return exit code from app::run and main

We want to have exit codes from the main function in case of errors.
The exit codes are returned from app::run so we can unit test the
correct behavior.

.clang-tidy

@@ -1,5 +1,5 @@
 ---
-Checks: '*,-fuchsia-*,-google-*,-zircon-*,-abseil-*,-modernize-use-trailing-return-type,-llvm*'
+Checks: '*,-fuchsia-*,-google-*,-zircon-*,-abseil-*,-modernize-use-trailing-return-type,-llvm*,-altera*'
 WarningsAsErrors: ''
 HeaderFilterRegex: ''
 FormatStyle: none

behave/steps/fix_cli.py

@@ -4,6 +4,9 @@
 fix_executable = '../cmake-build-debug/bin/fix'
 
 
+def assert_equals(a, b):
+    assert(a == b), "{} should equal {}!".format(a, b)
+
 def _start_fix_with_args(context, args):
     context.fix = pexpect.spawn(fix_executable, args=args)
 
@@ -42,4 +45,4 @@ def check_commands(context):
 
 @then(u'terminates with exit code {ec:d}')
 def check_exit_code(context, ec):
-    assert (context.fix.wait() == ec)
+    assert_equals(context.fix.wait(), ec)

src/CMakeLists.txt

@@ -10,4 +10,3 @@ target_link_libraries(
     project_warnings
     fix_cli
 )
-

src/fix_cli/app.cpp

@@ -21,5 +21,9 @@ app::app(std::ostream &out)
   out << USAGE;
 }
 
-void app::run(const std::vector<std::string_view>& /*args*/) { //NOLINT
+auto app::run(const std::vector<std::string_view>& args) -> int { // NOLINT
+  if (args.empty()) {
+    return EXIT_FAILURE;
+  }
+  return EXIT_SUCCESS;
 }

src/fix_cli/app.hpp

@@ -11,7 +11,7 @@ class app {
 public:
   explicit app(std::ostream &out);
 
-  void run(std::vector<std::string_view> const &);
+  auto run(std::vector<std::string_view> const &) -> int;
 };
 
 }

src/main.cpp

@@ -4,6 +4,6 @@
 
 int main(int argc, char* argv[]) {
   fix::cli::app app{std::cout};
-  const std::vector<std::string_view> args(argv, std::next(argv, argc));
-  app.run(args);
+  const std::vector<std::string_view> args(std::next(argv), std::next(argv, argc));
+  return app.run(args);
 }

test/fix_cli/app_test.cpp

@@ -23,11 +23,11 @@ TEST_CASE("Prints usage and commands...") {
   fix::cli::app app{out};
 
   SECTION("... when run without commands") {
-    app.run({});
+    CHECK(app.run({}) == EXIT_FAILURE);
   }SECTION("... when run with --help option") {
-    app.run({"--help"});
+    CHECK(app.run({"--help"}) == EXIT_SUCCESS);
   }SECTION("... when run with -h option") {
-    app.run({"-h"});
+    CHECK(app.run({"-h"}) == EXIT_SUCCESS);
   }
 
   CHECK(out.str() == USAGE);