Adding access to current formatter, using shared pointer to link all formatters

examples/formatter.cpp

@@ -2,6 +2,7 @@
 
 class MyFormatter : public CLI::Formatter {
   public:
+    using Formatter::Formatter;
     std::string make_option_opts(const CLI::Option *) const override { return " OPTION"; }
 };
 
@@ -9,8 +10,8 @@ int main(int argc, char **argv) {
     CLI::App app;
     app.set_help_all_flag("--help-all", "Show all help");
 
-    MyFormatter fmt;
-    fmt.column_width(15);
+    auto fmt = std::make_shared<MyFormatter>();
+    fmt->column_width(15);
     app.formatter(fmt);
 
     app.add_flag("--flag", "This is a flag");

include/CLI/App.hpp

@@ -106,8 +106,8 @@ class App {
     /// A pointer to the help all flag if there is one INHERITABLE
     Option *help_all_ptr_{nullptr};
 
-    /// This is the formatter for help printing. Default provided. INHERITABLE
-    std::function<std::string(const App *, std::string, AppFormatMode)> formatter_{Formatter()};
+    /// This is the formatter for help printing. Default provided. INHERITABLE (same pointer)
+    std::shared_ptr<FormatterBase> formatter_{new Formatter()};
 
     /// The error message printing function INHERITABLE
     std::function<std::string(const App *, const Error &e)> failure_message_ = FailureMessage::simple;
@@ -262,11 +262,17 @@ class App {
     }
 
     /// Set the help formatter
-    App *formatter(std::function<std::string(const App *, std::string, AppFormatMode)> fmt) {
+    App *formatter(std::shared_ptr<FormatterBase> fmt) {
         formatter_ = fmt;
         return this;
     }
 
+    /// Set the help formatter
+    App *formatter(std::function<std::string(const App *, std::string, AppFormatMode)> fmt) {
+        formatter_ = std::make_shared<FormatterLambda>(fmt);
+        return this;
+    }
+
     /// Check to see if this subcommand was parsed, true only if received on command line.
     bool parsed() const { return parsed_; }
 
@@ -1071,13 +1077,16 @@ class App {
         if(!selected_subcommands.empty())
             return selected_subcommands.at(0)->help(prev);
         else
-            return formatter_(this, prev, mode);
+            return formatter_->make_help(this, prev, mode);
     }
 
     ///@}
     /// @name Getters
     ///@{
 
+    /// Access the formatter
+    std::shared_ptr<FormatterBase> get_formatter() const { return formatter_; }
+
     /// Get the app or subcommand description
     std::string get_description() const { return description_; }
 

include/CLI/Formatter.hpp

@@ -113,7 +113,7 @@ inline std::string Formatter::make_footer(const App *app) const {
         return "";
 }
 
-inline std::string Formatter::operator()(const App *app, std::string name, AppFormatMode mode) const {
+inline std::string Formatter::make_help(const App *app, std::string name, AppFormatMode mode) const {
 
     // This immediatly forwards to the make_expanded method. This is done this way so that subcommands can
     // have overridden formatters

include/CLI/FormatterFwd.hpp

@@ -21,10 +21,15 @@ class App;
 enum class AppFormatMode {
     Normal, //< The normal, detailed help
     All,    //< A fully expanded help
-    Sub,    //<  Used when printed as part of expanded subcommand
+    Sub,    //< Used when printed as part of expanded subcommand
 };
 
-class Formatter {
+/// This is the minimum requirements to run a formatter.
+///
+/// A user can subclass this is if they do not care at all
+/// about the structure in CLI::Formatter.
+class FormatterBase {
+  protected:
     /// @name Options
     ///@{
 
@@ -40,9 +45,14 @@ class Formatter {
     ///@{
 
   public:
-    Formatter() = default;
-    Formatter(const Formatter &) = default;
-    Formatter(Formatter &&) = default;
+    FormatterBase() = default;
+    FormatterBase(const FormatterBase &) = default;
+    FormatterBase(FormatterBase &&) = default;
+    virtual ~FormatterBase() = default;
+
+    /// This is the key method that puts together help
+    virtual std::string make_help(const App *, std::string, AppFormatMode) const = 0;
+
     ///@}
     /// @name Setters
     ///@{
@@ -68,6 +78,30 @@ class Formatter {
     /// Get the current column width
     size_t get_column_width() const { return column_width_; }
 
