Set Accept-Encoding to identity by default

Fixes #370

Author: timhall

specs/Specs_WebRequest.bas

@@ -191,6 +191,22 @@ Public Function Specs() As SpecSuite
         .Expect(Request.Accept).ToEqual "x-custom/text"
     End With
 
+    ' AcceptEncoding
+    ' --------------------------------------------- '
+    With Specs.It("AcceptEncoding should be set to identity by default")
+        Set Request = New WebRequest
+        
+        .Expect(Request.AcceptEncoding).ToEqual "identity"
+    End With
+    
+    With Specs.It("AcceptEncoding should allow override")
+        Set Request = New WebRequest
+        
+        Request.AcceptEncoding = "gzip"
+        
+        .Expect(Request.AcceptEncoding).ToEqual "gzip"
+    End With
+    
     ' ContentLength
     ' --------------------------------------------- '
     With Specs.It("ContentLength should be set from length of Body")
@@ -502,15 +518,17 @@ Public Function Specs() As SpecSuite
         Request.Method = WebMethod.HttpPost
         Request.ContentType = "text/plain"
         Request.Accept = "text/csv"
+        Request.AcceptEncoding = "gzip"
         Request.ContentLength = 100
 
         .Expect(Request.Headers.Count).ToEqual 0
 
         Request.Prepare
 
-        .Expect(Request.Headers.Count).ToBeGTE 3
+        .Expect(Request.Headers.Count).ToBeGTE 4
         .Expect(WebHelpers.FindInKeyValues(Request.Headers, "Content-Type")).ToEqual "text/plain"
         .Expect(WebHelpers.FindInKeyValues(Request.Headers, "Accept")).ToEqual "text/csv"
+        .Expect(WebHelpers.FindInKeyValues(Request.Headers, "Accept-Encoding")).ToEqual "gzip"
         .Expect(WebHelpers.FindInKeyValues(Request.Headers, "Content-Length")).ToEqual "100"
     End With
 
@@ -538,12 +556,12 @@ Public Function Specs() As SpecSuite
 
         Request.Prepare
 
-        .Expect(Request.Headers.Count).ToEqual 2
+        .Expect(Request.Headers.Count).ToEqual 3
 
         Request.Body = "non-empty"
         Request.Prepare
 
-        .Expect(Request.Headers.Count).ToEqual 4
+        .Expect(Request.Headers.Count).ToEqual 5
 
         .Expect(WebHelpers.FindInKeyValues(Request.Headers, "Content-Type")).ToEqual "text/plain"
         .Expect(WebHelpers.FindInKeyValues(Request.Headers, "Content-Length")).ToEqual "9"

src/WebClient.cls

@@ -642,6 +642,11 @@ Public Function PrepareCurlRequest(Request As WebRequest) As String
     If Me.FollowRedirects Then
         web_Curl = web_Curl & " --location"
     End If
+    
+    ' Enable compressed if Accept-Encoding != "identity"
+    If Request.AcceptEncoding <> "identity" Then
+        web_Curl = web_Curl & " --compressed"
+    End If
 
     ' Set headers and cookies
     For Each web_KeyValue In Request.Headers

src/WebRequest.cls

@@ -59,6 +59,7 @@ Private web_pBody As Variant
 Private web_pConvertedBody As Variant
 Private web_pContentType As String
 Private web_pAccept As String
+Private web_pAcceptEncoding As String
 Private web_pContentLength As Long
 Private web_pId As String
 
@@ -413,6 +414,26 @@ Public Property Let Accept(Value As String)
     web_pAccept = Value
 End Property
 
+''
+' WinHTTP does not support decompression at this time (Jan. 2019).
+' If not Accept-Encoding is passed to the server, [RFC 7231](https://tools.ietf.org/html/rfc7231#section-5.3.4)
+' states that "any content-coding is considered acceptable by the user agent"
+' -> Explicitly set Accept-Encoding
+'
+' cURL supports --compressed, which automatically decompresses gzip and other compressed responses
+' -> If AcceptEncoding != "identity", enable --compressed flag
+''
+Public Property Get AcceptEncoding() As String
+    If web_pAcceptEncoding <> "" Then
+        AcceptEncoding = web_pAcceptEncoding
+    Else
+        AcceptEncoding = "identity"
+    End If
+End Property
+Public Property Let AcceptEncoding(Value As String)
+    web_pAcceptEncoding = Value
+End Property
+
 ''
 ' Set automatically by length of `Body`,
 ' but can be overriden to set `Content-Length` header for request.
@@ -741,6 +762,7 @@ Public Sub Prepare()
     ' Add/replace general headers for request
     SetHeader "User-Agent", Me.UserAgent
     SetHeader "Accept", Me.Accept
+    SetHeader "Accept-Encoding", Me.AcceptEncoding
     If Me.Method <> WebMethod.HttpGet Or Me.ContentLength > 0 Then
         SetHeader "Content-Type", Me.ContentType
         SetHeader "Content-Length", VBA.CStr(Me.ContentLength)