Subcommand fallthrough (#1073)

Add modifier for subcommands to restrict subcommands falling through to
parent.
This will resolve #1022

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

.github/actions/quick_cmake/action.yml

@@ -13,7 +13,7 @@ runs:
   using: composite
   steps:
     - name: CMake ${{ inputs.cmake-version }}
-      uses: jwlawson/actions-setup-cmake@v1.14
+      uses: jwlawson/actions-setup-cmake@v2.0.2
       with:
         cmake-version: "${{ inputs.cmake-version }}"
     - run: |

.github/workflows/tests.yml

@@ -292,10 +292,10 @@ jobs:
           cmake-version: "3.13"
         if: success() || failure()
 
-      - name: Check CMake 3.14
+      - name: Check CMake 3.14.7
         uses: ./.github/actions/quick_cmake
         with:
-          cmake-version: "3.14"
+          cmake-version: "3.14.7"
           args: -DCLI11_SANITIZERS=ON -DCLI11_BUILD_EXAMPLES_JSON=ON
         if: success() || failure()
 
@@ -387,6 +387,6 @@ jobs:
       - name: Check CMake 3.28 (full)
         uses: ./.github/actions/quick_cmake
         with:
-          cmake-version: "3.28"
+          cmake-version: "3.28.X"
           args: -DCLI11_SANITIZERS=ON -DCLI11_BUILD_EXAMPLES_JSON=ON
         if: success() || failure()

README.md

@@ -905,10 +905,15 @@ option_groups. These are:
   options are specified in the `add_option` calls or the ability to process
   options in the form of `-s --long --file=file_name.ext`.
 - `.fallthrough()`: Allow extra unmatched options and positionals to "fall
-  through" and be matched on a parent option. Subcommands always are allowed to
-  "fall through" as in they will first attempt to match on the current
+  through" and be matched on a parent option. Subcommands by default are allowed
+  to "fall through" as in they will first attempt to match on the current
   subcommand and if they fail will progressively check parents for matching
-  subcommands.
+  subcommands. This can be disabled through `subcommand_fallthrough(false)` 🚧.
+- `.subcommand_fallthrough()`: 🚧 Allow subcommands to "fall through" and be
+  matched on a parent option. Disabling this prevents additional subcommands at
+  the same level from being matched. It can be useful in certain circumstances
+  where there might be ambiguity between subcommands and positionals. The
+  default is true.
 - `.configurable()`: Allow the subcommand to be triggered from a configuration
   file. By default subcommand options in a configuration file do not trigger a
   subcommand but will just update default values.

