better error-handling and memoize fetch

Author: konsumer

sqldef-wasm.go

@@ -1,8 +1,8 @@
+// +build js
 // This is a light wasm wraper around just the DDL conversion stuff
 package main
 
 import (
-	"log"
 	"strings"
 	"syscall/js"
 	"github.com/k0kubun/sqldef/schema"
@@ -19,14 +19,15 @@ func diff(this js.Value, args []js.Value) interface {} {
 	}
 	ddls, err := schema.GenerateIdempotentDDLs(generatorMode, desiredDDLs, currentDDLs)
 	out := strings.Join(ddls, ";\n")
-	callback.Invoke(js.Null(), out)
 
 	// TODO: Need to figure out how to pass error in callback
 	if err != nil {
-		log.Fatal(err)
+		callback.Invoke(err.Error(), out)
+		return false
+	} else {
+		callback.Invoke(js.Null(), out)
+		return true
 	}
-	_ = err
-	return true
 }
 
 func main() {

sqldef.wasm

@@ -1,14 +1,11 @@
+let source
+
 /* global WebAssembly, fetch, Go,_SQLDEF */
 window.sqldef = async (dbType, desiredDDLs, currentDDLs) => {
   if (WebAssembly) {
-    if (WebAssembly && !WebAssembly.instantiateStreaming) { // polyfill
-      WebAssembly.instantiateStreaming = async (resp, importObject) => {
-        const source = await (await resp).arrayBuffer()
-        return WebAssembly.instantiate(source, importObject)
-      }
-    }
+    source = source || (await (await fetch('sqldef.wasm')).arrayBuffer())
     const go = new Go()
-    const result = await WebAssembly.instantiateStreaming(fetch('sqldef.wasm'), go.importObject)
+    const result = await WebAssembly.instantiate(source, go.importObject)
     go.run(result.instance)
     return new Promise((resolve, reject) => {
       _SQLDEF(dbType, desiredDDLs, currentDDLs, (err, ret) => {