util: Add ArgsManager::GetPathArg() function

Co-authored-by: Ryan Ofsky <ryan@ofsky.org>

src/test/getarg_tests.cpp

@@ -159,6 +159,98 @@ BOOST_AUTO_TEST_CASE(intarg)
     BOOST_CHECK_EQUAL(m_local_args.GetIntArg("-bar", 11), 0);
 }
 
+BOOST_AUTO_TEST_CASE(patharg)
+{
+    const auto dir = std::make_pair("-dir", ArgsManager::ALLOW_ANY);
+    SetupArgs({dir});
+    ResetArgs("");
+    BOOST_CHECK_EQUAL(m_local_args.GetPathArg("-dir"), fs::path{});
+
+    const fs::path root_path{"/"};
+    ResetArgs("-dir=/");
+    BOOST_CHECK_EQUAL(m_local_args.GetPathArg("-dir"), root_path);
+
+    ResetArgs("-dir=/.");
+    BOOST_CHECK_EQUAL(m_local_args.GetPathArg("-dir"), root_path);
+
+    ResetArgs("-dir=/./");
+    BOOST_CHECK_EQUAL(m_local_args.GetPathArg("-dir"), root_path);
+
+    ResetArgs("-dir=/.//");
+    BOOST_CHECK_EQUAL(m_local_args.GetPathArg("-dir"), root_path);
+
+#ifdef WIN32
+    const fs::path win_root_path{"C:\\"};
+    ResetArgs("-dir=C:\\");
+    BOOST_CHECK_EQUAL(m_local_args.GetPathArg("-dir"), win_root_path);
+
+    ResetArgs("-dir=C:/");
+    BOOST_CHECK_EQUAL(m_local_args.GetPathArg("-dir"), win_root_path);
+
+    ResetArgs("-dir=C:\\\\");
+    BOOST_CHECK_EQUAL(m_local_args.GetPathArg("-dir"), win_root_path);
+
+    ResetArgs("-dir=C:\\.");
+    BOOST_CHECK_EQUAL(m_local_args.GetPathArg("-dir"), win_root_path);
+
+    ResetArgs("-dir=C:\\.\\");
+    BOOST_CHECK_EQUAL(m_local_args.GetPathArg("-dir"), win_root_path);
+
+    ResetArgs("-dir=C:\\.\\\\");
+    BOOST_CHECK_EQUAL(m_local_args.GetPathArg("-dir"), win_root_path);
+#endif
+
+    const fs::path absolute_path{"/home/user/.bitcoin"};
+    ResetArgs("-dir=/home/user/.bitcoin");
+    BOOST_CHECK_EQUAL(m_local_args.GetPathArg("-dir"), absolute_path);
+
+    ResetArgs("-dir=/root/../home/user/.bitcoin");
+    BOOST_CHECK_EQUAL(m_local_args.GetPathArg("-dir"), absolute_path);
+
+    ResetArgs("-dir=/home/./user/.bitcoin");
+    BOOST_CHECK_EQUAL(m_local_args.GetPathArg("-dir"), absolute_path);
+
+    ResetArgs("-dir=/home/user/.bitcoin/");
+    BOOST_CHECK_EQUAL(m_local_args.GetPathArg("-dir"), absolute_path);
+
+    ResetArgs("-dir=/home/user/.bitcoin//");
+    BOOST_CHECK_EQUAL(m_local_args.GetPathArg("-dir"), absolute_path);
+
+    ResetArgs("-dir=/home/user/.bitcoin/.");
+    BOOST_CHECK_EQUAL(m_local_args.GetPathArg("-dir"), absolute_path);
+
+    ResetArgs("-dir=/home/user/.bitcoin/./");
+    BOOST_CHECK_EQUAL(m_local_args.GetPathArg("-dir"), absolute_path);
+
+    ResetArgs("-dir=/home/user/.bitcoin/.//");
+    BOOST_CHECK_EQUAL(m_local_args.GetPathArg("-dir"), absolute_path);
+
+    const fs::path relative_path{"user/.bitcoin"};
+    ResetArgs("-dir=user/.bitcoin");
+    BOOST_CHECK_EQUAL(m_local_args.GetPathArg("-dir"), relative_path);
+
+    ResetArgs("-dir=somewhere/../user/.bitcoin");
+    BOOST_CHECK_EQUAL(m_local_args.GetPathArg("-dir"), relative_path);
+
+    ResetArgs("-dir=user/./.bitcoin");
+    BOOST_CHECK_EQUAL(m_local_args.GetPathArg("-dir"), relative_path);
+
+    ResetArgs("-dir=user/.bitcoin/");
+    BOOST_CHECK_EQUAL(m_local_args.GetPathArg("-dir"), relative_path);
+
+    ResetArgs("-dir=user/.bitcoin//");
+    BOOST_CHECK_EQUAL(m_local_args.GetPathArg("-dir"), relative_path);
+
+    ResetArgs("-dir=user/.bitcoin/.");
+    BOOST_CHECK_EQUAL(m_local_args.GetPathArg("-dir"), relative_path);
+
+    ResetArgs("-dir=user/.bitcoin/./");
+    BOOST_CHECK_EQUAL(m_local_args.GetPathArg("-dir"), relative_path);
+
+    ResetArgs("-dir=user/.bitcoin/.//");
+    BOOST_CHECK_EQUAL(m_local_args.GetPathArg("-dir"), relative_path);
+}
+
 BOOST_AUTO_TEST_CASE(doubledash)
 {
     const auto foo = std::make_pair("-foo", ArgsManager::ALLOW_ANY);

src/util/system.cpp

@@ -399,6 +399,13 @@ std::optional<unsigned int> ArgsManager::GetArgFlags(const std::string& name) co
     return std::nullopt;
 }
 
+fs::path ArgsManager::GetPathArg(std::string pathlike_arg) const
+{
+    auto result = fs::PathFromString(GetArg(pathlike_arg, "")).lexically_normal();
+    // Remove trailing slash, if present.
+    return result.has_filename() ? result : result.parent_path();
+}
+
 const fs::path& ArgsManager::GetBlocksDirPath() const
 {
     LOCK(cs_args);

src/util/system.h

@@ -264,6 +264,16 @@ protected:
      */
     std::optional<const Command> GetCommand() const;
 
+    /**
+     * Get a normalized path from a specified pathlike argument
+     *
+     * It is guaranteed that the returned path has no trailing slashes.
+     *
+     * @param pathlike_arg Pathlike argument to get a path from (e.g., "-datadir", "-blocksdir" or "-walletdir")
+     * @return Normalized path which is get from a specified pathlike argument
+     */
+    fs::path GetPathArg(std::string pathlike_arg) const;
+
     /**
      * Get blocks directory path
      *