Merge pull request #13234 from xokdvium/transparent-comparator-map

Use C++14 N3657 transparent comparator for `StringMap` and `StringPairs` (NFC)

src/libcmd/include/nix/cmd/command.hh

@@ -336,7 +336,7 @@ struct MixEnvironment : virtual Args
 
     StringSet keepVars;
     StringSet unsetVars;
-    std::map<std::string, std::string> setVars;
+    StringMap setVars;
     bool ignoreEnvironment;
 
     MixEnvironment();

src/libfetchers/attrs.cc

@@ -89,9 +89,9 @@ bool getBoolAttr(const Attrs & attrs, const std::string & name)
     return *s;
 }
 
-std::map<std::string, std::string> attrsToQuery(const Attrs & attrs)
+StringMap attrsToQuery(const Attrs & attrs)
 {
-    std::map<std::string, std::string> query;
+    StringMap query;
     for (auto & attr : attrs) {
         if (auto v = std::get_if<uint64_t>(&attr.second)) {
             query.insert_or_assign(attr.first, fmt("%d", *v));

src/libfetchers/fetchers.cc

@@ -134,7 +134,7 @@ ParsedURL Input::toURL() const
     return scheme->toURL(*this);
 }
 
-std::string Input::toURLString(const std::map<std::string, std::string> & extraQuery) const
+std::string Input::toURLString(const StringMap & extraQuery) const
 {
     auto url = toURL();
     for (auto & attr : extraQuery)

src/libfetchers/git-utils.cc

@@ -368,7 +368,7 @@ struct GitRepoImpl : GitRepo, std::enable_shared_from_this<GitRepoImpl>
         if (git_config_iterator_glob_new(Setter(it), config.get(), "^submodule\\..*\\.(path|url|branch)$"))
             throw Error("iterating over .gitmodules: %s", git_error_last()->message);
 
-        std::map<std::string, std::string> entries;
+        StringMap entries;
 
         while (true) {
             git_config_entry * entry = nullptr;

src/libfetchers/include/nix/fetchers/attrs.hh

@@ -37,7 +37,7 @@ std::optional<bool> maybeGetBoolAttr(const Attrs & attrs, const std::string & na
 
 bool getBoolAttr(const Attrs & attrs, const std::string & name);
 
-std::map<std::string, std::string> attrsToQuery(const Attrs & attrs);
+StringMap attrsToQuery(const Attrs & attrs);
 
 Hash getRevAttr(const Attrs & attrs, const std::string & name);
 

src/libfetchers/include/nix/fetchers/fetchers.hh

@@ -71,7 +71,7 @@ public:
 
     ParsedURL toURL() const;
 
-    std::string toURLString(const std::map<std::string, std::string> & extraQuery = {}) const;
+    std::string toURLString(const StringMap & extraQuery = {}) const;
 
     std::string to_string() const;
 

src/libflake/flakeref.cc

@@ -15,7 +15,7 @@ const static std::string subDirRegex = subDirElemRegex + "(?:/" + subDirElemRege
 
 std::string FlakeRef::to_string() const
 {
-    std::map<std::string, std::string> extraQuery;
+    StringMap extraQuery;
     if (subdir != "")
         extraQuery.insert_or_assign("dir", subdir);
     return input.toURLString(extraQuery);

src/libstore/build/derivation-goal.cc

@@ -974,7 +974,7 @@ void runPostBuildHook(
             fmt("running post-build-hook '%s'", settings.postBuildHook),
             Logger::Fields{store.printStorePath(drvPath)});
     PushActivity pact(act.id);
-    std::map<std::string, std::string> hookEnvironment = getEnv();
+    StringMap hookEnvironment = getEnv();
 
     hookEnvironment.emplace("DRV_PATH", store.printStorePath(drvPath));
     hookEnvironment.emplace("OUT_PATHS", chomp(concatStringsSep(" ", store.printStorePathSet(outputPaths))));

src/libstore/include/nix/store/store-dir-config.hh

@@ -125,7 +125,7 @@ struct StoreDirConfigBase : Config
  */
 struct StoreDirConfig : StoreDirConfigBase, MixStoreDirMethods
 {
-    using Params = std::map<std::string, std::string>;
+    using Params = StringMap;
 
     StoreDirConfig(const Params & params);
 

src/libstore/include/nix/store/store-reference.hh

@@ -41,7 +41,7 @@ namespace nix {
  */
 struct StoreReference
 {
-    using Params = std::map<std::string, std::string>;
+    using Params = StringMap;
 
