedundantGuards.getOrElse(config.checkRedundantGuards)
     val typeInfo: TypeInfo =
       new TypeInfo(this)
+    val errorDepth: Int =
+      options.errorDepth.getOrElse(config.errorDepth)
   }
 }