main.go

Documentation: github.com/shurcooL/vfsgen/cmd/vfsgendev

     1  // vfsgendev is a convenience tool for using vfsgen in a common development configuration.
     2  package main
     3  
     4  import (
     5  	"bytes"
     6  	"flag"
     7  	"fmt"
     8  	"go/build"
     9  	"io"
    10  	"log"
    11  	"os"
    12  	"os/exec"
    13  	"path/filepath"
    14  )
    15  
    16  var (
    17  	sourceFlag = flag.String("source", "", "Specifies the http.FileSystem variable to use as source.")
    18  	tagFlag    = flag.String("tag", "dev", "Specifies a single build tag to use for source. The output will include a negated version.")
    19  	nFlag      = flag.Bool("n", false, "Print the generated source but do not run it.")
    20  )
    21  
    22  func usage() {
    23  	fmt.Fprintln(os.Stderr, `Usage: vfsgendev [flags] -source="import/path".VariableName`)
    24  	flag.PrintDefaults()
    25  }
    26  
    27  func main() {
    28  	flag.Usage = usage
    29  	flag.Parse()
    30  	if flag.NArg() != 0 {
    31  		flag.Usage()
    32  		os.Exit(2)
    33  	}
    34  	importPath, variableName, err := parseSourceFlag(*sourceFlag)
    35  	if err != nil {
    36  		fmt.Fprintln(os.Stderr, "-source flag has invalid value:", err)
    37  		fmt.Fprintln(os.Stderr)
    38  		flag.Usage()
    39  		os.Exit(2)
    40  	}
    41  	tag, err := parseTagFlag(*tagFlag)
    42  	if err != nil {
    43  		fmt.Fprintln(os.Stderr, "-tag flag has invalid value:", err)
    44  		fmt.Fprintln(os.Stderr)
    45  		flag.Usage()
    46  		os.Exit(2)
    47  	}
    48  
    49  	err = run(importPath, variableName, tag)
    50  	if err != nil {
    51  		log.Fatalln(err)
    52  	}
    53  }
    54  
    55  func run(importPath, variableName, tag string) error {
    56  	bctx := build.Default
    57  	bctx.BuildTags = []string{tag}
    58  	packageName, variableComment, err := lookupNameAndComment(bctx, importPath, variableName)
    59  	if err != nil {
    60  		return err
    61  	}
    62  
    63  	var buf bytes.Buffer
    64  	err = generateTemplate.Execute(&buf, data{
    65  		ImportPath:      importPath,
    66  		PackageName:     packageName,
    67  		BuildTags:       "!" + tag,
    68  		VariableName:    variableName,
    69  		VariableComment: variableComment,
    70  	})
    71  	if err != nil {
    72  		return err
    73  	}
    74  
    75  	if *nFlag {
    76  		io.Copy(os.Stdout, &buf)
    77  		return nil
    78  	}
    79  
    80  	err = goRun(buf.String(), tag)
    81  	return err
    82  }
    83  
    84  // goRun runs Go code src with build tags.
    85  func goRun(src string, tags string) error {
    86  	// Create a temp folder.
    87  	tempDir, err := os.MkdirTemp("", "vfsgendev_")
    88  	if err != nil {
    89  		return err
    90  	}
    91  	defer func() {
    92  		err := os.RemoveAll(tempDir)
    93  		if err != nil {
    94  			fmt.Fprintln(os.Stderr, "warning: error removing temp dir:", err)
    95  		}
    96  	}()
    97  
    98  	// Write the source code file.
    99  	tempFile := filepath.Join(tempDir, "generate.go")
   100  	err = os.WriteFile(tempFile, []byte(src), 0600)
   101  	if err != nil {
   102  		return err
   103  	}
   104  
   105  	// Compile and run the program.
   106  	cmd := exec.Command("go", "run", "-tags="+tags, tempFile)
   107  	cmd.Stdout = os.Stdout
   108  	cmd.Stderr = os.Stderr
   109  	return cmd.Run()
   110  }
   111
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