Move target type handling to an enum for refactor

CMakeLists.txt

@@ -24,6 +24,7 @@ set(cmkrlib_SOURCES
 	src/cmkrlib/gen.cpp
 	src/cmkrlib/help.cpp
 	src/cmkrlib/cmake.hpp
+	src/cmkrlib/enum_helper.hpp
 	src/cmkrlib/fs.hpp
 	include/args.h
 	include/build.h

src/cmkrlib/cmake.cpp

@@ -17,6 +17,26 @@ std::vector<std::string> to_string_vec(const std::vector<TomlBasicValue> &vals)
         temp.push_back(val.as_string());
     return temp;
 }
+
+template <typename EnumType>
+EnumType to_enum(const std::string &str, const std::string &help_name) {
+    EnumType value;
+    try {
+        std::stringstream ss(str);
+        ss >> enumFromString(value);
+    } catch (std::invalid_argument &) {
+        std::string supported;
+        for (const auto &s : enumStrings<EnumType>::data) {
+            if (!supported.empty()) {
+                supported += ", ";
+            }
+            supported += s;
+        }
+        throw std::runtime_error("Unknown " + help_name + "'" + str + "'! Supported types are: " + supported);
+    }
+    return value;
+}
+
 } // namespace detail
 
 CMake::CMake(const std::string &path, bool build) {
@@ -180,7 +200,7 @@ CMake::CMake(const std::string &path, bool build) {
                 const auto &t = itr.second;
                 Target target;
                 target.name = itr.first;
-                target.type = toml::find(t, "type").as_string();
+                target.type = detail::to_enum<TargetType>(toml::find(t, "type").as_string(), "target type");
 
                 target.sources = detail::to_string_vec(toml::find(t, "sources").as_array());
 

src/cmkrlib/cmake.hpp

@@ -1,11 +1,12 @@
 #pragma once
 
+#include "enum_helper.hpp"
 #include <map>
+#include <mpark/variant.hpp>
 #include <stdexcept>
 #include <string>
-#include <vector>
-#include <mpark/variant.hpp>
 #include <tsl/ordered_map.h>
+#include <vector>
 
 namespace cmkr {
 namespace cmake {
@@ -31,9 +32,18 @@ struct Package {
     std::vector<std::string> components;
 };
 
+enum TargetType {
+    target_executable,
+    target_library,
+    target_shared,
+    target_static,
+    target_interface,
+    target_custom,
+};
+
 struct Target {
     std::string name;
-    std::string type;
+    TargetType type;
 
     // https://cmake.org/cmake/help/latest/manual/cmake-commands.7.html#project-commands
     std::vector<std::string> compile_definitions;
@@ -45,7 +55,7 @@ struct Target {
     std::vector<std::string> link_options;
     std::vector<std::string> precompile_headers;
     std::vector<std::string> sources;
-    
+
     std::string alias;
     tsl::ordered_map<std::string, std::string> properties;
 
@@ -97,4 +107,7 @@ struct CMake {
 };
 
 } // namespace cmake
-} // namespace cmkr
+} // namespace cmkr
+
+template <>
+const char *enumStrings<cmkr::cmake::TargetType>::data[] = {"executable", "library", "shared", "static", "internface", "custom"};

src/cmkrlib/enum_helper.hpp

@@ -0,0 +1,69 @@
+// https://codereview.stackexchange.com/a/14315
+
+#include <algorithm>
+#include <iostream>
+#include <sstream>
+#include <string>
+
+// This is the type that will hold all the strings.
+// Each enumeration type will declare its own specialization.
+// Any enum that does not have a specialization will generate a compiler error
+// indicating that there is no definition of this variable (as there should be
+// be no definition of a generic version).
+template <typename T>
+struct enumStrings {
+    static char const *data[];
+};
+
+// This is a utility type.
+// Created automatically. Should not be used directly.
+template <typename T>
+struct enumRefHolder {
+    T &enumVal;
+    enumRefHolder(T &enumVal) : enumVal(enumVal) {}
+};
+template <typename T>
+struct enumConstRefHolder {
+    T const &enumVal;
+    enumConstRefHolder(T const &enumVal) : enumVal(enumVal) {}
+};
+
+// The next two functions do the actual work of reading/writing an
+// enum as a string.
+template <typename T>
+std::ostream &operator<<(std::ostream &str, enumConstRefHolder<T> const &data) {
+    return str << enumStrings<T>::data[data.enumVal];
+}
+
+template <typename T>
+std::istream &operator>>(std::istream &str, enumRefHolder<T> const &data) {
+    std::string value;
+    str >> value;
+
+    // These two can be made easier to read in C++11
+    // using std::begin() and std::end()
+    //
+    static auto begin = std::begin(enumStrings<T>::data);
+    static auto end = std::end(enumStrings<T>::data);
+
+    auto find = std::find(begin, end, value);
+    if (find != end) {
+        data.enumVal = static_cast<T>(std::distance(begin, find));
+    } else {
+        throw std::invalid_argument("");
+    }
+    return str;
+}
+
+// This is the public interface:
+// use the ability of function to deduce their template type without
+// being explicitly told to create the correct type of enumRefHolder<T>
+template <typename T>
+enumConstRefHolder<T> enumToString(T const &e) {
+    return enumConstRefHolder<T>(e);
+}
+
+template <typename T>
+enumRefHolder<T> enumFromString(T &e) {
+    return enumRefHolder<T>(e);
+}

