*converter: support adding new option keys by prefixing them with +.

Since it's adding new options, it doesn't warn if the key isn't found.

src/Magnum/Implementation/converterUtilities.h

@@ -45,6 +45,12 @@ void setOptions(const Containers::StringView pluginName, Utility::ConfigurationG
         keyValue[0] = keyValue[0].trimmed();
         keyValue[2] = keyValue[2].trimmed();
 
+        bool addValue = false;
+        if(keyValue[0].hasPrefix('+')) {
+            keyValue[0] = keyValue[0].exceptPrefix(1);
+            addValue = true;
+        }
+
         const Containers::Array<Containers::StringView> keyParts = keyValue[0].split('/');
         CORRADE_INTERNAL_ASSERT(!keyParts.isEmpty());
         Utility::ConfigurationGroup* group = &configuration;
@@ -66,7 +72,6 @@ void setOptions(const Containers::StringView pluginName, Utility::ConfigurationG
                 emptySubgroups.insert(subgroup);
             }
             group = subgroup;
-
         }
 
         /* Provide a warning message in case the plugin doesn't define given
@@ -81,7 +86,12 @@ void setOptions(const Containers::StringView pluginName, Utility::ConfigurationG
         if((groupNotRecognized || (!group->hasValue(keyParts.back()) &&
                 /* The warning isn't printed in case a value is added into an
                    empty subgroup, see above */
-                emptySubgroups.find(group) == emptySubgroups.end()
+                emptySubgroups.find(group) == emptySubgroups.end() &&
+                /* The warning also isn't printed in case a new value is added
+                   with `+` instead of modifying an existing one -- e.g. a
+                   plugin can support 0 to n values of a certain key, which
+                   means by default there won't be any */
+                !addValue
             )) && pluginName != anyPluginName)
         {
             Warning{} << "Option" << keyValue[0] << "not recognized by" << pluginName;
@@ -90,10 +100,17 @@ void setOptions(const Containers::StringView pluginName, Utility::ConfigurationG
         /* If the option doesn't have an =, treat it as a boolean flag that's
            set to true. While there's no similar way to do an inverse, it's
            still nicer than causing a fatal error with those. */
-        if(keyValue[1])
-            group->setValue(keyParts.back(), keyValue[2]);
-        else
-            group->setValue(keyParts.back(), true);
+        if(keyValue[1]) {
+            if(addValue)
+                group->addValue(keyParts.back(), keyValue[2]);
+            else
+                group->setValue(keyParts.back(), keyValue[2]);
+        } else {
+            if(addValue)
+                group->addValue(keyParts.back(), true);
+            else
+                group->setValue(keyParts.back(), true);
+        }
     }
 }
 

src/Magnum/SceneTools/sceneconverter.cpp

@@ -284,7 +284,8 @@ with `--info-meshes` will print how many objects reference given mesh).
 The `-i`, `-c` and `-m` arguments accept a comma-separated list of key/value
 pairs to set in the importer / converter plugin configuration. If the `=`
 character is omitted, it's equivalent to saying `key=true`; configuration
-subgroups are delimited with `/`.
+subgroups are delimited with `/`. Prefix the key with `+` to add new options or
+multiple options of the same name.
 
 It's possible to specify the `-C` option (and correspondingly also `-c`)
 multiple times in order to chain more converters together. All converters in
@@ -487,7 +488,8 @@ will also list reference count (for example, --info-scenes together with
 The -i, -c and -m arguments accept a comma-separated list of key/value
 pairs to set in the importer / converter plugin configuration. If the =
 character is omitted, it's equivalent to saying key=true; configuration
-subgroups are delimited with /.
+subgroups are delimited with /. Prefix the key with + to add new options or
+multiple options of the same name.
 
 It's possible to specify the -C option (and correspondingly also -c) multiple
 times in order to chain more scene converters together. All converters in the

src/Magnum/ShaderTools/shaderconverter.cpp

@@ -153,12 +153,15 @@ save it to `output`.
 The `-c` / `--converter-options` argument accept a comma-separated list of
 key/value pairs to set in the converter plugin configuration. If the `=`
 character is omitted, it's equivalent to saying `key=true`; configuration
-subgroups are delimited with `/`. It's possible to specify the `-C` /
-`--converter` option (and correspondingly also `-c` / `--converter-options`,
-`--input-format`, `--output-format`, `--input-version` and `--output-version`)
-multiple times in order to chain more converters together. All converters in
-the chain have to support the @ref ShaderTools::ConverterFeature::ConvertData
-feature, if there's just one converter it's enough for it to support
+subgroups are delimited with `/`. Prefix the key with `+` to add new options or
+multiple options of the same name.
+
+It's possible to specify the `-C` / `--converter` option (and correspondingly
+also `-c` / `--converter-options`, `--input-format`, `--output-format`,
+`--input-version` and `--output-version`) multiple times in order to chain more
+converters together. All converters in the chain have to support the
+@ref ShaderTools::ConverterFeature::ConvertData feature, if there's just one
+converter it's enough for it to support
 @ref ShaderTools::ConverterFeature::ConvertFile. If no `-C` / `--converter` is
 specified, @ref ShaderTools::AnyConverter "AnyShaderConverter" is used.
 
