Show (short) list of possible enum values when an invalid value is encountered (resolves #1318)

All enum errors have (hopefully) been changed to a luax_enumerror, which has a
fixed error message. If additionally a list of valid options is passed, it
lists that in the error message. For every enum error with few options I've
implemented this using a getConstants call.

This solution has been designed specifically to reduce the number of template
instantiations (as I've been told that was a concern). All new template code
happens in places where there already was an instantiation of the relevant
StringMap. Of course there is still std::vector<std::string>...

--HG--
branch : minor

src/modules/data/Compressor.cpp

@@ -379,6 +379,11 @@ bool Compressor::getConstant(Format in, const char *&out)
 	return formatNames.find(in, out);
 }
 
+std::vector<std::string> Compressor::getConstants(Format)
+{
+	return formatNames.getNames();
+}
+
 StringMap<Compressor::Format, Compressor::FORMAT_MAX_ENUM>::Entry Compressor::formatEntries[] =
 {
 	{ "lz4",  FORMAT_LZ4  },

src/modules/data/Compressor.h

@@ -87,6 +87,7 @@ public:
 
 	static bool getConstant(const char *in, Format &out);
 	static bool getConstant(Format in, const char *&out);
+	static std::vector<std::string> getConstants(Format);
 
 protected:
 

src/modules/data/DataModule.cpp

@@ -263,5 +263,10 @@ bool getConstant(EncodeFormat in, const char *&out)
 	return encoders.find(in, out);
 }
 
+std::vector<std::string> getConstants(EncodeFormat)
+{
+	return encoders.getNames();
+}
+
 } // data
 } // love

src/modules/data/DataModule.h

@@ -96,6 +96,7 @@ void hash(HashFunction::Function function, const char *input, uint64_t size, Has
 
 bool getConstant(const char *in, EncodeFormat &out);
 bool getConstant(EncodeFormat in, const char *&out);
+std::vector<std::string> getConstants(EncodeFormat);
 
 
 class DataModule : public Module

src/modules/data/HashFunction.cpp

@@ -619,6 +619,10 @@ bool HashFunction::getConstant(const Function &in, const char *&out)
 {
 	return functionNames.find(in, out);
 }
+std::vector<std::string> HashFunction::getConstants(Function)
+{
+	return functionNames.getNames();
+}
 
 StringMap<HashFunction::Function, HashFunction::FUNCTION_MAX_ENUM>::Entry HashFunction::functionEntries[] =
 {

src/modules/data/HashFunction.h

@@ -80,6 +80,7 @@ public:
 
 	static bool getConstant(const char *in, Function &out);
 	static bool getConstant(const Function &in, const char *&out);
+	static std::vector<std::string> getConstants(Function);
 
 protected:
 

src/modules/data/wrap_CompressedData.cpp

@@ -47,7 +47,7 @@ int w_CompressedData_getFormat(lua_State *L)
 
 	const char *fname = nullptr;
 	if (!Compressor::getConstant(t->getFormat(), fname))
-		return luaL_error(L, "Unknown compressed data format.");
+		return luax_enumerror(L, "compressed data format", Compressor::getConstants(Compressor::FORMAT_MAX_ENUM), fname);
 
 	lua_pushstring(L, fname);
 	return 1;

src/modules/data/wrap_DataModule.cpp

@@ -107,7 +107,7 @@ int w_compress(lua_State *L)
 	Compressor::Format format = Compressor::FORMAT_LZ4;
 
 	if (!Compressor::getConstant(fstr, format))
-		return luaL_error(L, "Invalid compressed data format: %s", fstr);
+		return luax_enumerror(L, "compressed data format", Compressor::getConstants(format), fstr);
 
 	int level = (int) luaL_optinteger(L, 3, -1);
 
@@ -146,7 +146,7 @@ int w_decompress(lua_State *L)
 		const char *fstr = luaL_checkstring(L, 1);
 
 		if (!Compressor::getConstant(fstr, format))
-			return luaL_error(L, "Invalid compressed data format: %s", fstr);
+			return luax_enumerror(L, "compressed data format", Compressor::getConstants(format), fstr);
 
 		size_t compressedsize = 0;
 		const char *cbytes = nullptr;
@@ -174,7 +174,7 @@ int w_encode(lua_State *L)
 	const char *formatstr = luaL_checkstring(L, 1);
 	EncodeFormat format;
 	if (!getConstant(formatstr, format))
-		return luaL_error(L, "Invalid encode format: %s", formatstr);
+		return luax_enumerror(L, "encode format", getConstants(format), formatstr);
 
 	size_t srclen = 0;
 	const char *src = nullptr;
@@ -208,7 +208,7 @@ int w_decode(lua_State *L)
 	const char *formatstr = luaL_checkstring(L, 1);
 	EncodeFormat format;
 	if (!getConstant(formatstr, format))
-		return luaL_error(L, "Invalid decode format: %s", formatstr);
+		return luax_enumerror(L, "decode format", getConstants(format), formatstr);
 
 	size_t srclen = 0;
 	const char *src = nullptr;
@@ -240,7 +240,7 @@ int w_hash(lua_State *L)
 	const char *fstr = luaL_checkstring(L, 1);
 	HashFunction::Function function;
 	if (!HashFunction::getConstant(fstr, function))
-		return luaL_error(L, "Invalid hash function: %s", fstr);
+		return luax_enumerror(L, "hash function", HashFunction::getConstants(function), fstr);
 
 	HashFunction::Value hashvalue;
 	if (lua_isstring(L, 2))