From 4c018909f72719b8916cd1480216e9ecb7a16d7a Mon Sep 17 00:00:00 2001
From: Max Wipfli <mail@maxwipfli.ch>
Date: Tue, 29 Jun 2021 17:55:12 +0200
Subject: [PATCH] AK: Make LexicalPath immutable

This replaces the current LexicalPath::append() API with a new method
that returns a new LexicalPath object and doesn't touch the this-object.
With this, LexicalPath is now immutable. It also adds a
LexicalPath::parent() method and the relevant test cases.
---
 AK/LexicalPath.cpp           | 13 ++++++-------
 AK/LexicalPath.h             |  3 ++-
 Tests/AK/TestLexicalPath.cpp | 33 ++++++++++++++++++++++++++++++---
 3 files changed, 38 insertions(+), 11 deletions(-)

diff --git a/AK/LexicalPath.cpp b/AK/LexicalPath.cpp
index 8a9ae25155..2108ed940e 100644
--- a/AK/LexicalPath.cpp
+++ b/AK/LexicalPath.cpp
@@ -137,15 +137,14 @@ String LexicalPath::relative_path(String absolute_path, String const& prefix)
     return absolute_path.substring(prefix_length);
 }
 
-void LexicalPath::append(String const& component)
+LexicalPath LexicalPath::append(StringView const& value) const
 {
-    StringBuilder builder;
-    builder.append(m_string);
-    builder.append('/');
-    builder.append(component);
+    return LexicalPath::join(m_string, value);
+}
 
-    m_string = builder.to_string();
-    canonicalize();
+LexicalPath LexicalPath::parent() const
+{
+    return append("..");
 }
 
 }
diff --git a/AK/LexicalPath.h b/AK/LexicalPath.h
index 4c425c4ed3..8c4d71f409 100644
--- a/AK/LexicalPath.h
+++ b/AK/LexicalPath.h
@@ -30,7 +30,8 @@ public:
 
     bool has_extension(StringView const&) const;
 
-    void append(String const& component);
+    [[nodiscard]] LexicalPath append(StringView const&) const;
+    [[nodiscard]] LexicalPath parent() const;
 
     static String canonicalized_path(String);
     static String relative_path(String absolute_path, String const& prefix);
diff --git a/Tests/AK/TestLexicalPath.cpp b/Tests/AK/TestLexicalPath.cpp
index 7b6046580d..61832724fb 100644
--- a/Tests/AK/TestLexicalPath.cpp
+++ b/Tests/AK/TestLexicalPath.cpp
@@ -165,11 +165,38 @@ TEST_CASE(join)
     EXPECT_EQ(LexicalPath::join("anon", "foo.txt").string(), "anon/foo.txt");
     EXPECT_EQ(LexicalPath::join("/home", "anon/foo.txt").string(), "/home/anon/foo.txt");
     EXPECT_EQ(LexicalPath::join("/", "foo.txt").string(), "/foo.txt");
+    EXPECT_EQ(LexicalPath::join("/home", "anon", "foo.txt").string(), "/home/anon/foo.txt");
 }
 
 TEST_CASE(append)
 {
-    LexicalPath path("/home/anon");
-    path.append("foo.txt");
-    EXPECT_EQ(path.string(), "/home/anon/foo.txt");
+    LexicalPath path("/home/anon/");
+    auto new_path = path.append("foo.txt");
+    EXPECT_EQ(new_path.string(), "/home/anon/foo.txt");
+}
+
+TEST_CASE(parent)
+{
+    {
+        LexicalPath path("/home/anon/foo.txt");
+        auto parent = path.parent();
+        EXPECT_EQ(parent.string(), "/home/anon");
+    }
+    {
+        LexicalPath path("anon/foo.txt");
+        auto parent = path.parent();
+        EXPECT_EQ(parent.string(), "anon");
+    }
+    {
+        LexicalPath path("foo.txt");
+        auto parent = path.parent();
+        EXPECT_EQ(parent.string(), ".");
+        auto parent_of_parent = parent.parent();
+        EXPECT_EQ(parent_of_parent.string(), "..");
+    }
+    {
+        LexicalPath path("/");
+        auto parent = path.parent();
+        EXPECT_EQ(parent.string(), "/");
+    }
 }