(138059051) URL: Appending to an empty file path results in an absolute path

Author: jrflat

Sources/FoundationEssentials/URL/URL.swift

@@ -2214,9 +2214,8 @@ extension URL {
         var path = String(path)
         #endif
 
-        var newPath = relativePath()
         var insertedSlash = false
-        if !newPath.isEmpty && path.utf8.first != ._slash {
+        if !relativePath().isEmpty && path.utf8.first != ._slash {
             // Don't treat as first path segment when encoding
             path = "/" + path
             insertedSlash = true
@@ -2231,13 +2230,30 @@ extension URL {
             pathToAppend = String(decoding: utf8, as: UTF8.self)
         }
 
-        if newPath.utf8.last != ._slash && pathToAppend.utf8.first != ._slash {
-            newPath += "/"
-        } else if newPath.utf8.last == ._slash && pathToAppend.utf8.first == ._slash {
-            _ = newPath.popLast()
+        func appendedPath() -> String {
+            var currentPath = relativePath()
+            if currentPath.isEmpty && !hasAuthority {
+                guard _parseInfo.scheme == nil else {
+                    // Scheme only, append directly to the empty path, e.g.
+                    // URL("scheme:").appending(path: "path") == scheme:path
+                    return pathToAppend
+                }
+                // No scheme or authority, treat the empty path as "."
+                currentPath = "."
+            }
+
+            // If currentPath is empty, pathToAppend is relative, and we have an authority,
+            // we must append a slash to separate the path from authority, which happens below.
+
+            if currentPath.utf8.last != ._slash && pathToAppend.utf8.first != ._slash {
+                currentPath += "/"
+            } else if currentPath.utf8.last == ._slash && pathToAppend.utf8.first == ._slash {
+                _ = currentPath.popLast()
+            }
+            return currentPath + pathToAppend
         }
 
-        newPath += pathToAppend
+        var newPath = appendedPath()
 
         let hasTrailingSlash = newPath.utf8.last == ._slash
         let isDirectory: Bool

Tests/FoundationEssentialsTests/URLTests.swift

@@ -23,6 +23,18 @@ import TestSupport
 @testable import Foundation
 #endif
 
+private func checkBehavior<T: Equatable>(_ result: T, new: T, old: T, file: StaticString = #filePath, line: UInt = #line) {
+    #if FOUNDATION_FRAMEWORK
+    if foundation_swift_url_enabled() {
+        XCTAssertEqual(result, new, file: file, line: line)
+    } else {
+        XCTAssertEqual(result, old, file: file, line: line)
+    }
+    #else
+    XCTAssertEqual(result, new, file: file, line: line)
+    #endif
+}
+
 final class URLTests : XCTestCase {
 
     func testURLBasics() throws {
@@ -87,11 +99,7 @@ final class URLTests : XCTestCase {
         XCTAssertEqual(relativeURLWithBase.password(), baseURL.password())
         XCTAssertEqual(relativeURLWithBase.host(), baseURL.host())
         XCTAssertEqual(relativeURLWithBase.port, baseURL.port)
-        #if !FOUNDATION_FRAMEWORK_NSURL
-        XCTAssertEqual(relativeURLWithBase.path(), "/base/relative/path")
-        #else
-        XCTAssertEqual(relativeURLWithBase.path(), "relative/path")
-        #endif
+        checkBehavior(relativeURLWithBase.path(), new: "/base/relative/path", old: "relative/path")
         XCTAssertEqual(relativeURLWithBase.relativePath, "relative/path")
         XCTAssertEqual(relativeURLWithBase.query(), "query")
         XCTAssertEqual(relativeURLWithBase.fragment(), "fragment")
@@ -154,7 +162,7 @@ final class URLTests : XCTestCase {
             "http:g"        :  "http:g", // For strict parsers
         ]
 
-        #if FOUNDATION_FRAMEWORK_NSURL
+        #if FOUNDATION_FRAMEWORK
         let testsFailingWithoutSwiftURL = Set([
             "",
             "../../../g",
@@ -165,8 +173,8 @@ final class URLTests : XCTestCase {
         #endif
 
         for test in tests {
-            #if FOUNDATION_FRAMEWORK_NSURL
-            if testsFailingWithoutSwiftURL.contains(test.key) {
+            #if FOUNDATION_FRAMEWORK
+            if !foundation_swift_url_enabled(), testsFailingWithoutSwiftURL.contains(test.key) {
                 continue
             }
             #endif
@@ -178,8 +186,8 @@ final class URLTests : XCTestCase {
     }
 
     func testURLPathAPIsResolveAgainstBase() throws {
-        #if FOUNDATION_FRAMEWORK_NSURL
-        try XCTSkipIf(true)
+        #if FOUNDATION_FRAMEWORK
+        try XCTSkipIf(!foundation_swift_url_enabled())
         #endif
         // Borrowing the same test cases from RFC 3986, but checking paths
         let base = URL(string: "http://a/b/c/d;p?q")
@@ -246,8 +254,8 @@ final class URLTests : XCTestCase {
     }
 