     /**
      * Special store reference `""` or `"auto"`

src/libstore/realisation.cc

@@ -96,7 +96,7 @@ Realisation Realisation::fromJSON(
 
     std::map <DrvOutput, StorePath> dependentRealisations;
     if (auto jsonDependencies = json.find("dependentRealisations"); jsonDependencies != json.end())
-        for (auto & [jsonDepId, jsonDepOutPath] : jsonDependencies->get<std::map<std::string, std::string>>())
+        for (auto & [jsonDepId, jsonDepOutPath] : jsonDependencies->get<StringMap>())
             dependentRealisations.insert({DrvOutput::parse(jsonDepId), StorePath(jsonDepOutPath)});
 
     return Realisation{

src/libstore/ssh.cc

@@ -83,7 +83,7 @@ bool SSHMaster::isMasterRunning() {
 Strings createSSHEnv()
 {
     // Copy the environment and set SHELL=/bin/sh
-    std::map<std::string, std::string> env = getEnv();
+    StringMap env = getEnv();
 
     // SSH will invoke the "user" shell for -oLocalCommand, but that means
     // $SHELL. To keep things simple and avoid potential issues with other

src/libstore/unix/build/derivation-builder.cc

@@ -187,7 +187,7 @@ private:
     typedef std::map<Path, ChrootPath> PathsInChroot; // maps target path to source path
     PathsInChroot pathsInChroot;
 
-    typedef std::map<std::string, std::string> Environment;
+    typedef StringMap Environment;
     Environment env;
 
     /**

src/libutil-tests/strings.cc

@@ -106,7 +106,7 @@ TEST(concatMapStringsSep, two)
 
 TEST(concatMapStringsSep, map)
 {
-    std::map<std::string, std::string> strings;
+    StringMap strings;
     strings["this"] = "that";
     strings["1"] = "one";
 

src/libutil-tests/url.cc

@@ -5,8 +5,8 @@ namespace nix {
 
 /* ----------- tests for url.hh --------------------------------------------------*/
 
-    std::string print_map(std::map<std::string, std::string> m) {
+    std::string print_map(StringMap m) {
-        std::map<std::string, std::string>::iterator it;
+        StringMap::iterator it;
         std::string s = "{ ";
         for (it = m.begin(); it != m.end(); ++it) {
             s += "{ ";

src/libutil/archive.cc

@@ -72,7 +72,7 @@ void SourceAccessor::dumpPath(
 
             /* If we're on a case-insensitive system like macOS, undo
                the case hack applied by restorePath(). */
-            std::map<std::string, std::string> unhacked;
+            StringMap unhacked;
             for (auto & i : readDirectory(path))
                 if (archiveSettings.useCaseHack) {
                     std::string name(i.first);

src/libutil/environment-variables.cc

@@ -21,9 +21,9 @@ std::optional<std::string> getEnvNonEmpty(const std::string & key)
     return value;
 }
 
-std::map<std::string, std::string> getEnv()
+StringMap getEnv()
 {
-    std::map<std::string, std::string> env;
+    StringMap env;
     for (size_t i = 0; environ[i]; ++i) {
         auto s = environ[i];
         auto eq = strchr(s, '=');
@@ -41,7 +41,7 @@ void clearEnv()
         unsetenv(name.first.c_str());
 }
 
-void replaceEnv(const std::map<std::string, std::string> & newEnv)
+void replaceEnv(const StringMap & newEnv)
 {
     clearEnv();
     for (auto & newEnvVar : newEnv)

src/libutil/include/nix/util/environment-variables.hh

@@ -34,7 +34,7 @@ std::optional<std::string> getEnvNonEmpty(const std::string & key);
 /**
  * Get the entire environment.
  */
-std::map<std::string, std::string> getEnv();
+StringMap getEnv();
 
 #ifdef _WIN32
 /**
@@ -64,6 +64,6 @@ void clearEnv();
 /**
  * Replace the entire environment with the given one.
  */
-void replaceEnv(const std::map<std::string, std::string> & newEnv);
+void replaceEnv(const StringMap & newEnv);
 