src/cmkrlib/gen.cpp

@@ -233,6 +233,8 @@ int generate_cmake(const char *path, bool root) {
 
         int indent = 0;
         auto cmd = [&ss, &indent](const std::string &command) {
+            if (command.empty())
+                throw std::invalid_argument("command cannot be empty");
             if (command == "if") {
                 indent++;
                 return Command(ss, indent - 1, command);
@@ -432,24 +434,16 @@ int generate_cmake(const char *path, bool root) {
 
         if (!cmake.targets.empty()) {
             for (const auto &target : cmake.targets) {
-                std::string add_command;
-                std::string target_type;
-                std::string target_scope;
-                if (target.type == "executable") {
-                    add_command = "add_executable";
-                    target_type = "";
-                    target_scope = "PRIVATE";
-                } else if (target.type == "shared" || target.type == "static" || target.type == "interface") {
-                    add_command = "add_library";
-                    target_type = detail::to_upper(target.type);
-                    target_scope = target_type == "INTERFACE" ? target_type : "PUBLIC";
-                } else if (target.type == "library") {
-                    add_command = "add_library";
-                    target_type = "";
-                    target_scope = "PUBLIC";
-                } else {
-                    throw std::runtime_error("Unknown target type " + target.type +
-                                             "! Supported types are: executable, library, shared, static, interface");
+                if (!target.cmake_before.empty()) {
+                    ss << tolf(target.cmake_before) << "\n\n";
+                }
+
+                if (!target.include_before.empty()) {
+                    for (const auto &file : target.include_before) {
+                        // TODO: warn/error if file doesn't exist?
+                        cmd("include")(file);
+                    }
+                    endl();
                 }
 
                 if (!target.sources.empty()) {
@@ -464,22 +458,49 @@ int generate_cmake(const char *path, bool root) {
                     if (sources.empty()) {
                         throw std::runtime_error(target.name + " sources wildcard found 0 files");
                     }
-                    if (target.type != "interface") {
+                    if (target.type != cmake::target_interface) {
                         sources.push_back("cmake.toml");
                     }
                     cmd("set")(target.name + "_SOURCES", sources).endl();
                 }
 
-                if (!target.cmake_before.empty()) {
-                    ss << tolf(target.cmake_before) << "\n\n";
-                }
-
-                if (!target.include_before.empty()) {
-                    for (const auto &file : target.include_before) {
-                        // TODO: warn/error if file doesn't exist?
-                        cmd("include")(file);
-                    }
-                    endl();
+                std::string add_command;
+                std::string target_type;
+                std::string target_scope;
+                switch (target.type) {
+                case cmake::target_executable:
+                    add_command = "add_executable";
+                    target_type = "";
+                    target_scope = "PRIVATE";
+                    break;
+                case cmake::target_library:
+                    add_command = "add_library";
+                    target_type = "";
+                    target_scope = "PUBLIC";
+                    break;
+                case cmake::target_shared:
+                    add_command = "add_library";
+                    target_type = "SHARED";
+                    target_scope = "PUBLIC";
+                    break;
+                case cmake::target_static:
+                    add_command = "add_library";
+                    target_type = "STATIC";
+                    target_scope = "PUBLIC";
+                    break;
+                case cmake::target_interface:
+                    add_command = "add_library";
+                    target_type = "INTERFACE";
+                    target_scope = "INTERFACE";
+                    break;
+                case cmake::target_custom:
+                    // TODO: add proper support
+                    add_command = "add_custom_target";
+                    target_type = "";
+                    target_scope = "PUBLIC";
+                    break;
+                default:
+                    assert("Unimplemented enum value" && false);
                 }
 
                 cmd(add_command)(target.name, target_type, "${" + target.name + "_SOURCES}").endl();