github.com/cockroachdb/tools@v0.0.0-20230222021103-a6d27438930d/go/buildutil/tags.go (about)

     1  // Copyright 2015 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  package buildutil
     6  
     7  // This logic was copied from stringsFlag from $GOROOT/src/cmd/go/build.go.
     8  
     9  import "fmt"
    10  
    11  const TagsFlagDoc = "a list of `build tags` to consider satisfied during the build. " +
    12  	"For more information about build tags, see the description of " +
    13  	"build constraints in the documentation for the go/build package"
    14  
    15  // TagsFlag is an implementation of the flag.Value and flag.Getter interfaces that parses
    16  // a flag value in the same manner as go build's -tags flag and
    17  // populates a []string slice.
    18  //
    19  // See $GOROOT/src/go/build/doc.go for description of build tags.
    20  // See $GOROOT/src/cmd/go/doc.go for description of 'go build -tags' flag.
    21  //
    22  // Example:
    23  //
    24  //	flag.Var((*buildutil.TagsFlag)(&build.Default.BuildTags), "tags", buildutil.TagsFlagDoc)
    25  type TagsFlag []string
    26  
    27  func (v *TagsFlag) Set(s string) error {
    28  	var err error
    29  	*v, err = splitQuotedFields(s)
    30  	if *v == nil {
    31  		*v = []string{}
    32  	}
    33  	return err
    34  }
    35  
    36  func (v *TagsFlag) Get() interface{} { return *v }
    37  
    38  func splitQuotedFields(s string) ([]string, error) {
    39  	// Split fields allowing '' or "" around elements.
    40  	// Quotes further inside the string do not count.
    41  	var f []string
    42  	for len(s) > 0 {
    43  		for len(s) > 0 && isSpaceByte(s[0]) {
    44  			s = s[1:]
    45  		}
    46  		if len(s) == 0 {
    47  			break
    48  		}
    49  		// Accepted quoted string. No unescaping inside.
    50  		if s[0] == '"' || s[0] == '\'' {
    51  			quote := s[0]
    52  			s = s[1:]
    53  			i := 0
    54  			for i < len(s) && s[i] != quote {
    55  				i++
    56  			}
    57  			if i >= len(s) {
    58  				return nil, fmt.Errorf("unterminated %c string", quote)
    59  			}
    60  			f = append(f, s[:i])
    61  			s = s[i+1:]
    62  			continue
    63  		}
    64  		i := 0
    65  		for i < len(s) && !isSpaceByte(s[i]) {
    66  			i++
    67  		}
    68  		f = append(f, s[:i])
    69  		s = s[i:]
    70  	}
    71  	return f, nil
    72  }
    73  
    74  func (v *TagsFlag) String() string {
    75  	return "<tagsFlag>"
    76  }
    77  
    78  func isSpaceByte(c byte) bool {
    79  	return c == ' ' || c == '\t' || c == '\n' || c == '\r'
    80  }