Add test coverage support (#41)

* Move index.html to separate file with Go 1.16 embedded files * Add test coverage support Overrides three file system operations for the purposes of reading and writing the coverage profile file. The contents are copied out of the JS runtime and written again to the real file. * Extract FS wrappers to 'overrideFS' function Also guard use of global TextDecoder if not supported. * Wrap each FS operation, switch from writeSync() to write(), and bind "fs" as "this"
agnivade · Dec 20, 2022 · bba38b6 · bba38b6
1 parent 8753b3a
commit bba38b6
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Showing 4 changed files with 139 additions and 77 deletions.
diff --git a/go.mod b/go.mod
@@ -1,6 +1,6 @@
 module github.com/agnivade/wasmbrowsertest
 
-go 1.12
+go 1.16
 
 require (
 	github.com/chromedp/cdproto v0.0.0-20221108233440-fad8339618ab

diff --git a/handler.go b/handler.go
@@ -1,6 +1,7 @@
 package main
 
 import (
+	_ "embed"
 	"html/template"
 	"io/ioutil"
 	"log"
@@ -14,22 +15,27 @@ import (
 	"time"
 )
 
+//go:embed index.html
+var indexHTML string
+
 type wasmServer struct {
-	indexTmpl  *template.Template
-	wasmFile   string
-	wasmExecJS []byte
-	args       []string
-	envMap     map[string]string
-	logger     *log.Logger
+	indexTmpl    *template.Template
+	wasmFile     string
+	wasmExecJS   []byte
+	args         []string
+	coverageFile string
+	envMap       map[string]string
+	logger       *log.Logger
 }
 
-func NewWASMServer(wasmFile string, args []string, l *log.Logger) (http.Handler, error) {
+func NewWASMServer(wasmFile string, args []string, coverageFile string, l *log.Logger) (http.Handler, error) {
 	var err error
 	srv := &wasmServer{
-		wasmFile: wasmFile,
-		args:     args,
-		logger:   l,
-		envMap:   make(map[string]string),
+		wasmFile:     wasmFile,
+		args:         args,
+		coverageFile: coverageFile,
+		logger:       l,
+		envMap:       make(map[string]string),
 	}
 
