Add JSON API (#729)

* Add JSON API

src/_manifest.lua

@@ -22,6 +22,8 @@
 		"base/moduledownloader.lua",
 		"base/semver.lua",
 		"base/http.lua",
+		"base/json.lua",
+		"base/jsonwrapper.lua",
 
 		-- configuration data
 		"base/field.lua",

src/base/jsonwrapper.lua

@@ -0,0 +1,46 @@
+--
+-- jsonwrapper.lua
+-- Provides JSON encoding and decoding API by wrapping a third-party JSON library
+-- Copyright (c) 2017 Jason Perkins and the Premake project
+--
+
+	json = {}
+
+	local implementation = dofile('json.lua')
+	local err
+
+	function implementation.assert(condition, message)
+		if not condition then
+			err = message
+		end
+
+		-- The JSON library we're using assumes that encode error handlers will
+		-- abort on error. It doesn't have the same assumption for decode error
+		-- handlers, but we're using this same function for both.
+
+		assert(condition, message)
+	end
+
+	function json.encode(value)
+		err = nil
+
+		local success, result = pcall(implementation.encode, implementation, value)
+
+		if not success then
+			return nil, err
+		end
+
+		return result
+	end
+
+	function json.decode(value)
+		err = nil
+
+		local success, result = pcall(implementation.decode, implementation, value)
+
+		if not success then
+			return nil, err
+		end
+
+		return result
+	end

tests/_tests.lua

@@ -18,6 +18,7 @@ return {
 	"base/test_uuid.lua",
 	"base/test_versions.lua",
 	"base/test_http.lua",
+	"base/test_json.lua",
 
 	-- Workspace object tests
 	"workspace/test_eachconfig.lua",

tests/base/test_json.lua

@@ -0,0 +1,32 @@
+--
+-- tests/base/test_json.lua
+-- Tests the json API
+-- Copyright (c) 2017 Jason Perkins and the Premake project
+--
+
+	local p = premake
+
+	local suite = test.declare("premake_json")
+
+	function suite.json_encode()
+		local result = json.encode({foo = "bar"})
+		result = result:gsub('%s*', ''),
+		test.isequal(result, '{"foo":"bar"}')
+	end
+
+	function suite.json_decode()
+		local result = json.decode('{ "foo": "bar" }')
+		test.isequal(result, { foo = "bar" })
+	end
+
+	function suite.json_encode_error()
+		local result, err = json.encode({ fubar = function() end })
+		test.isnil(result)
+		test.isequal(type(err), "string")
+	end
+
+	function suite.json_decode_error()
+		local result, err = json.decode("fubar string")
+		test.isnil(result)
+		test.isequal(type(err), "string")
+	end