Env validation (#926)

Fixes #925

Author: phlptp

Diff for: README.md

@@ -417,7 +417,8 @@ Before parsing, you can set the following options:
   option. Options can be removed from the excludes list with
   `->remove_excludes(opt)`
 - `->envname(name)`: Gets the value from the environment if present and not
-  passed on the command line.
+  passed on the command line. 🚧 The value must also pass any validators to be
+  used.
 - `->group(name)`: The help group to put the option in. No effect for positional
   options. Defaults to `"Options"`. Options given an empty string will not show
   up in the help print (hidden).

Diff for: book/chapters/options.md

@@ -214,7 +214,7 @@ that to add option modifiers. A full listing of the option modifiers:
 | `->type_size(Nmin,Nmax)`                                | specify that each block of values would consist of between Nmin and Nmax elements                                                                                                                                                                                                                                                                                                                                                                         |
 | `->needs(opt)`                                          | This option requires another option to also be present, opt is an `Option` pointer or a string with the name of the option. Can be removed with `->remove_needs(opt)`                                                                                                                                                                                                                                                                                     |
 | `->excludes(opt)`                                       | This option cannot be given with `opt` present, opt is an `Option` pointer or a string with the name of the option. Can be removed with `->remove_excludes(opt)`                                                                                                                                                                                                                                                                                          |
-| `->envname(name)`                                       | Gets the value from the environment if present and not passed on the command line.                                                                                                                                                                                                                                                                                                                                                                        |
+| `->envname(name)`                                       | Gets the value from the environment if present and not passed on the command line and passes any validators.                                                                                                                                                                                                                                                                                                                                              |
 | `->group(name)`                                         | The help group to put the option in. No effect for positional options. Defaults to `"Options"`. Options given an empty string for the group name will not show up in the help print.                                                                                                                                                                                                                                                                      |
 | `->description(string)`                                 | Set/change the description                                                                                                                                                                                                                                                                                                                                                                                                                                |
 | `->ignore_case()`                                       | Ignore the case on the command line (also works on subcommands, does not affect arguments).                                                                                                                                                                                                                                                                                                                                                               |

Diff for: include/CLI/impl/App_inl.hpp

@@ -1080,7 +1080,11 @@ CLI11_INLINE void App::_process_env() {
         if(opt->count() == 0 && !opt->envname_.empty()) {
             std::string ename_string = detail::get_environment_value(opt->envname_);
             if(!ename_string.empty()) {
-                opt->add_result(ename_string);
+                std::string result = ename_string;
+                result = opt->_validate(result, 0);
+                if(result.empty()) {
+                    opt->add_result(ename_string);
+                }
             }
         }
     }

Diff for: tests/HelpTest.cpp

@@ -10,6 +10,8 @@
 #include "CLI/CLI.hpp"
 #endif
 
+#include "app_helper.hpp"
+
 #include "catch.hpp"
 #include <fstream>
 
@@ -718,6 +720,22 @@ TEST_CASE("THelp: CustomHelp", "[help]") {
     }
 }
 
+TEST_CASE("THelp: HelpSubcommandPriority", "[help]") {
+    CLI::App app{"My prog"};
+
+    app.set_help_flag("-h", "display help and exit");
+
+    auto *sub1 = app.add_subcommand("sub1");
+    std::string someFile = "";
+
+    put_env("SOME_FILE", "NOT_A_FILE");
+    sub1->add_option("-f,--file", someFile)->envname("SOME_FILE")->required()->expected(1)->check(CLI::ExistingFile);
+
+    std::string input{"sub1 -h"};
+    CHECK_THROWS_AS(app.parse(input), CLI::CallForHelp);
+    unset_env("SOME_FILE");
+}
+
 TEST_CASE("THelp: NextLineShouldBeAlignmentInMultilineDescription", "[help]") {
     CLI::App app;
     int i{0};

Diff for: tests/SubcommandTest.cpp

@@ -2138,6 +2138,6 @@ TEST_CASE_METHOD(TApp, "subcommandEnvironmentName", "[subcom]") {
     CHECK_NOTHROW(run());
 
     args = {"sub1", "-v", "111"};
-    CHECK_THROWS_AS(run(), CLI::ValidationError);
+    CHECK_THROWS_AS(run(), CLI::RequiredError);
     unset_env("SOME_FILE");
 }