 	for _, env := range os.Environ() {
@@ -56,13 +62,15 @@ func (ws *wasmServer) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	case "/", "/index.html":
 		w.Header().Set("Content-Type", "text/html; charset=UTF-8")
 		data := struct {
-			WASMFile string
-			Args     []string
-			EnvMap   map[string]string
+			WASMFile     string
+			Args         []string
+			CoverageFile string
+			EnvMap       map[string]string
 		}{
-			WASMFile: filepath.Base(ws.wasmFile),
-			Args:     ws.args,
-			EnvMap:   ws.envMap,
+			WASMFile:     filepath.Base(ws.wasmFile),
+			Args:         ws.args,
+			CoverageFile: ws.coverageFile,
+			EnvMap:       ws.envMap,
 		}
 		err := ws.indexTmpl.Execute(w, data)
 		if err != nil {
@@ -89,60 +97,3 @@ func (ws *wasmServer) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		}
 	}
 }
-
-const indexHTML = `<!doctype html>
-<!--
-Copyright 2018 The Go Authors. All rights reserved.
-Use of this source code is governed by a BSD-style
-license that can be found in the LICENSE file.
--->
-<html>
-
-<head>
-	<meta charset="utf-8">
-	<title>Go wasm</title>
-</head>
-
-<body>
-	<!--
-	Add the following polyfill for Microsoft Edge 17/18 support:
-	<script src="https://cdn.jsdelivr.net/npm/[email protected]/lib/encoding.min.js"></script>
-	(see https://caniuse.com/#feat=textencoder)
-	-->
-	<script src="wasm_exec.js"></script>
-	<script>
-		if (!WebAssembly.instantiateStreaming) { // polyfill
-			WebAssembly.instantiateStreaming = async (resp, importObject) => {
-				const source = await (await resp).arrayBuffer();
-				return await WebAssembly.instantiate(source, importObject);
-			};
-		}
-
-		let exitCode = 0;
-		function goExit(code) {
-			exitCode = code;
-		}
-
-		(async() => {
-			const go = new Go();
-			go.argv = [{{range $i, $item := .Args}} {{if $i}}, {{end}} "{{$item}}" {{end}}];
-			// The notFirst variable sets itself to true after first iteration. This is to put commas in between.
-			go.env = { {{ $notFirst := false }}
-			{{range $key, $val := .EnvMap}} {{if $notFirst}}, {{end}} {{$key}}: "{{$val}}" {{ $notFirst = true }}
-			{{end}} };
-			go.exit = goExit;
-			let mod, inst;
-			await WebAssembly.instantiateStreaming(fetch("{{.WASMFile}}"), go.importObject).then((result) => {
-				mod = result.module;
-				inst = result.instance;
-			}).catch((err) => {
-				console.error(err);
-			});
-			await go.run(inst);
-			document.getElementById("doneButton").disabled = false;
-		})();
-	</script>
-
-	<button id="doneButton" style="display: none;" disabled>Done</button>
-</body>
-</html>`
diff --git a/index.html b/index.html
@@ -0,0 +1,99 @@
+<!doctype html>
+<!--
+Copyright 2018 The Go Authors. All rights reserved.
+Use of this source code is governed by a BSD-style
+license that can be found in the LICENSE file.
+-->
+<html>
+
+<head>
+	<meta charset="utf-8">
+	<title>Go wasm</title>
+</head>
+
+<body>
+	<!--
+	Add the following polyfill for Microsoft Edge 17/18 support:
+	<script src="https://cdn.jsdelivr.net/npm/[email protected]/lib/encoding.min.js"></script>
+	(see https://caniuse.com/#feat=textencoder)
+	-->
+	<script src="wasm_exec.js"></script>
+	<script>
+		if (!WebAssembly.instantiateStreaming) { // polyfill
+			WebAssembly.instantiateStreaming = async (resp, importObject) => {
+				const source = await (await resp).arrayBuffer();
+				return await WebAssembly.instantiate(source, importObject);
+			};
+		}
+
+		let exitCode = 0;
+		function goExit(code) {
+			exitCode = code;
+		}
+		function enosys() {
+			const err = new Error("not implemented");
+			err.code = "ENOSYS";
+			return err;
+		}
+		let coverageProfileContents = "";
+		function overrideFS(fs) {
+			// A typical runtime opens fd's in sequence above the standard descriptors (0-2).
+			// Choose an arbitrarily high fd for the custom coverage file to avoid conflict with the actual runtime fd's.
+			const coverFileDescriptor = Number.MAX_SAFE_INTEGER; 
+			const coverFilePath = {{.CoverageFile}};
+			// Wraps the default operations with bind() to ensure internal usage of 'this' continues to work.
+			const defaultOpen = fs.open.bind(fs);
+			fs.open = (path, flags, mode, callback) => {
+				if (path === coverFilePath) {
+					callback(null, coverFileDescriptor);
+					return;
+				}
+				defaultOpen(path, flags, mode, callback);
+			};
+			const defaultClose = fs.close.bind(fs);
+			fs.close = (fd, callback) => {
+				if (fd === coverFileDescriptor) {
+					callback(null);
+					return;
+				}
+				defaultClose(fd, callback);
+			};
+			if (!globalThis.TextDecoder) {
+				throw new Error("globalThis.TextDecoder is not available, polyfill required");
+			}
+			const decoder = new TextDecoder("utf-8");
+			const defaultWrite = fs.write.bind(fs);
+			fs.write = (fd, buf, offset, length, position, callback) => {
+				if (fd === coverFileDescriptor) {
+					coverageProfileContents += decoder.decode(buf);
+					callback(null, buf.length);
+					return;
+				}
+				defaultWrite(fd, buf, offset, length, position, callback);
+			};
+		}
+
+		(async() => {
+			const go = new Go();
+			overrideFS(globalThis.fs)
+			go.argv = [{{range $i, $item := .Args}} {{if $i}}, {{end}} "{{$item}}" {{end}}];
+			// The notFirst variable sets itself to true after first iteration. This is to put commas in between.
+			go.env = { {{ $notFirst := false }}
+			{{range $key, $val := .EnvMap}} {{if $notFirst}}, {{end}} {{$key}}: "{{$val}}" {{ $notFirst = true }}
+			{{end}} };
+			go.exit = goExit;
+			let mod, inst;
+			await WebAssembly.instantiateStreaming(fetch("{{.WASMFile}}"), go.importObject).then((result) => {
+				mod = result.module;
+				inst = result.instance;
+			}).catch((err) => {
+				console.error(err);
+			});
+			await go.run(inst);
+			document.getElementById("doneButton").disabled = false;
+		})();
+	</script>
+
+	<button id="doneButton" style="display: none;" disabled>Done</button>
+</body>
+</html>
diff --git a/main.go b/main.go
@@ -25,7 +25,8 @@ import (
 )
 
 var (
-	cpuProfile *string
+	cpuProfile      *string
+	coverageProfile *string
 )
 
 func main() {
@@ -45,6 +46,7 @@ func main() {
 	}
 
 	cpuProfile = flag.String("test.cpuprofile", "", "")
+	coverageProfile = flag.String("test.coverprofile", "", "")
 
 	wasmFile := os.Args[1]
 	ext := path.Ext(wasmFile)
@@ -61,6 +63,9 @@ func main() {
 
 	passon := gentleParse(flag.CommandLine, os.Args[2:])
 	passon = append([]string{wasmFile}, passon...)
+	if *coverageProfile != "" {
+		passon = append(passon, "-test.coverprofile="+*coverageProfile)
+	}
 
 	// Need to generate a random port every time for tests in parallel to run.
 	l, err := net.Listen("tcp", "localhost:")
@@ -77,7 +82,7 @@ func main() {
 	}
 
 	// Setup web server.
-	handler, err := NewWASMServer(wasmFile, passon, logger)
+	handler, err := NewWASMServer(wasmFile, passon, *coverageProfile, logger)
 	if err != nil {
 		logger.Fatal(err)
 	}
@@ -117,10 +122,12 @@ func main() {
 		}
 		done <- struct{}{}
 	}()
+	var coverageProfileContents string
 	tasks := []chromedp.Action{
 		chromedp.Navigate(`http://localhost:` + port),
 		chromedp.WaitEnabled(`#doneButton`),
 		chromedp.Evaluate(`exitCode;`, &exitCode),
+		chromedp.Evaluate(`coverageProfileContents;`, &coverageProfileContents),
 	}
 	if *cpuProfile != "" {
 		// Prepend and append profiling tasks
@@ -152,6 +159,11 @@ func main() {
 			return WriteProfile(profile, outF, funcMap)
 		}))
 	}
+	if *coverageProfile != "" {
+		tasks = append(tasks, chromedp.ActionFunc(func(ctx context.Context) error {
+			return os.WriteFile(*coverageProfile, []byte(coverageProfileContents), 0644)
+		}))
+	}
 
 	err = chromedp.Run(ctx, tasks...)
 	if err != nil {