book/chapters/subcommands.md

@@ -132,7 +132,21 @@ gitbook:code $ ./my_program my_model_1 --model_flag --shared_flag
 ```
 
 Here, `--shared_flag` was set on the main app, and on the command line it "falls
-through" `my_model_1` to match on the main app.
+through" `my_model_1` to match on the main app. This is set through
+`->fallthrough()` on a subcommand.
+
+#### Subcommand fallthrough
+
+Subcommand fallthrough allows additional subcommands to be triggered after the
+first subcommand. By default subcommand fallthrough is enabled, but it can be
+turned off through `->subcommand_fallthrough(false)` on a subcommand. This will
+prevent additional subcommands at the same inheritance level from triggering,
+the strings would then be treated as positional values. As a technical note if
+fallthrough is enabled but subcommand fallthrough disabled (this is not the
+default in both cases), then subcommands on grandparents can still be triggered
+from the grandchild subcommand, unless subcommand fallthrough is also disabled
+on the parent. This is an unusual circumstance but may arise in some very
+particular situations.
 
 ### Prefix command
 

include/CLI/App.hpp

@@ -224,9 +224,13 @@ class App {
     /// If true, the program should ignore underscores INHERITABLE
     bool ignore_underscore_{false};
 
-    /// Allow subcommand fallthrough, so that parent commands can collect commands after subcommand.  INHERITABLE
+    /// Allow options or other arguments to fallthrough, so that parent commands can collect options after subcommand.
+    /// INHERITABLE
     bool fallthrough_{false};
 
+    /// Allow subcommands to fallthrough, so that parent commands can trigger other subcommands after subcommand.
+    bool subcommand_fallthrough_{true};
+
     /// Allow '/' for options for Windows like options. Defaults to true on Windows, false otherwise. INHERITABLE
     bool allow_windows_style_options_{
 #ifdef _WIN32
@@ -828,13 +832,19 @@ class App {
         return this;
     }
 
-    /// Stop subcommand fallthrough, so that parent commands cannot collect commands after subcommand.
+    /// Set fallthrough, set to true so that options will fallthrough to parent if not recognized in a subcommand
     /// Default from parent, usually set on parent.
     App *fallthrough(bool value = true) {
         fallthrough_ = value;
         return this;
     }
 
+    /// Set subcommand fallthrough, set to true so that subcommands on parents are recognized
+    App *subcommand_fallthrough(bool value = true) {
+        subcommand_fallthrough_ = value;
+        return this;
+    }
+
     /// Check to see if this subcommand was parsed, true only if received on command line.
     /// This allows the subcommand to be directly checked.
     explicit operator bool() const { return parsed_ > 0; }
@@ -1084,6 +1094,9 @@ class App {
     /// Check the status of fallthrough
     CLI11_NODISCARD bool get_fallthrough() const { return fallthrough_; }
 
+    /// Check the status of subcommand fallthrough
+    CLI11_NODISCARD bool get_subcommand_fallthrough() const { return subcommand_fallthrough_; }
+
     /// Check the status of the allow windows style options
     CLI11_NODISCARD bool get_allow_windows_style_options() const { return allow_windows_style_options_; }
 

include/CLI/impl/App_inl.hpp

@@ -1038,15 +1038,19 @@ CLI11_INLINE void App::run_callback(bool final_mode, bool suppress_final_callbac
 
 CLI11_NODISCARD CLI11_INLINE bool App::_valid_subcommand(const std::string &current, bool ignore_used) const {
     // Don't match if max has been reached - but still check parents
-    if(require_subcommand_max_ != 0 && parsed_subcommands_.size() >= require_subcommand_max_) {
+    if(require_subcommand_max_ != 0 && parsed_subcommands_.size() >= require_subcommand_max_ &&
+       subcommand_fallthrough_) {
         return parent_ != nullptr && parent_->_valid_subcommand(current, ignore_used);
     }
     auto *com = _find_subcommand(current, true, ignore_used);
     if(com != nullptr) {
         return true;
     }
     // Check parent if exists, else return false
-    return parent_ != nullptr && parent_->_valid_subcommand(current, ignore_used);
+    if(subcommand_fallthrough_) {
+        return parent_ != nullptr && parent_->_valid_subcommand(current, ignore_used);
+    }
+    return false;
 }
 
 CLI11_NODISCARD CLI11_INLINE detail::Classifier App::_recognize(const std::string &current,
@@ -1743,9 +1747,9 @@ CLI11_INLINE bool App::_parse_positional(std::vector<std::string> &args, bool ha
         }
     }
     // let the parent deal with it if possible
-    if(parent_ != nullptr && fallthrough_)
+    if(parent_ != nullptr && fallthrough_) {
         return _get_fallthrough_parent()->_parse_positional(args, static_cast<bool>(parse_complete_callback_));
-
+    }
     /// Try to find a local subcommand that is repeated
     auto *com = _find_subcommand(args.back(), true, false);
     if(com != nullptr && (require_subcommand_max_ == 0 || require_subcommand_max_ > parsed_subcommands_.size())) {
@@ -1756,15 +1760,16 @@ CLI11_INLINE bool App::_parse_positional(std::vector<std::string> &args, bool ha
         com->_parse(args);
         return true;
     }
-    /// now try one last gasp at subcommands that have been executed before, go to root app and try to find a
-    /// subcommand in a broader way, if one exists let the parent deal with it
-    auto *parent_app = (parent_ != nullptr) ? _get_fallthrough_parent() : this;
-    com = parent_app->_find_subcommand(args.back(), true, false);
-    if(com != nullptr && (com->parent_->require_subcommand_max_ == 0 ||
-                          com->parent_->require_subcommand_max_ > com->parent_->parsed_subcommands_.size())) {
-        return false;
+    if(subcommand_fallthrough_) {
+        /// now try one last gasp at subcommands that have been executed before, go to root app and try to find a
+        /// subcommand in a broader way, if one exists let the parent deal with it
+        auto *parent_app = (parent_ != nullptr) ? _get_fallthrough_parent() : this;
+        com = parent_app->_find_subcommand(args.back(), true, false);
+        if(com != nullptr && (com->parent_->require_subcommand_max_ == 0 ||
+                              com->parent_->require_subcommand_max_ > com->parent_->parsed_subcommands_.size())) {
+            return false;
+        }
     }
-
     if(positionals_at_end_) {
         throw CLI::ExtrasError(name_, args);
     }

tests/CMakeLists.txt

@@ -4,7 +4,7 @@ if(CLI11_SANITIZERS AND ${CMAKE_VERSION} VERSION_GREATER "3.13.0")
     sanitizers
     GIT_REPOSITORY https://github.com/arsenm/sanitizers-cmake.git
     GIT_SHALLOW 1
-    GIT_TAG 3f0542e)
+    GIT_TAG 0573e2e)
 
   FetchContent_GetProperties(sanitizers)
 

tests/SubcommandTest.cpp

@@ -719,12 +719,25 @@ TEST_CASE_METHOD(TApp, "Required1SubCom", "[subcom]") {
     CHECK_THROWS_AS(run(), CLI::RequiredError);
 
     args = {"sub1"};
-    run();
+    CHECK_NOTHROW(run());
 
     args = {"sub1", "sub2"};
     CHECK_THROWS_AS(run(), CLI::ExtrasError);
 }
 
+TEST_CASE_METHOD(TApp, "subcomNoSubComfallthrough", "[subcom]") {
+    auto *sub1 = app.add_subcommand("sub1");
+    std::vector<std::string> pos;
+    sub1->add_option("args", pos);
+    app.add_subcommand("sub2");
+    app.add_subcommand("sub3");
+    sub1->subcommand_fallthrough(false);
+    CHECK_FALSE(sub1->get_subcommand_fallthrough());
+    args = {"sub1", "sub2", "sub3"};
+    run();
+    CHECK(pos.size() == 2);
+}
+
 TEST_CASE_METHOD(TApp, "BadSubcommandSearch", "[subcom]") {
 
     auto *one = app.add_subcommand("one");