ably-wasm-demo

Compiling ably-go to wasm

The target go code to be compiled to web assembly can be found in the /src folder.

Two files need from your Go installation are required, they can be found at $GOROOT/misc/wasm

• wasm_exec.html
• wasm_exec.js

After copying these files to this project in wasm_exec.html I renamed test.wasm to lib.wasm I also renamed the file itself from wasm_exec.html > index.html.

The Go code in /src is compiled into a Web Assembly file called lib.wasm. To compile to wasm, the GOARCH env var needs to be changed to wasm and the GOOS env var needs to be changed to js.

Can compile main.go to Web Assembly with this command which sets these go env vars. run this command from cd src && GOARCH=wasm GOOS=js go build -o lib.wasm main.go

After compiling main.go to lib.wasm, move the lib.wasm to the project root folder. Then start the local server with go run server.go. Then navigate to localhost:8080 A html page with a run button should be served. Clicking on the run button will execute the wasm file in the browser.

Observations

ably-go v1.2.7

This version of the ably-go SDK does compile to wasm. Was able to compile some Go code that attempts to publish to an Ably Realtime channel. An invalid key error was encountered when the Go code attempted to use a key stored in an env var. After hardcoding the key and attempting to execute the compiled wasm in a browser the following error was seen in every few seconds in the browser console..

2022/07/02 11:40:55 [ERROR] Received recoverable error websocket.Dial wss://realtime.ably.io:443?echo=true&format=msgpack&heartbeats=true&key=<redacted>&timestamp=1656758455288&v=1.2: dial tcp: lookup realtime.ably.io: Protocol not available

Tried setting a client option to use json protocol instead of message pack protocol. all that did was change the error message to

2022/07/02 11:49:00 [ERROR] Received recoverable error websocket.Dial wss://realtime.ably.io:443?echo=true&format=json&heartbeats=true&key=<redacted>&timestamp=1656758940832&v=1.2: dial tcp: lookup realtime.ably.io: Protocol not available

ably-go v1.2.8

In this newly released version of the SDK, the deprecated websocket package https://pkg.go.dev/golang.org/x/net/websocket was replaced with package https://pkg.go.dev/nhooyr.io/websocket I wanted to see if this changed allowed ably-go to compile to wasm and execute in a browser.

When attempting to compile the same Go code to wasm. The code failed to compile with this error.

C:\dev\go\pkg\mod\github.com\ably\ably-go@v1.2.8\ably\websocket.go:105:6: ops.HTTPHeader undefined (type websocket.DialOptions has no field or method HTTPHeader)
C:\dev\go\pkg\mod\github.com\ably\ably-go@v1.2.8\ably\websocket.go:106:6: ops.HTTPHeader undefined (type websocket.DialOptions has no field or method HTTPHeader)

Tried commenting out lines 105 and 105 of websocket.go to see if this changed anything. This allowed the go code to compile to wasm.

Ran the local server along side my ablyeye demo.

Was able to publish a realtime message from the browser to ablyeye.

I captured a gif of this running