Grpc-Message header is not percent decoded

[evanj]

The gRPC specification states "Status-Message is [...] physically encoded as UTF-8 followed by percent-encoding." However, the gRPC-Web client does not percent decode the error detail. The official NodeJS gRPC client does.

Example response payload:

HTTP/1.0 200 OK
Content-Type: application/grpc-web-text
Content-Length: 0
Grpc-Status: 11
Grpc-Message: emoji error: %F0%9F%98%80

The gRPC-Web client decodes this into an error object with details of 'emoji error: %F0%9F%98%80'. The NodeJS client decodes it into 'emoji error: \u{0001F600}' ('emoji error: 😀')

A brief inspection of the code seems to suggest this needs to be done if the header comes from either the trailers or the XHR response:

grpc-web/javascript/net/grpc/web/grpcwebclientreadablestream.js

Line 201 in def314a

message: self.xhr_.getResponseHeader(GRPC_STATUS_MESSAGE)

[stanley-cheung]

This should be fixed by #858 in release 1.2.0. Added some decodeURIComponent call in the relevant places.