@@ -284,13 +287,15 @@ specified, the utility will convert the input file using (one or more) passed
 The -c / --converter-options argument accept a comma-separated list of
 key/value pairs to set in the converter plugin configuration. If the =
 character is omitted, it's equivalent to saying key=true; configuration
-subgroups are delimited with /. It's possible to specify the -C / --converter
-option (and correspondingly also -c / --converter-options, --input-format,
---output-format, --input-version and --output-version) multiple times in order
-to chain more converters together. All converters in the chain have to support
-the ConvertData feature, if there's just one converter it's enough for it to
-support ConvertFile. If no -C / --converter is specified, AnyShaderConverter is
-used.
+subgroups are delimited with /. Prefix the key with + to add new options or
+multiple options of the same name.
+
+It's possible to specify the -C / --converter option (and correspondingly also
+-c / --converter-options, --input-format, --output-format, --input-version and
+--output-version) multiple times in order to chain more converters together.
+All converters in the chain have to support the ConvertData feature, if there's
+just one converter it's enough for it to support ConvertFile. If no -C /
+--converter is specified, AnyShaderConverter is used.
 
 The -D / --define, -U / --undefine, -O / --optimize, -g / --debug-info, -E /
 --preprocess-only arguments apply only to the first converter. Split the

src/Magnum/Test/ConverterUtilitiesTest.cpp

@@ -25,6 +25,7 @@
 
 #include <sstream>
 #include <Corrade/TestSuite/Tester.h>
+#include <Corrade/TestSuite/Compare/String.h>
 #include <Corrade/Utility/Configuration.h>
 #include <Corrade/Utility/DebugStl.h>
 
@@ -39,7 +40,7 @@ struct ConverterUtilitiesTest: TestSuite::Tester {
 };
 
 const struct {
-    const char* name;
+    TestSuite::TestCaseDescriptionSourceLocation name;
     const char* config;
     const char* options;
     const char* anyPluginName;
@@ -185,6 +186,64 @@ notFound=value
 )",
         /* The trailing space is there because the plugin name is empty */
         "Option notFound not recognized by \n"},
+
+    /* Adding new unrecognized options to existing groups doesn't warn */
+    {"add an unrecognized option that doesn't exist yet", R"([configuration]
+option=
+another=
+)",
+        "+yetanother=value", "AnyPlugin", R"([configuration]
+option=
+another=
+yetanother=value
+)", nullptr},
+    {"add an option that exists already", R"([configuration]
+option=
+another=
+)",
+        "+option=value", "AnyPlugin", R"([configuration]
+option=
+another=
+option=value
+)", nullptr},
+    {"two options, add second with implicit true", R"([configuration]
+option=
+another=
+)",
+        "option=value,+yetanother", "AnyPlugin", R"([configuration]
+option=value
+another=
+yetanother=true
+)", nullptr},
+    {"add an option to an existing subgroup", R"([configuration]
+option=
+[configuration/group]
+option=
+another=
+)",
+        "+group/option=value", "AnyPlugin", R"([configuration]
+option=
+[configuration/group]
+option=
+another=
+option=value
+)", nullptr},
+    {"add an option to an unrecognized subgroup", R"([configuration]
+option=
+[configuration/group]
+option=
+another=
+)",
+        "+notFound/option=value", "AnyPlugin", R"([configuration]
+option=
+[configuration/group]
+option=
+another=
+[configuration/notFound]
+option=value
+)",
+    /* The trailing space is there because the plugin name is empty */
+    "Option notFound/option not recognized by \n"},
 };
 
 ConverterUtilitiesTest::ConverterUtilitiesTest() {
@@ -219,7 +278,9 @@ void ConverterUtilitiesTest::setOptions() {
     CORRADE_COMPARE(conf.group("configuration")->configuration(), &conf);
     std::ostringstream out;
     conf.save(out);
-    CORRADE_COMPARE(out.str(), data.expectedConfig);
+    CORRADE_COMPARE_AS(out.str(),
+        data.expectedConfig,
+        TestSuite::Compare::String);
 }
 
 }}}

src/Magnum/Trade/imageconverter.cpp

@@ -272,7 +272,8 @@ The `-i` / `--importer-options` and `-c` / `--converter-options` arguments
 accept a comma-separated list of key/value pairs to set in the importer /
 converter plugin configuration. If the `=` character is omitted, it's
 equivalent to saying `key=true`; configuration subgroups are delimited with
-`/`.
+`/`. Prefix the key with `+` to add new options or multiple options of the same
+name.
 
 It's possible to specify the `-C` / `--converter` option (and correspondingly
 also `-c` / `--converter-options`) multiple times in order to chain more
@@ -438,7 +439,8 @@ read but no conversion is done and output file doesn't need to be specified.
 The -i / --importer-options and -c / --converter-options arguments accept a
 comma-separated list of key/value pairs to set in the importer / converter
 plugin configuration. If the = character is omitted, it's equivalent to saying
-key=true; configuration subgroups are delimited with /.
+key=true; configuration subgroups are delimited with /. Prefix the key with +
+to add new options or multiple options of the same name.
 
 It's possible to specify the -C / --converter option (and correspondingly also
 -c / --converter-options) multiple times in order to chain more converters