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

Author: jrflat

Sources/FoundationEssentials/URL/URL.swift

@@ -2226,7 +2226,15 @@ extension URL {
             pathToAppend = String(decoding: utf8, as: UTF8.self)
         }
 
-        if newPath.utf8.last != ._slash && pathToAppend.utf8.first != ._slash {
+        // If the current path is empty (relative), don't append a slash which
+        // would make the path absolute--unless we have an authority.
+
+        // If we have an authority, we must add a slash to separate the path from the authority,
+        // e.g. URL("http://example.com").appending(path: "path") == "http://example.com/path"
+
+        if newPath.isEmpty && !hasAuthority {
+            // Do nothing, path will be directly appended
+        } else if newPath.utf8.last != ._slash && pathToAppend.utf8.first != ._slash {
             newPath += "/"
         } else if newPath.utf8.last == ._slash && pathToAppend.utf8.first == ._slash {
             _ = newPath.popLast()

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) {
+    #if FOUNDATION_FRAMEWORK
+    if foundation_swift_url_enabled() {
+        XCTAssertEqual(result, new)
+    } else {
+        XCTAssertEqual(result, old)
+    }
+    #else
+    XCTAssertEqual(result, new)
+    #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")
@@ -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 +688,49 @@ 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")
+        // New behavior keeps the path relative without needing to insert "."
+        checkBehavior(url.relativePath, new: "main.swift", old: "./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 {