add Promise.json helper

http.lua

@@ -47,3 +47,7 @@ function Promise.http(http, url, opts)
         end)
     end)
 end
+
+function Promise.json(http, url, opts)
+    return Promise.http(http, url, opts):next(function(res) return res.json() end)
+end

http.spec.lua

@@ -20,6 +20,13 @@ mtt.register("Promise.http GET with async/await", function()
     end)
 end)
 
+mtt.register("Promise.json GET with async/await", function()
+    return Promise.async(function(await)
+        local joke = await(Promise.json(http, "https://api.chucknorris.io/jokes/random"))
+        assert(type(joke.value) == "string")
+    end)
+end)
+
 mtt.register("Promise.http/all GET", function(callback)
     local p1 = Promise.http(http, "https://api.chucknorris.io/jokes/random"):next(toJson)
     local p2 = Promise.http(http, "https://api.chucknorris.io/jokes/random"):next(toJson)

readme.md

@@ -226,6 +226,18 @@ end):catch(function(res)
 end)
 ```
 
+## `Promise.json(http, url, opts?)`
+
+Helper function for `Promise.http` that parses a json response
+
+Example:
+```lua
+-- call chuck norris api: https://api.chucknorris.io/ and expect json-response
+Promise.json(http, "https://api.chucknorris.io/jokes/random"):next(function(joke)
+    assert(type(joke.value) == "string")
+end)
+```
+
 ## `Promise.mods_loaded()`
 
 Resolved on mods loaded (`minetest.register_on_mods_loaded`)