Prefix program support

CHANGELOG.md

@@ -1,5 +1,6 @@
 ## Version 1.1 (in progress)
 * Added `app.parse_order()` with original parse order
+* Added `prefix_command()`, which is like `allow_extras` but instantly stops and returns.
 
 ## Version 1.0
 * Cleanup using `clang-tidy` and `clang-format`

README.md

@@ -194,6 +194,7 @@ There are several options that are supported on the main app and subcommands. Th
 * `.parsed()`: True if this subcommand was given on the command line
 * `.set_callback(void() function)`: Set the callback that runs at the end of parsing. The options have already run at this point.
 * `.allow_extras()`: Do not throw an error if extra arguments are left over (Only useful on the main `App`, as that's the one that throws errors).
+* `.prefix_command()`: Like `allow_extras`, but stop immediately on the first unrecognised item. It is ideal for allowing your app to be a "prefix" to calling another app.
 
 ## Configuration file
 

examples/CMakeLists.txt

@@ -18,3 +18,4 @@ add_cli_exe(simple simple.cpp)
 add_cli_exe(subcommands subcommands.cpp)
 add_cli_exe(groups groups.cpp)
 add_cli_exe(inter_argument_order inter_argument_order.cpp)
+add_cli_exe(prefix_command prefix_command.cpp)

examples/prefix_command.cpp

@@ -0,0 +1,32 @@
+#include "CLI/CLI.hpp"
+
+int main(int argc, char **argv) {
+
+    CLI::App app("Prefix command app");
+    app.prefix_command();
+
+    std::vector<int> vals;
+    app.add_option("--vals,-v", vals)
+        ->expected(1);
+
+    std::vector<std::string> more_comms;
+    try {
+        more_comms = app.parse(argc, argv);
+    } catch(const CLI::ParseError &e) {
+        return app.exit(e);
+    }
+
+    std::cout << "Prefix:";
+    for(int v : vals)
+        std::cout << v << ":";
+
+    std::cout << std::endl << "Remaining commands: ";
+
+    // Perfer to loop over from beginning, not "pop" order
+    std::reverse(std::begin(more_comms), std::end(more_comms));
+    for(auto com : more_comms)
+        std::cout << com << " ";
+    std::cout << std::endl;
+
+    return 0;
+}

include/CLI/App.hpp

@@ -57,6 +57,9 @@ class App {
     /// If true, allow extra arguments (ie, don't throw an error).
     bool allow_extras_{false};
 
+    ///  If true, return immediatly on an unrecognised option (implies allow_extras)
+    bool prefix_command_{false};
+
     /// This is a function that runs when complete. Great for subcommands. Can throw.
     std::function<void()> callback_;
 
@@ -152,6 +155,12 @@ class App {
         return this;
     }
 
+    /// Do not parse anything after the first unrecongnised option and return
+    App *prefix_command(bool allow = true) {
+        prefix_command_ = allow;
+        return this;
+    }
+
     /// Ignore case. Subcommand inherit value.
     App *ignore_case(bool value = true) {
         ignore_case_ = value;
@@ -855,7 +864,7 @@ class App {
                     return val.first != detail::Classifer::POSITIONAL_MARK;
                 });
 
-            if(num_left_over > 0 && !allow_extras_)
+            if(num_left_over > 0 && !(allow_extras_ || prefix_command_))
                 throw ExtrasError("[" + detail::rjoin(args, " ") + "]");
         }
     }
@@ -966,7 +975,15 @@ class App {
         else {
             args.pop_back();
             missing()->emplace_back(detail::Classifer::NONE, positional);
+
+            if(prefix_command_) {
+                while(!args.empty()) {
+                    missing()->emplace_back(detail::Classifer::NONE, args.back());
+                    args.pop_back();
+                }
+            }
         }
+
     }
 
     /// Parse a subcommand, modify args and continue

tests/SubcommandTest.cpp

@@ -231,6 +231,19 @@ TEST_F(TApp, BadSubcomSearch) {
     EXPECT_THROW(app.get_subcommand(two), CLI::OptionNotFound);
 }
 
+TEST_F(TApp, PrefixProgram) {
+
+    app.prefix_command();
+
+    app.add_flag("--simple");
+
+    args = {"--simple", "other", "--simple", "--mine"};
+    auto ret_args = run();
+
+    EXPECT_EQ(ret_args, std::vector<std::string>({"--mine", "--simple", "other"}));
+
+}
+
 struct SubcommandProgram : public TApp {
 
     CLI::App *start;