Fixed indent inference

Sources/Inference.swift

@@ -47,15 +47,28 @@ public func inferFormatOptions(from tokens: [Token]) -> FormatOptions {
             }
             indents.append((indent, 0))
         }
+        var previousLength = 0
         formatter.forEach(.linebreak) { i, _ in
-            let start = formatter.startOfLine(at: i)
-            if case let .space(string) = formatter.tokens[start] {
+            if case let .space(string)? = formatter.token(at: i + 1) {
                 if string.hasPrefix("\t") {
                     increment("\t")
                 } else {
                     let length = string.count
-                    for i in [8, 4, 3, 2, 1] where length % i == 0 {
-                        increment(String(repeating: " ", count: i))
+                    let delta = previousLength - length
+                    if delta != 0 {
+                        switch formatter.token(at: i + 2) ?? .space("") {
+                        case .commentBody, .delimiter(","):
+                            return
+                        default:
+                            break
+                        }
+                        switch formatter.last(.nonSpaceOrCommentOrLinebreak, before: i) ?? .space("") {
+                        case .delimiter(","):
+                            break
+                        default:
+                            increment(String(repeating: " ", count: abs(delta)))
+                            previousLength = length
+                        }
                     }
                 }
             }

SwiftFormat.xcodeproj/project.pbxproj

@@ -18,7 +18,6 @@
 		01045AA0211A1EE300D2BE3D /* Arguments.swift in Sources */ = {isa = PBXBuildFile; fileRef = 01045A982119979400D2BE3D /* Arguments.swift */; };
 		010BC9A21DCFDF1E003F4F11 /* TokenizerTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 018E82741D62E730008CA0F8 /* TokenizerTests.swift */; };
 		012092821E2D9A3C008B0520 /* RulesTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 01A0EAB31D5DB4D000A0A8E3 /* RulesTests.swift */; };
-		012092851E2D9A7B008B0520 /* InferenceTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 01F3DF8F1DBA003E00454944 /* InferenceTests.swift */; };
 		012092861E2D9E14008B0520 /* FormatterTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 01B3987A1D763424009ADE61 /* FormatterTests.swift */; };
 		0142F06F1D72FE10007D66CC /* SwiftFormatTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 0142F06E1D72FE10007D66CC /* SwiftFormatTests.swift */; };
 		015AF2C01DC6A538008F0A8C /* SwiftFormat.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 01A0EAA41D5DB4CF00A0A8E3 /* SwiftFormat.framework */; };
@@ -687,7 +686,6 @@
 			files = (
 				012092861E2D9E14008B0520 /* FormatterTests.swift in Sources */,
 				012092821E2D9A3C008B0520 /* RulesTests.swift in Sources */,
-				012092851E2D9A7B008B0520 /* InferenceTests.swift in Sources */,
 				015AF2CA1DC6A58C008F0A8C /* PerformanceTests.swift in Sources */,
 				010BC9A21DCFDF1E003F4F11 /* TokenizerTests.swift in Sources */,
 			);

Tests/InferenceTests.swift

@@ -29,10 +29,33 @@
 //  SOFTWARE.
 //
 
-import SwiftFormat
+@testable import SwiftFormat
 import XCTest
 
 class InferenceTests: XCTestCase {
+    static let files: [String] = {
+        var files = [String]()
+        let inputURL = URL(fileURLWithPath: #file)
+            .deletingLastPathComponent().deletingLastPathComponent()
+
+        _ = enumerateFiles(withInputURL: inputURL) { url, _, _ in
+            return {
+                if let source = try? String(contentsOf: url) {
+                    files.append(source)
+                }
+            }
+        }
+        return files
+    }()
+
+    func testInferOptionsForProject() {
+        let files = InferenceTests.files
+        let tokens = files.flatMap { tokenize($0) }
+        let options = Options(formatOptions: inferFormatOptions(from: tokens))
+        let arguments = serialize(options: options, excludingDefaults: true, separator: " ")
+        XCTAssertEqual(arguments, "--binarygrouping none --decimalgrouping none --hexgrouping none --octalgrouping none --wraparguments afterfirst --wrapcollections beforefirst")
+    }
+
     // MARK: indent
 
     func testInferIndentLevel() {
@@ -40,14 +63,50 @@ class InferenceTests: XCTestCase {
         \t
         class Foo {
             func bar() {
-                //baz
-                //quux
-                //foo
+                baz()
+                quux()
+                let foo = Foo()
             }
         }
         """
         let options = inferFormatOptions(from: tokenize(input))
-        XCTAssertEqual(options.indent, "    ")
+        XCTAssertEqual(options.indent.count, 4)
+    }
+
+    func testInferIndentWithComment() {
+        let input = """
+        class Foo {
+            /*
+             A multiline comment
+              which has unusual
+               indenting that
+                might screw up
+                 the indent inference
+             */
+        }
+        """
+        let options = inferFormatOptions(from: tokenize(input))
+        XCTAssertEqual(options.indent.count, 4)
+    }
+
+    func testInferIndentWithWrappedFunction() {
+        let input = """
+        class Foo {
+            func foo(arg: Int,
+                     arg: Int,
+                     arg: Int) {}
+
+            func bar(arg: Int,
+                     arg: Int,
+                     arg: Int) {}
+
+            func baz(arg: Int,
+                     arg: Int,
+                     arg: Int) {}
+        }
+        """
+        let options = inferFormatOptions(from: tokenize(input))
+        XCTAssertEqual(options.indent.count, 4)
     }
 
     // MARK: linebreak

Tests/PerformanceTests.swift

@@ -102,9 +102,11 @@ class PerformanceTests: XCTestCase {
     func testInferring() {
         let files = PerformanceTests.files
         let tokens = files.flatMap { tokenize($0) }
+        var options: FormatOptions?
         measure {
-            _ = inferFormatOptions(from: tokens)
+            options = inferFormatOptions(from: tokens)
         }
+        XCTAssertEqual(options?.indent.count, 4)
     }
 
     func testIndent() {