From 6d3884b0ceba66173ae068e4d44c593e9e34856e Mon Sep 17 00:00:00 2001
From: "Gerasimos (Makis) Maropoulos" <kataras2006@hotmail.com>
Date: Wed, 16 Jun 2021 13:52:39 +0300
Subject: [PATCH] add iris.IsErrEmptyJSON helper. See HISTORY.md

---
 HISTORY.md                                    | 19 +++++++++++++++++
 .../basic/middleware/main.go                  |  6 ++++++
 aliases.go                                    |  4 ++++
 context/context.go                            | 21 +++++++++++++++++--
 4 files changed, 48 insertions(+), 2 deletions(-)

diff --git a/HISTORY.md b/HISTORY.md
index 6b9230e0..077d2058 100644
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -28,6 +28,25 @@ The codebase for Dependency Injection, Internationalization and localization and
 
 ## Fixes and Improvements
 
+- New `iris.IsErrEmptyJSON(err) bool` which reports whether the given "err" is caused by a
+`Context.ReadJSON` call when the request body didn't start with { (or it was totally empty). 
+
+Example Code:
+
+```go
+func handler(ctx iris.Context) {
+    var opts SearchOptions
+    if err := ctx.ReadJSON(&opts); err != nil && !iris.IsErrEmptyJSON(err) {
+        ctx.StopWithJSON(iris.StatusBadRequest, iris.Map{"message": "unable to parse body"})
+        return
+    }
+
+    // [...continue with default values of "opts" struct if the client didn't provide some]
+}
+```
+
+That means that the client can optionally set a JSON body.
+	
 - New `APIContainer.EnableStrictMode(bool)` to disable automatic payload binding and panic on missing dependencies for exported struct'sfields or function's input parameters on MVC controller or hero function or PartyConfigurator.
 
 - New `Party.PartyConfigure(relativePath string, partyReg ...PartyConfigurator) Party` helper, registers a children Party like `Party` and `PartyFunc` but instead it accepts a structure value which may contain one or more of the dependencies registered by `RegisterDependency` or `ConfigureContainer().RegisterDependency` methods and fills the unset/zero exported struct's fields respectfully (useful when the api's dependencies amount are too much to pass on a function).
diff --git a/_examples/dependency-injection/basic/middleware/main.go b/_examples/dependency-injection/basic/middleware/main.go
index 6faf607d..137b3d61 100644
--- a/_examples/dependency-injection/basic/middleware/main.go
+++ b/_examples/dependency-injection/basic/middleware/main.go
@@ -47,6 +47,12 @@ func newApp() *iris.Application {
 	// or 202 status code and empty body
 	// or a 409 status code and "my_error" body.
 	app.ConfigureContainer(func(api *iris.APIContainer) {
+		// TODO: fix that test as well.
+		// api.Self.SetExecutionRules(iris.ExecutionRules{
+		// 	Begin: iris.ExecutionOptions{
+		// 		Force: true,
+		// 	},
+		// })
 		api.Use(middleware)
 		api.Post("/{id:int}", handler)
 	})
diff --git a/aliases.go b/aliases.go
index a70c7ef8..cc037359 100644
--- a/aliases.go
+++ b/aliases.go
@@ -496,6 +496,10 @@ var (
 	// A shortcut for the `context#CookieEncoding`.
 	CookieEncoding = context.CookieEncoding
 
+	// IsErrEmptyJSON reports whether the given "err" is caused by a
+	// Context.ReadJSON call when the request body
+	// didn't start with { or it was totally empty.
+	IsErrEmptyJSON = context.IsErrEmptyJSON
 	// IsErrPath can be used at `context#ReadForm` and `context#ReadQuery`.
 	// It reports whether the incoming error is type of `schema.ErrPath`,
 	// which can be ignored when server allows unknown post values to be sent by the client.
diff --git a/context/context.go b/context/context.go
index 600c3227..96414fb9 100644
--- a/context/context.go
+++ b/context/context.go
@@ -2311,13 +2311,13 @@ func (ctx *Context) decodeBody(outPtr interface{}, decoder internalBodyDecoder)
 	// but this is up to the user's custom Decode implementation*
 	//
 	// See 'BodyDecoder' for more.
-	if decoder, isDecoder := outPtr.(BodyDecoder); isDecoder {
+	if structDecoder, isDecoder := outPtr.(BodyDecoder); isDecoder {
 		rawData, err := ctx.GetBody()
 		if err != nil {
 			return err
 		}
 
-		return decoder.Decode(rawData)
+		return structDecoder.Decode(rawData)
 	}
 
 	err := decoder.Decode(outPtr)
@@ -2465,6 +2465,23 @@ func (ctx *Context) ReadYAML(outPtr interface{}) error {
 }
 
 var (
+	// IsErrEmptyJSON reports whether the given "err" is caused by a
+	// Context.ReadJSON call when the request body
+	// didn't start with { or it was totally empty.
+	IsErrEmptyJSON = func(err error) bool {
+		if err == nil {
+			return false
+		}
+
+		if v, ok := err.(*json.SyntaxError); ok {
+			// standard go json encoder error.
+			return v.Offset == 0 && v.Error() == "unexpected end of JSON input"
+		}
+
+		// when optimization is enabled, the jsoniter will report the following error:
+		return strings.Contains(err.Error(), "readObjectStart: expect {")
+	}
+
 	// IsErrPath can be used at `context#ReadForm` and `context#ReadQuery`.
 	// It reports whether the incoming error
 	// can be ignored when server allows unknown post values to be sent by the client.