• Tilman Dilo's avatar
    cmd/vet: fix panic and handling of XML in struct field tag check · 1657d76d
    Tilman Dilo authored
    The check for duplicate struct field tags introduced in CL 16704
    triggers a panic when an anonymous struct field with a duplicate name
    is encountered. For such a field, the names slice of the ast.Field is
    nil but accessed regardless to generate the warning message.
    
    Additionally, the check produces false positives for XML tags in some
    cases:
    
    - When fields are encoded as XML attributes, a warning is produced when
      an attribute reuses a name previously used for an element.
    
      Example:
        type Foo struct {
            First int `xml:"a"`
            NoDup int `xml:"a,attr"` // warning about reuse of "a"
        }
    
    - When XMLName is used to set the name of the enclosing struct element,
      it is treated as a regular struct field.
    
      Example:
        type Bar struct {
            XMLName xml.Name `xml:"a"`
            NoDup   int      `xml:"a"` // warning about reuse of "a"
        }
    
    This commit addresses all three issues. The panic is avoided by using
    the type name instead of the field name for anonymous struct fields when
    generating the warning message. An additional namespace for checking XML
    attribute names separately from element names is introduced. Lastly,
    fields named XMLName are excluded from the check for duplicate tags.
    
    Updates #18256
    
    Change-Id: Ida48ea8584b56bd4d12ae3ebd588a66ced2594cc
    Reviewed-on: https://go-review.googlesource.com/34070
    Run-TryBot: Rob Pike <r@golang.org>
    TryBot-Result: Gobot Gobot <gobot@golang.org>
    Reviewed-by: 's avatarRob Pike <r@golang.org>
    1657d76d
structtag.go 4.95 KB