{scene,shader,image}converter: make output argument treating consistent.

If it's ignored, a warning is printed to catch accidents, but not an
error since it should be possible to just append --info to existing
command line to see what the input is about.

src/Magnum/MeshTools/sceneconverter.cpp

@@ -86,7 +86,7 @@ magnum-sceneconverter [-h|--help] [-I|--importer IMPORTER]
 Arguments:
 
 -   `input` --- input file
--   `output` --- output file, ignored if `--info` is present
+-   `output` --- output file; ignored if `--info` is present
 -   `-h`, `--help` --- display this help message and exit
 -   `-I`, `--importer IMPORTER` --- scene importer plugin (default:
     @ref Trade::AnySceneImporter "AnySceneImporter")
@@ -199,7 +199,7 @@ UnsignedInt namedAttributeId(const Trade::MeshData& mesh, UnsignedInt id) {
 int main(int argc, char** argv) {
     Utility::Arguments args;
     args.addArgument("input").setHelp("input", "input file")
-        .addArgument("output").setHelp("output", "output file, ignored if --info is present")
+        .addArgument("output").setHelp("output", "output file; ignored if --info is present")
         .addOption('I', "importer", "AnySceneImporter").setHelp("importer", "scene importer plugin")
         .addArrayOption('C', "converter").setHelp("converter", "scene converter plugin(s)")
         .addOption("plugin-dir").setHelp("plugin-dir", "override base plugin dir", "DIR")
@@ -241,6 +241,15 @@ save its output; if no -C / --converter is specified, AnySceneConverter is
 used.)")
         .parse(argc, argv);
 
+    /* Generic checks */
+    if(!args.value<Containers::StringView>("output").isEmpty()) {
+        /* Not an error in this case, it should be possible to just append
+           --info to existing command line without having to remove anything.
+           But print a warning at least, it could also be a mistyped option. */
+        if(args.isSet("info"))
+            Warning{} << "Ignoring output file for --info:" << args.value<Containers::StringView>("output");
+    }
+
     PluginManager::Manager<Trade::AbstractImporter> importerManager{
         args.value("plugin-dir").empty() ? std::string{} :
         Utility::Directory::join(args.value("plugin-dir"), Trade::AbstractImporter::pluginSearchPaths()[0])};

src/Magnum/ShaderTools/shaderconverter.cpp

@@ -75,7 +75,7 @@ magnum-shaderconverter [-h|--help] [--validate] [--link]
 Arguments:
 
 -   `input` --- input file(s)
--   `output` --- output file, ignored if `--validate` is present. If neither
+-   `output` --- output file, disallowed for `--validate`. If neither
     `--validate` nor `--link` is present, corresponds to the
     @ref ShaderTools::AbstractConverter::convertFileToFile() function.
 -   `-h`, `--help` --- display this help message and exit
@@ -173,7 +173,7 @@ using namespace Magnum;
 int main(int argc, char** argv) {
     Utility::Arguments args;
     args.addArrayArgument("input").setHelp("input", "input file(s)")
-        .addArgument("output").setHelp("output", "output file, ignored if --validate is present")
+        .addArgument("output").setHelp("output", "output file, disallowed for --validate")
         .addBooleanOption("validate").setHelp("validate", "validate input")
         .addBooleanOption("link").setHelp("link", "link multiple input files together")
         .addArrayOption('C', "converter").setHelp("converter", "shader converter plugin(s)")
@@ -232,9 +232,9 @@ see documentation of a particular converter for more information.)")
         .parse(argc, argv);
 
     /* Generic checks */
-    if(args.isSet("validate")) {
-        if(!args.value<Containers::StringView>("output").isEmpty()) {
-            Error{} << "Output file shouldn't be set for --validate";
+    if(!args.value<Containers::StringView>("output").isEmpty()) {
+        if(args.isSet("validate")) {
+            Error{} << "Output file shouldn't be set for --validate:" << args.value<Containers::StringView>("output");
             return 1;
         }
     }

src/Magnum/Trade/imageconverter.cpp

@@ -75,7 +75,8 @@ magnum-imageconverter [-h|--help] [-I|--importer IMPORTER]
 Arguments:
 
 -   `input` --- input image
--   `output` --- output image, ignored if `--in-place` or `--info` is present
+-   `output` --- output image; ignored if `--info` is present, disallowed for
+    `--in-place`
 -   `-h`, `--help` --- display this help message and exit
 -   `-I`, `--importer IMPORTER` --- image importer plugin (default:
     @ref Trade::AnyImageImporter "AnyImageImporter")
@@ -145,7 +146,7 @@ using namespace Magnum;
 int main(int argc, char** argv) {
     Utility::Arguments args;
     args.addArgument("input").setHelp("input", "input image")
-        .addArgument("output").setHelp("output", "output image, ignored if --in-place or --info is present")
+        .addArgument("output").setHelp("output", "output image; ignored if --info is present, disallowed for --in-place")
         .addOption('I', "importer", "AnyImageImporter").setHelp("importer", "image importer plugin")
         .addOption('C', "converter", "AnyImageConverter").setHelp("converter", "image converter plugin")
         .addOption("plugin-dir").setHelp("plugin-dir", "override base plugin dir", "DIR")
@@ -182,6 +183,20 @@ plugin configuration. If the = character is omitted, it's equivalent to saying
 key=true; configuration subgroups are delimited with /.)")
         .parse(argc, argv);
 
+    /* Generic checks */
+    if(!args.value<Containers::StringView>("output").isEmpty()) {
+        if(args.isSet("in-place")) {
+            Error{} << "Output file shouldn't be set for --in-place:" << args.value<Containers::StringView>("output");
+            return 1;
+        }
+
+        /* Not an error in this case, it should be possible to just append
+           --info to existing command line without having to remove anything.
+           But print a warning at least, it could also be a mistyped option. */
+        if(args.isSet("info"))
+            Warning{} << "Ignoring output file for --info:" << args.value<Containers::StringView>("output");
+    }
+
     PluginManager::Manager<Trade::AbstractImporter> importerManager{
         args.value("plugin-dir").empty() ? std::string{} :
         Utility::Directory::join(args.value("plugin-dir"), Trade::AbstractImporter::pluginSearchPaths()[0])};