Merge bitcoin/bitcoin#24306: util: Make ArgsManager::GetPathArg more widely usable

60aa179d8f9a675efa2d78eaadc09e3ba450f50f Use GetPathArg where possible (Pavol Rusnak)
5b946edd73640c6ecdfb4cbac1d4351e634678dc util, refactor: Use GetPathArg to read "-settings" value (Ryan Ofsky)
687e655ae2970f2f13aca0267c7de86dc69be763 util: Add GetPathArg default path argument (Ryan Ofsky)

Pull request description:

  Improve `ArgsManager::GetPathArg` method added in recent PR #24265, so it is usable more places. This PR starts to use it for the `-settings` option. This can also be helpful for #24274 which is parsing more path options.

  - Add `GetPathArg` default argument so it is less awkward to use to parse options that have default values.
  - Fix `GetPathArg` negated argument handling. Return path{} not path{"0"} when path argument is negated.
  - Add unit tests for default and negated cases
  - Move `GetPathArg` method declaration next to `GetArg` declaration. The two methods are close substitutes for each, so this should help keep them consistent and make them more discoverable.

ACKs for top commit:
  w0xlt:
    Tested ACK 60aa179 on Ubuntu 21.10
  hebasto:
    re-ACK 60aa179d8f9a675efa2d78eaadc09e3ba450f50f

Tree-SHA512: 3d24b885d8bbeef39ea5d0556e2f09b9e5f4a21179cef11cbbbc1b84da29c8fb66ba698889054ce28d80bc25926687654c8532ed46054bf5b2dd1837866bd1cd

6 files changed, 43 insertions, 23 deletions

diff --git a/src/bench/bench_bitcoin.cpp b/src/bench/bench_bitcoin.cpp
index 3f8bff4bcf..d6f9c0f8b5 100644
--- a/src/bench/bench_bitcoin.cpp
+++ b/src/bench/bench_bitcoin.cpp
@@ -109,8 +109,8 @@ int main(int argc, char** argv)
     args.asymptote = parseAsymptote(argsman.GetArg("-asymptote", ""));
     args.is_list_only = argsman.GetBoolArg("-list", false);
     args.min_time = std::chrono::milliseconds(argsman.GetIntArg("-min_time", DEFAULT_MIN_TIME_MS));
-    args.output_csv = fs::PathFromString(argsman.GetArg("-output_csv", ""));
-    args.output_json = fs::PathFromString(argsman.GetArg("-output_json", ""));
+    args.output_csv = argsman.GetPathArg("-output_csv");
+    args.output_json = argsman.GetPathArg("-output_json");
     args.regex_filter = argsman.GetArg("-filter", DEFAULT_BENCH_FILTER);
 
     benchmark::BenchRunner::RunAll(args);
diff --git a/src/init.cpp b/src/init.cpp
index a3d53c3fae..3110797194 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -135,7 +135,7 @@ static const char* BITCOIN_PID_FILENAME = "bitcoind.pid";
 
 static fs::path GetPidFile(const ArgsManager& args)
 {
-    return AbsPathForConfigVal(fs::PathFromString(args.GetArg("-pid", BITCOIN_PID_FILENAME)));
+    return AbsPathForConfigVal(args.GetPathArg("-pid", BITCOIN_PID_FILENAME));
 }
 
 [[nodiscard]] static bool CreatePidFile(const ArgsManager& args)
@@ -1229,10 +1229,7 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
         // Read asmap file if configured
         std::vector<bool> asmap;
         if (args.IsArgSet("-asmap")) {
-            fs::path asmap_path = fs::PathFromString(args.GetArg("-asmap", ""));
-            if (asmap_path.empty()) {
-                asmap_path = fs::PathFromString(DEFAULT_ASMAP_FILENAME);
-            }
+            fs::path asmap_path = args.GetPathArg("-asmap", DEFAULT_ASMAP_FILENAME);
             if (!asmap_path.is_absolute()) {
                 asmap_path = gArgs.GetDataDirNet() / asmap_path;
             }
diff --git a/src/init/common.cpp b/src/init/common.cpp
index 38c60366e3..688471b35d 100644
--- a/src/init/common.cpp
+++ b/src/init/common.cpp
@@ -81,7 +81,7 @@ void AddLoggingArgs(ArgsManager& argsman)
 void SetLoggingOptions(const ArgsManager& args)
 {
     LogInstance().m_print_to_file = !args.IsArgNegated("-debuglogfile");
-    LogInstance().m_file_path = AbsPathForConfigVal(fs::PathFromString(args.GetArg("-debuglogfile", DEFAULT_DEBUGLOGFILE)));
+    LogInstance().m_file_path = AbsPathForConfigVal(args.GetPathArg("-debuglogfile", DEFAULT_DEBUGLOGFILE));
     LogInstance().m_print_to_console = args.GetBoolArg("-printtoconsole", !args.GetBoolArg("-daemon", false));
     LogInstance().m_log_timestamps = args.GetBoolArg("-logtimestamps", DEFAULT_LOGTIMESTAMPS);
     LogInstance().m_log_time_micros = args.GetBoolArg("-logtimemicros", DEFAULT_LOGTIMEMICROS);
diff --git a/src/test/getarg_tests.cpp b/src/test/getarg_tests.cpp
index ef9d72dcde..76a65ec528 100644
--- a/src/test/getarg_tests.cpp
+++ b/src/test/getarg_tests.cpp
@@ -245,6 +245,24 @@ BOOST_AUTO_TEST_CASE(patharg)
 
