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text/template: compare reflect.Value instances differently

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To avoid false positives from the reflectvaluecompare checker #43993

Use v.IsValid() instead of

var zero reflect.Value
v != zero

Also avoid comparing directly with the singleton reflect.Value
representing a missing value. Detect the missing value by type instead.

Change-Id: I3a00d63cf61c077e7c7ae816474aa1f032be325b
Reviewed-on: https://go-review.googlesource.com/c/go/+/308769
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Keith Randall <khr@golang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Ian Lance Taylor <iant@google.com>
This commit is contained in:
Keith Randall 2021-04-08 17:06:29 -07:00 committed by Daniel Martí
parent 8d57f4dcef
commit 9a9aad449f
2 changed files with 11 additions and 5 deletions
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14
src/text/template/exec.go
View File

@ -94,6 +94,12 @@ type missingValType struct{}
var missingVal = reflect.ValueOf(missingValType{}) var missingVal = reflect.ValueOf(missingValType{})
var missingValReflectType = reflect.TypeOf(missingValType{})
func isMissing(v reflect.Value) bool {
return v.IsValid() && v.Type() == missingValReflectType
}
// at marks the state to be on node n, for error reporting. // at marks the state to be on node n, for error reporting.
func (s *state) at(node parse.Node) { func (s *state) at(node parse.Node) {
s.node = node s.node = node
@ -471,7 +477,7 @@ func (s *state) evalPipeline(dot reflect.Value, pipe *parse.PipeNode) (value ref
} }
func (s *state) notAFunction(args []parse.Node, final reflect.Value) { func (s *state) notAFunction(args []parse.Node, final reflect.Value) {
if len(args) > 1 || final != missingVal { if len(args) > 1 || !isMissing(final) {
s.errorf("can't give argument to non-function %s", args[0]) s.errorf("can't give argument to non-function %s", args[0])
} }
} }
@ -629,7 +635,7 @@ func (s *state) evalField(dot reflect.Value, fieldName string, node parse.Node,
if method := ptr.MethodByName(fieldName); method.IsValid() { if method := ptr.MethodByName(fieldName); method.IsValid() {
return s.evalCall(dot, method, false, node, fieldName, args, final) return s.evalCall(dot, method, false, node, fieldName, args, final)
} }
hasArgs := len(args) > 1 || final != missingVal hasArgs := len(args) > 1 || !isMissing(final)
// It's not a method; must be a field of a struct or an element of a map. // It's not a method; must be a field of a struct or an element of a map.
switch receiver.Kind() { switch receiver.Kind() {
case reflect.Struct: case reflect.Struct:
@ -700,7 +706,7 @@ func (s *state) evalCall(dot, fun reflect.Value, isBuiltin bool, node parse.Node
} }
typ := fun.Type() typ := fun.Type()
numIn := len(args) numIn := len(args)
if final != missingVal { if !isMissing(final) {
numIn++ numIn++
} }
numFixed := len(args) numFixed := len(args)
@ -763,7 +769,7 @@ func (s *state) evalCall(dot, fun reflect.Value, isBuiltin bool, node parse.Node
} }
} }
// Add final value if necessary. // Add final value if necessary.
if final != missingVal { if !isMissing(final) {
t := typ.In(typ.NumIn() - 1) t := typ.In(typ.NumIn() - 1)
if typ.IsVariadic() { if typ.IsVariadic() {
if numIn-1 < numFixed { if numIn-1 < numFixed {

2
src/text/template/funcs.go
View File

@ -438,7 +438,7 @@ func basicKind(v reflect.Value) (kind, error) {
// isNil returns true if v is the zero reflect.Value, or nil of its type. // isNil returns true if v is the zero reflect.Value, or nil of its type.
func isNil(v reflect.Value) bool { func isNil(v reflect.Value) bool {
if v == zero { if !v.IsValid() {
return true return true
} }
switch v.Kind() { switch v.Kind() {