run_example_wasm.go

     1  // Copyright 2019 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  //go:build js || wasip1
     6  
     7  package testing
     8  
     9  import (
    10  	"fmt"
    11  	"io"
    12  	"os"
    13  	"strings"
    14  	"time"
    15  )
    16  
    17  // TODO(@musiol, @odeke-em): unify this code back into
    18  // example.go when js/wasm gets an os.Pipe implementation.
    19  func runExample(eg InternalExample) (ok bool) {
    20  	if chatty.on {
    21  		fmt.Printf("%s=== RUN   %s\n", chatty.prefix(), eg.Name)
    22  	}
    23  
    24  	// Capture stdout to temporary file. We're not using
    25  	// os.Pipe because it is not supported on js/wasm.
    26  	stdout := os.Stdout
    27  	f := createTempFile(eg.Name)
    28  	os.Stdout = f
    29  	finished := false
    30  	start := time.Now()
    31  
    32  	// Clean up in a deferred call so we can recover if the example panics.
    33  	defer func() {
    34  		timeSpent := time.Since(start)
    35  
    36  		// Restore stdout, get output and remove temporary file.
    37  		os.Stdout = stdout
    38  		var buf strings.Builder
    39  		_, seekErr := f.Seek(0, io.SeekStart)
    40  		_, readErr := io.Copy(&buf, f)
    41  		out := buf.String()
    42  		f.Close()
    43  		os.Remove(f.Name())
    44  		if seekErr != nil {
    45  			fmt.Fprintf(os.Stderr, "testing: seek temp file: %v\n", seekErr)
    46  			os.Exit(1)
    47  		}
    48  		if readErr != nil {
    49  			fmt.Fprintf(os.Stderr, "testing: read temp file: %v\n", readErr)
    50  			os.Exit(1)
    51  		}
    52  
    53  		err := recover()
    54  		ok = eg.processRunResult(out, timeSpent, finished, err)
    55  	}()
    56  
    57  	// Run example.
    58  	eg.F()
    59  	finished = true
    60  	return
    61  }
    62  
    63  func createTempFile(exampleName string) *os.File {
    64  	for i := 0; ; i++ {
    65  		name := fmt.Sprintf("%s/go-example-stdout-%s-%d.txt", os.TempDir(), exampleName, i)
    66  		f, err := os.OpenFile(name, os.O_RDWR|os.O_CREATE|os.O_EXCL, 0600)
    67  		if err != nil {
    68  			if os.IsExist(err) {
    69  				continue
    70  			}
    71  			fmt.Fprintf(os.Stderr, "testing: open temp file: %v\n", err)
    72  			os.Exit(1)
    73  		}
    74  		return f
    75  	}
    76  }
    77
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