     func testURLPathComponentsPercentEncodedSlash() throws {
-        #if FOUNDATION_FRAMEWORK_NSURL
-        try XCTSkipIf(true)
+        #if FOUNDATION_FRAMEWORK
+        try XCTSkipIf(!foundation_swift_url_enabled())
         #endif
 
         var url = try XCTUnwrap(URL(string: "https://example.com/https%3A%2F%2Fexample.com"))
@@ -270,8 +278,8 @@ final class URLTests : XCTestCase {
     }
 
     func testURLRootlessPath() throws {
-        #if FOUNDATION_FRAMEWORK_NSURL
-        try XCTSkipIf(true)
+        #if FOUNDATION_FRAMEWORK
+        try XCTSkipIf(!foundation_swift_url_enabled())
         #endif
 
         let paths = ["", "path"]
@@ -565,13 +573,8 @@ final class URLTests : XCTestCase {
         // `appending(component:)` should explicitly treat `component` as a single
         // path component, meaning "/" should be encoded to "%2F" before appending
         appended = url.appending(component: slashComponent, directoryHint: .notDirectory)
-        #if FOUNDATION_FRAMEWORK_NSURL
-        XCTAssertEqual(appended.absoluteString, "file:///var/mobile/relative/with:slash")
-        XCTAssertEqual(appended.relativePath, "relative/with:slash")
-        #else
-        XCTAssertEqual(appended.absoluteString, "file:///var/mobile/relative/%2Fwith:slash")
-        XCTAssertEqual(appended.relativePath, "relative/%2Fwith:slash")
-        #endif
+        checkBehavior(appended.absoluteString, new: "file:///var/mobile/relative/%2Fwith:slash", old: "file:///var/mobile/relative/with:slash")
+        checkBehavior(appended.relativePath, new: "relative/%2Fwith:slash", old: "relative/with:slash")
 
         appended = url.appendingPathComponent(component, isDirectory: false)
         XCTAssertEqual(appended.absoluteString, "file:///var/mobile/relative/no:slash")
@@ -685,12 +688,48 @@ final class URLTests : XCTestCase {
         XCTAssertEqual(url.path(), "/path.foo/")
         url.append(path: "/////")
         url.deletePathExtension()
-        #if !FOUNDATION_FRAMEWORK_NSURL
-        XCTAssertEqual(url.path(), "/path/")
-        #else
         // Old behavior only searches the last empty component, so the extension isn't actually removed
-        XCTAssertEqual(url.path(), "/path.foo///")
-        #endif
+        checkBehavior(url.path(), new: "/path/", old: "/path.foo///")
+    }
+
+    func testURLAppendingToEmptyPath() throws {
+        let baseURL = URL(filePath: "/base/directory", directoryHint: .isDirectory)
+        let emptyPathURL = URL(filePath: "", relativeTo: baseURL)
+        let url = emptyPathURL.appending(path: "main.swift")
+        XCTAssertEqual(url.relativePath, "./main.swift")
+        XCTAssertEqual(url.path, "/base/directory/main.swift")
+
+        var example = try XCTUnwrap(URL(string: "https://example.com"))
+        XCTAssertEqual(example.host(), "example.com")
+        XCTAssertTrue(example.path().isEmpty)
+
+        // Appending to an empty path should add a slash if an authority exists
+        // The appended path should never become part of the host
+        example.append(path: "foo")
+        XCTAssertEqual(example.host(), "example.com")
+        XCTAssertEqual(example.path(), "/foo")
+        XCTAssertEqual(example.absoluteString, "https://example.com/foo")
+
+        var emptyHost = try XCTUnwrap(URL(string: "scheme://"))
+        XCTAssertTrue(emptyHost.host()?.isEmpty ?? true)
+        XCTAssertTrue(emptyHost.path().isEmpty)
+
+        emptyHost.append(path: "foo")
+        XCTAssertTrue(emptyHost.host()?.isEmpty ?? true)
+        // Old behavior failed to append correctly to an empty host
+        // Modern parsers agree that "foo" relative to "scheme://" is "scheme:///foo"
+        checkBehavior(emptyHost.path(), new: "/foo", old: "")
+        checkBehavior(emptyHost.absoluteString, new: "scheme:///foo", old: "scheme://")
+
+        var schemeOnly = try XCTUnwrap(URL(string: "scheme:"))
+        XCTAssertTrue(schemeOnly.host()?.isEmpty ?? true)
+        XCTAssertTrue(schemeOnly.path().isEmpty)
+
+        schemeOnly.append(path: "foo")
+        XCTAssertTrue(schemeOnly.host()?.isEmpty ?? true)
+        // Old behavior appends to the string, but is missing the path
+        checkBehavior(schemeOnly.path(), new: "foo", old: "")
+        XCTAssertEqual(schemeOnly.absoluteString, "scheme:foo")
     }
 
     func testURLComponentsPercentEncodedUnencodedProperties() throws {