discovery.go

Documentation: golang.org/x/tools/go/vcs

     1  // Copyright 2012 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 vcs
     6  
     7  import (
     8  	"encoding/xml"
     9  	"fmt"
    10  	"io"
    11  	"strings"
    12  )
    13  
    14  // charsetReader returns a reader for the given charset. Currently
    15  // it only supports UTF-8 and ASCII. Otherwise, it returns a meaningful
    16  // error which is printed by go get, so the user can find why the package
    17  // wasn't downloaded if the encoding is not supported. Note that, in
    18  // order to reduce potential errors, ASCII is treated as UTF-8 (i.e. characters
    19  // greater than 0x7f are not rejected).
    20  func charsetReader(charset string, input io.Reader) (io.Reader, error) {
    21  	switch strings.ToLower(charset) {
    22  	case "ascii":
    23  		return input, nil
    24  	default:
    25  		return nil, fmt.Errorf("can't decode XML document using charset %q", charset)
    26  	}
    27  }
    28  
    29  // parseMetaGoImports returns meta imports from the HTML in r.
    30  // Parsing ends at the end of the <head> section or the beginning of the <body>.
    31  //
    32  // This copy of cmd/go/internal/vcs.parseMetaGoImports always operates
    33  // in IgnoreMod ModuleMode.
    34  func parseMetaGoImports(r io.Reader) (imports []metaImport, err error) {
    35  	d := xml.NewDecoder(r)
    36  	d.CharsetReader = charsetReader
    37  	d.Strict = false
    38  	var t xml.Token
    39  	for {
    40  		t, err = d.RawToken()
    41  		if err != nil {
    42  			if err == io.EOF || len(imports) > 0 {
    43  				err = nil
    44  			}
    45  			return
    46  		}
    47  		if e, ok := t.(xml.StartElement); ok && strings.EqualFold(e.Name.Local, "body") {
    48  			return
    49  		}
    50  		if e, ok := t.(xml.EndElement); ok && strings.EqualFold(e.Name.Local, "head") {
    51  			return
    52  		}
    53  		e, ok := t.(xml.StartElement)
    54  		if !ok || !strings.EqualFold(e.Name.Local, "meta") {
    55  			continue
    56  		}
    57  		if attrValue(e.Attr, "name") != "go-import" {
    58  			continue
    59  		}
    60  		if f := strings.Fields(attrValue(e.Attr, "content")); len(f) == 3 {
    61  			// Ignore VCS type "mod", which is applicable only in module mode.
    62  			if f[1] == "mod" {
    63  				continue
    64  			}
    65  			imports = append(imports, metaImport{
    66  				Prefix:   f[0],
    67  				VCS:      f[1],
    68  				RepoRoot: f[2],
    69  			})
    70  		}
    71  	}
    72  }
    73  
    74  // attrValue returns the attribute value for the case-insensitive key
    75  // `name', or the empty string if nothing is found.
    76  func attrValue(attrs []xml.Attr, name string) string {
    77  	for _, a := range attrs {
    78  		if strings.EqualFold(a.Name.Local, name) {
    79  			return a.Value
    80  		}
    81  	}
    82  	return ""
    83  }
    84
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