Swift 4 + performance improvements (#8)

We ran into some serious performance improvements while using DoctorPretty for snapshot testing, so I wanted to see if there was anything I could do to fix it. I optimized a few small things (like using reduce(into:) with mutation instead of the pure version), but the real bottleneck is with the best and fits functions, which are recursive. I was able to rewrite fits as a plain loop, and that improved performance quite a bit, and we'd probably get huge improvements if we could rewrite best.

Author: mbrandonw

.swift-version

@@ -1 +1 @@
-3.1
+4.0

.travis.yml

@@ -1,14 +1,13 @@
 os:
   - linux
   - osx
-env: 
+env:
 language: generic
 sudo: required
 dist: trusty
-osx_image: xcode8.3
+osx_image: xcode9.2
 install:
   - eval "$(curl -sL https://gist.githubusercontent.com/kylef/5c0475ff02b7c7671d2a/raw/9f442512a46d7a2af7b850d65a7e9bd31edfb09b/swiftenv-install.sh)"
 script:
   - swift build
-  - SWIFTPM_TEST_DoctorPretty=YES swift test
-
+  - swift test

Package.resolved

@@ -1,21 +1,16 @@
-// swift-tools-version:3.1
+// swift-tools-version:4.0
 
 import PackageDescription
-import Foundation
-
-// HACK from https://github.com/ReactiveCocoa/ReactiveSwift/blob/master/Package.swift
-var isSwiftPMTest: Bool {
-    return ProcessInfo.processInfo.environment["SWIFTPM_TEST_DoctorPretty"] == "YES"
-}
 
 let package = Package(
     name: "DoctorPretty",
-    targets: [],
     dependencies: [
-        .Package(url: "https://github.com/typelift/Algebra.git", majorVersion: 0, minor: 2),
-        .Package(url: "https://github.com/typelift/Swiftx.git", majorVersion: 0, minor: 5)
-    ] + (isSwiftPMTest ?
-      [.Package(url: "https://github.com/typelift/SwiftCheck.git", versions: Version(0,6,0)..<Version(1,0,0))] :
-      [])
-
+        .package(url: "https://github.com/typelift/Algebra.git", .exact("0.2.0")),
+        .package(url: "https://github.com/typelift/Swiftx.git", .exact("0.6.0")),
+        .package(url: "https://github.com/typelift/SwiftCheck.git", .exact("0.9.1"))
+    ],
+    targets: [
+        .target(name: "DoctorPretty", dependencies: ["Algebra", "Swiftx"]),
+        .testTarget(name: "DoctorPrettyTests", dependencies: ["DoctorPretty", "SwiftCheck"]),
+        ]
 )

Package.swift

@@ -35,7 +35,7 @@ public indirect enum Doc {
     }
 
     public static func text(_ str: String) -> Doc {
-        return str == "" ? .empty : ._text(length: str.characters.count, str)
+        return str == "" ? .empty : ._text(length: str.count, str)
     }
 
     public static var line: Doc {

Sources/Alignment.swift Sources/DoctorPretty/Alignment.swiftSources/Alignment.swift renamed to Sources/DoctorPretty/Alignment.swift

@@ -14,9 +14,9 @@ extension BidirectionalCollection where Iterator.Element == Doc, IndexDistance =
     /// Intersperses punctuation inside docs
     public func punctuate(with punctuation: Doc) -> [Doc] {
         if let d = first {
-            return [d] + self.dropFirst().reduce([Doc]()) { t in
-                let (acc, d2) = t
-                return acc <> [punctuation, d2]
+            return [d] + self.dropFirst().reduce(into: [Doc]()) { acc, d2 in
+                acc.append(punctuation)
+                acc.append(d2)
             }
         } else {
             return []
@@ -47,8 +47,8 @@ extension BidirectionalCollection where Iterator.Element == Doc, IndexDistance =
         return (
             .nest(indent,
                   left <&&> punctuated.sep()
-            ) <&&> right
-        ).grouped
+                ) <&&> right
+            ).grouped
     }
 
     /// See @enclose
@@ -66,3 +66,4 @@ extension BidirectionalCollection where Iterator.Element == Doc, IndexDistance =
         return enclose(left: Doc.lbrace, right: Doc.rbrace, separator: Doc.semi, indent: indent)
     }
 }
+