     ResetArgs(local_args, "-dir=user/.bitcoin/.//");
     BOOST_CHECK_EQUAL(local_args.GetPathArg("-dir"), relative_path);
+
+    // Check negated and default argument handling. Specifying an empty argument
+    // is the same as not specifying the argument. This is convenient for
+    // scripting so later command line arguments can override earlier command
+    // line arguments or bitcoin.conf values. Currently the -dir= case cannot be
+    // distinguished from -dir case with no assignment, but #16545 would add the
+    // ability to distinguish these in the future (and treat the no-assign case
+    // like an imperative command or an error).
+    ResetArgs(local_args, "");
+    BOOST_CHECK_EQUAL(local_args.GetPathArg("-dir", "default"), fs::path{"default"});
+    ResetArgs(local_args, "-dir=override");
+    BOOST_CHECK_EQUAL(local_args.GetPathArg("-dir", "default"), fs::path{"override"});
+    ResetArgs(local_args, "-dir=");
+    BOOST_CHECK_EQUAL(local_args.GetPathArg("-dir", "default"), fs::path{"default"});
+    ResetArgs(local_args, "-dir");
+    BOOST_CHECK_EQUAL(local_args.GetPathArg("-dir", "default"), fs::path{"default"});
+    ResetArgs(local_args, "-nodir");
+    BOOST_CHECK_EQUAL(local_args.GetPathArg("-dir", "default"), fs::path{""});
 }
 
 BOOST_AUTO_TEST_CASE(doubledash)
diff --git a/src/util/system.cpp b/src/util/system.cpp
index aa9122106b..1ad701c56d 100644
--- a/src/util/system.cpp
+++ b/src/util/system.cpp
@@ -387,9 +387,12 @@ std::optional<unsigned int> ArgsManager::GetArgFlags(const std::string& name) co
     return std::nullopt;
 }
 
-fs::path ArgsManager::GetPathArg(std::string pathlike_arg) const
+fs::path ArgsManager::GetPathArg(std::string arg, const fs::path& default_value) const
 {
-    auto result = fs::PathFromString(GetArg(pathlike_arg, "")).lexically_normal();
+    if (IsArgNegated(arg)) return fs::path{};
+    std::string path_str = GetArg(arg, "");
+    if (path_str.empty()) return default_value;
+    fs::path result = fs::PathFromString(path_str).lexically_normal();
     // Remove trailing slash, if present.
     return result.has_filename() ? result : result.parent_path();
 }
@@ -516,12 +519,12 @@ bool ArgsManager::InitSettings(std::string& error)
 
 bool ArgsManager::GetSettingsPath(fs::path* filepath, bool temp) const
 {
-    if (IsArgNegated("-settings")) {
+    fs::path settings = GetPathArg("-settings", fs::path{BITCOIN_SETTINGS_FILENAME});
+    if (settings.empty()) {
         return false;
     }
     if (filepath) {
-        std::string settings = GetArg("-settings", BITCOIN_SETTINGS_FILENAME);
-        *filepath = fsbridge::AbsPathJoin(GetDataDirNet(), fs::PathFromString(temp ? settings + ".tmp" : settings));
+        *filepath = fsbridge::AbsPathJoin(GetDataDirNet(), temp ? settings + ".tmp" : settings);
     }
     return true;
 }
diff --git a/src/util/system.h b/src/util/system.h
index f193c8ac0b..a66b597d41 100644
--- a/src/util/system.h
+++ b/src/util/system.h
@@ -271,16 +271,6 @@ 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
      *
      * @return Blocks path which is network specific
@@ -343,6 +333,18 @@ protected:
     std::string GetArg(const std::string& strArg, const std::string& strDefault) const;
 
     /**
+     * Return path argument or default value
+     *
+     * @param arg Argument to get a path from (e.g., "-datadir", "-blocksdir" or "-walletdir")
+     * @param default_value Optional default value to return instead of the empty path.
+     * @return normalized path if argument is set, with redundant "." and ".."
+     * path components and trailing separators removed (see patharg unit test
+     * for examples or implementation for details). If argument is empty or not
+     * set, default_value is returned unchanged.
+     */
+    fs::path GetPathArg(std::string arg, const fs::path& default_value = {}) const;
+
+    /**
      * Return integer argument or default value
      *
      * @param strArg Argument to get (e.g. "-foo")