+    ///@}
+};
+
+/// This is a specialty override for lambda functions
+class FormatterLambda final : public FormatterBase {
+    using funct_t = std::function<std::string(const App *, std::string, AppFormatMode)>;
+
+    funct_t lambda_;
+
+  public:
+    explicit FormatterLambda(funct_t funct) : lambda_(funct) {}
+
+    /// This will simply call the lambda function
+    std::string make_help(const App *app, std::string name, AppFormatMode mode) const override {
+        return lambda_(app, name, mode);
+    }
+};
+
+class Formatter : public FormatterBase {
+  public:
+    Formatter() = default;
+    Formatter(const Formatter &) = default;
+    Formatter(Formatter &&) = default;
+
     /// @name Overridables
     ///@{
 
@@ -102,7 +136,7 @@ class Formatter {
     virtual std::string make_usage(const App *app, std::string name) const;
 
     /// This puts everything together
-    virtual std::string operator()(const App *, std::string, AppFormatMode) const;
+    std::string make_help(const App *, std::string, AppFormatMode) const override;
 
     ///@}
     /// @name Options

tests/FormatterTest.cpp

@@ -11,9 +11,28 @@
 using ::testing::HasSubstr;
 using ::testing::Not;
 
+class SimpleFormatter : public CLI::FormatterBase {
+  public:
+    SimpleFormatter() : FormatterBase() {}
+
+    std::string make_help(const CLI::App *, std::string, CLI::AppFormatMode) const override {
+        return "This is really simple";
+    }
+};
+
 TEST(Formatter, Nothing) {
     CLI::App app{"My prog"};
 
+    app.formatter(std::make_shared<SimpleFormatter>());
+
+    std::string help = app.help();
+
+    EXPECT_EQ(help, "This is really simple");
+}
+
+TEST(Formatter, NothingLambda) {
+    CLI::App app{"My prog"};
+
     app.formatter(
         [](const CLI::App *, std::string, CLI::AppFormatMode) { return std::string("This is really simple"); });
 
@@ -25,9 +44,9 @@ TEST(Formatter, Nothing) {
 TEST(Formatter, OptCustomize) {
     CLI::App app{"My prog"};
 
-    CLI::Formatter optfmt;
-    optfmt.column_width(25);
-    optfmt.label("REQUIRED", "(MUST HAVE)");
+    auto optfmt = std::make_shared<CLI::Formatter>();
+    optfmt->column_width(25);
+    optfmt->label("REQUIRED", "(MUST HAVE)");
     app.formatter(optfmt);
 
     int v;
@@ -44,13 +63,33 @@ TEST(Formatter, OptCustomize) {
               "  --opt INT (MUST HAVE)  Something\n");
 }
 
-TEST(Formatter, AptCustomize) {
+TEST(Formatter, OptCustomizeSimple) {
+    CLI::App app{"My prog"};
+
+    app.get_formatter()->column_width(25);
+    app.get_formatter()->label("REQUIRED", "(MUST HAVE)");
+
+    int v;
+    app.add_option("--opt", v, "Something")->required();
+
+    std::string help = app.help();
+
+    EXPECT_THAT(help, HasSubstr("(MUST HAVE)"));
+    EXPECT_EQ(help,
+              "My prog\n"
+              "Usage: [OPTIONS]\n\n"
+              "Options:\n"
+              "  -h,--help              Print this help message and exit\n"
+              "  --opt INT (MUST HAVE)  Something\n");
+}
+
+TEST(Formatter, AppCustomize) {
     CLI::App app{"My prog"};
     app.add_subcommand("subcom1", "This");
 
-    CLI::Formatter appfmt;
-    appfmt.column_width(20);
-    appfmt.label("Usage", "Run");
+    auto appfmt = std::make_shared<CLI::Formatter>();
+    appfmt->column_width(20);
+    appfmt->label("Usage", "Run");
     app.formatter(appfmt);
 
     app.add_subcommand("subcom2", "This");
@@ -66,6 +105,26 @@ TEST(Formatter, AptCustomize) {
               "  subcom2           This\n");
 }
 
+TEST(Formatter, AppCustomizeSimple) {
+    CLI::App app{"My prog"};
+    app.add_subcommand("subcom1", "This");
+
+    app.get_formatter()->column_width(20);
+    app.get_formatter()->label("Usage", "Run");
+
+    app.add_subcommand("subcom2", "This");
+
+    std::string help = app.help();
+    EXPECT_EQ(help,
+              "My prog\n"
+              "Run: [OPTIONS] [SUBCOMMAND]\n\n"
+              "Options:\n"
+              "  -h,--help         Print this help message and exit\n\n"
+              "Subcommands:\n"
+              "  subcom1           This\n"
+              "  subcom2           This\n");
+}
+
 TEST(Formatter, AllSub) {
     CLI::App app{"My prog"};
     CLI::App *sub = app.add_subcommand("subcom", "This");