 }

src/libutil/include/nix/util/processes.hh

@@ -103,7 +103,7 @@ struct RunOptions
     std::optional<uid_t> gid;
 #endif
     std::optional<Path> chdir;
-    std::optional<std::map<std::string, std::string>> environment;
+    std::optional<StringMap> environment;
     std::optional<std::string> input;
     Source * standardIn = nullptr;
     Sink * standardOut = nullptr;

src/libutil/include/nix/util/types.hh

@@ -12,8 +12,25 @@
 namespace nix {
 
 typedef std::list<std::string> Strings;
-typedef std::map<std::string, std::string> StringMap;
+
-typedef std::map<std::string, std::string> StringPairs;
+/**
+ * Alias to ordered std::string -> std::string map container with transparent comparator.
+ *
+ * Used instead of std::map<std::string, std::string> to use C++14 N3657 [1]
+ * heterogenous lookup consistently across the whole codebase.
+ * Transparent comparators get rid of creation of unnecessary
+ * temporary variables when looking up keys by `std::string_view`
+ * or C-style `const char *` strings.
+ *
+ * [1]: https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2013/n3657.htm
+ */
+using StringMap = std::map<std::string, std::string, std::less<>>;
+/**
+ * Alias to an ordered map of std::string -> std::string. Uses transparent comparator.
+ *
+ * @see StringMap
+ */
+using StringPairs = StringMap;
 
 /**
  * Alias to ordered set container with transparent comparator.

src/libutil/include/nix/util/url.hh

@@ -10,7 +10,7 @@ struct ParsedURL
     std::string scheme;
     std::optional<std::string> authority;
     std::string path;
-    std::map<std::string, std::string> query;
+    StringMap query;
     std::string fragment;
 
     std::string to_string() const;
@@ -30,9 +30,9 @@ MakeError(BadURL, Error);
 std::string percentDecode(std::string_view in);
 std::string percentEncode(std::string_view s, std::string_view keep="");
 
-std::map<std::string, std::string> decodeQuery(const std::string & query);
+StringMap decodeQuery(const std::string & query);
 
-std::string encodeQuery(const std::map<std::string, std::string> & query);
+std::string encodeQuery(const StringMap & query);
 
 ParsedURL parseURL(const std::string & url);
 

src/libutil/include/nix/util/xml-writer.hh

@@ -10,7 +10,7 @@
 namespace nix {
 
 
-typedef std::map<std::string, std::string> XMLAttrs;
+typedef std::map<std::string, std::string, std::less<>> XMLAttrs;
 
 
 class XMLWriter

src/libutil/linux/cgroup.cc

@@ -31,9 +31,9 @@ std::optional<Path> getCgroupFS()
 }
 
 // FIXME: obsolete, check for cgroup2
-std::map<std::string, std::string> getCgroups(const Path & cgroupFile)
+StringMap getCgroups(const Path & cgroupFile)
 {
-    std::map<std::string, std::string> cgroups;
+    StringMap cgroups;
 
     for (auto & line : tokenizeString<std::vector<std::string>>(readFile(cgroupFile), "\n")) {
         static std::regex regex("([0-9]+):([^:]*):(.*)");

src/libutil/linux/include/nix/util/cgroup.hh

@@ -10,7 +10,7 @@ namespace nix {
 
 std::optional<Path> getCgroupFS();
 
-std::map<std::string, std::string> getCgroups(const Path & cgroupFile);
+StringMap getCgroups(const Path & cgroupFile);
 
 struct CgroupStats
 {

src/libutil/url.cc

@@ -70,9 +70,9 @@ std::string percentDecode(std::string_view in)
     return decoded;
 }
 
-std::map<std::string, std::string> decodeQuery(const std::string & query)
+StringMap decodeQuery(const std::string & query)
 {
-    std::map<std::string, std::string> result;
+    StringMap result;
 
     for (const auto & s : tokenizeString<Strings>(query, "&")) {
         auto e = s.find('=');
@@ -108,7 +108,7 @@ std::string percentEncode(std::string_view s, std::string_view keep)
     return res;
 }
 
-std::string encodeQuery(const std::map<std::string, std::string> & ss)
+std::string encodeQuery(const StringMap & ss)
 {
     std::string res;
     bool first = true;

src/nix-channel/nix-channel.cc

@@ -18,7 +18,7 @@
 
 using namespace nix;
 
-typedef std::map<std::string, std::string> Channels;
+typedef StringMap Channels;
 
 static Channels channels;
 static std::filesystem::path channelsList;

src/nix/develop.cc

@@ -55,12 +55,12 @@ struct BuildEnvironment
 
     using Array = std::vector<std::string>;
 
-    using Associative = std::map<std::string, std::string>;
+    using Associative = StringMap;
 
     using Value = std::variant<String, Array, Associative>;
 
     std::map<std::string, Value> vars;
-    std::map<std::string, std::string> bashFunctions;
+    StringMap bashFunctions;
     std::optional<std::pair<std::string, std::string>> structuredAttrs;
 
     static BuildEnvironment fromJSON(const nlohmann::json & json)