Fix CustomDumpRepresentable max depth (#88)

* Fix `CustomDumpRepresentable` max depth

When we reach a custom dump representable value, we should not decrement
the max depth when printing it.

At times this can cause the max depth to roll from 0 to -1, which
currently causes the logic that collapses nodes to leave them expanded.

We should update that logic, as well, so I'll do that in another commit.

* Treat negative depth as zero

* Add/fix some unrelated tests

Author: stephencelis

Sources/CustomDump/Dump.swift

@@ -118,7 +118,7 @@ func _customDump<T, TargetStream>(
             maxDepth: maxDepth - 1
           )
           if childOut.contains("\n") {
-            if maxDepth == 0 {
+            if maxDepth <= 0 {
               out.write("…")
             } else {
               out.write("\n")
@@ -128,7 +128,7 @@ func _customDump<T, TargetStream>(
           } else {
             out.write(childOut)
           }
-        } else if maxDepth == 0 {
+        } else if maxDepth <= 0 {
           out.write("…")
         } else {
           out.write("\n")
@@ -165,7 +165,7 @@ func _customDump<T, TargetStream>(
 
     case let (value as CustomDumpRepresentable, _):
       customDumpHelp(
-        value.customDumpValue, to: &out, name: nil, indent: 0, isRoot: false, maxDepth: maxDepth - 1
+        value.customDumpValue, to: &out, name: nil, indent: 0, isRoot: false, maxDepth: maxDepth
       )
 
     case let (value as AnyObject, .class?):
@@ -287,7 +287,7 @@ func _customDump<T, TargetStream>(
     default:
       if let value = stringFromStringProtocol(value) {
         if value.contains(where: \.isNewline) {
-          if maxDepth == 0 {
+          if maxDepth <= 0 {
             out.write("\"…\"")
           } else {
             let hashes = String(repeating: "#", count: value.hashCount(isMultiline: true))

Tests/CustomDumpTests/DiffTests.swift

@@ -103,11 +103,11 @@ final class DiffTests: XCTestCase {
       diff(
         User(),
         User()
-      )?.replacingOccurrences(of: "0x[[:xdigit:]]+", with: "…", options: .regularExpression),
+      )?.replacingOccurrences(of: "0x[[:xdigit:]]+", with: "0x…", options: .regularExpression),
       """
         DiffTests.User(
-      -   _: ObjectIdentifier(…),
-      +   _: ObjectIdentifier(…),
+      -   _: ObjectIdentifier(0x…),
+      +   _: ObjectIdentifier(0x…),
           id: 42,
           name: "Blob"
         )
@@ -446,6 +446,29 @@ final class DiffTests: XCTestCase {
     )
   }
 
+  func testEnumCollapsing() {
+    enum Offset: Equatable {
+      case page(Int, perPage: Int = 10)
+    }
+    struct State: Equatable {
+      var offset: Offset
+      let result: String
+    }
+    XCTAssertNoDifference(
+      diff(
+        State(offset: .page(1), result: "Hello, world!"),
+        State(offset: .page(1), result: "Good night, moon!")
+      ),
+      """
+        DiffTests.State(
+          offset: .page(…),
+      -   result: "Hello, world!"
+      +   result: "Good night, moon!"
+        )
+      """
+    )
+  }
+
   func testOptional() {
     XCTAssertEqual(
       diff(nil as User?, nil), nil
@@ -1111,6 +1134,31 @@ final class DiffTests: XCTestCase {
       """
     )
   }
+
+  func testCustomDumpRepresentableCollapsing() {
+    struct Results: CustomDumpRepresentable, Equatable {
+      var customDumpValue: Any {
+        [1, 2]
+      }
+    }
+    struct State: Equatable {
+      var date: Double
+      var results: Results
+    }
+    XCTAssertNoDifference(
+      diff(
+        State(date: 123456789, results: Results()),
+        State(date: 123456790, results: Results())
+      ),
+      """
+        DiffTests.State(
+      -   date: 123456789.0,
+      +   date: 123456790.0,
+          results: […]
+        )
+      """
+    )
+  }
 }
 
 private struct Stack<State: Equatable>: CustomDumpReflectable, Equatable {