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Add Path.Index helper method #56

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merged 1 commit into from
Dec 2, 2017
Merged

Add Path.Index helper method #56

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11 changes: 4 additions & 7 deletions cmp/cmpopts/ignore.go
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Original file line number Diff line number Diff line change
Expand Up @@ -50,7 +50,7 @@ func (tf typeFilter) filter(p cmp.Path) bool {
if len(p) < 1 {
return false
}
t := p[len(p)-1].Type()
t := p.Last().Type()
for _, ti := range tf {
if t.AssignableTo(ti) {
return true
Expand Down Expand Up @@ -95,7 +95,7 @@ func (tf ifaceFilter) filter(p cmp.Path) bool {
if len(p) < 1 {
return false
}
t := p[len(p)-1].Type()
t := p.Last().Type()
for _, ti := range tf {
if t.AssignableTo(ti) {
return true
Expand Down Expand Up @@ -131,14 +131,11 @@ func newUnexportedFilter(typs ...interface{}) unexportedFilter {
return ux
}
func (xf unexportedFilter) filter(p cmp.Path) bool {
if len(p) < 2 {
return false
}
sf, ok := p[len(p)-1].(cmp.StructField)
sf, ok := p.Index(-1).(cmp.StructField)
if !ok {
return false
}
return xf.m[p[len(p)-2].Type()] && !isExported(sf.Name())
return xf.m[p.Index(-2).Type()] && !isExported(sf.Name())
}

// isExported reports whether the identifier is exported.
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17 changes: 14 additions & 3 deletions cmp/path.go
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Original file line number Diff line number Diff line change
Expand Up @@ -94,10 +94,21 @@ func (pa *Path) pop() {
// Last returns the last PathStep in the Path.
// If the path is empty, this returns a non-nil PathStep that reports a nil Type.
func (pa Path) Last() PathStep {
if len(pa) > 0 {
return pa[len(pa)-1]
return pa.Index(-1)
}

// Index returns the ith step in the Path and supports negative indexing.
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Pedantic: While anyone familiar with Python knows what negative indexing is, if you want to be precise you should define a negative index.

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Done.

// A negative index starts counting from the tail of the Path such that -1
// refers to the last step, -2 refers to the second-to-last step, and so on.
// If index is invalid, this returns a non-nil PathStep that reports a nil Type.
func (pa Path) Index(i int) PathStep {
if i < 0 {
i = len(pa) + i
}
if i < 0 || i >= len(pa) {
return pathStep{}
}
return pathStep{}
return pa[i]
}

// String returns the simplified path to a node.
Expand Down