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Ignoring fields with struct tag expr:"-" and make "in" return false for unexported fields #806

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Ignoring fields with struct tag expr:"-" and make "in" return false for unexported fields #806

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401009f
allow ignoring struct member using a - in expr struct tag
diegommm Jun 24, 2025
6bd3eb5
fix in operator
diegommm Jun 24, 2025
56d0528
simplify logic
diegommm Jun 27, 2025
eecf371
add regression test for #807
diegommm Jun 27, 2025
1089aa9
fixes #807: make in operator return false for unexported struct fields
diegommm Jun 27, 2025
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5 changes: 3 additions & 2 deletions builtin/lib.go
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Original file line number Diff line number Diff line change
Expand Up @@ -421,10 +421,11 @@ func get(params ...any) (out any, err error) {
fieldName := i.(string)
value := v.FieldByNameFunc(func(name string) bool {
field, _ := v.Type().FieldByName(name)
if field.Tag.Get("expr") == fieldName {
tagName := field.Tag.Get("expr")
if tagName == fieldName {
return true
}
return name == fieldName
return tagName != "-" && name == fieldName
})
if value.IsValid() {
return value.Interface(), nil
Expand Down
16 changes: 12 additions & 4 deletions checker/nature/utils.go
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Original file line number Diff line number Diff line change
Expand Up @@ -7,10 +7,14 @@ import (
)

func fieldName(field reflect.StructField) string {
if taggedName := field.Tag.Get("expr"); taggedName != "" {
switch taggedName := field.Tag.Get("expr"); taggedName {
case "-":
return ""
case "":
return field.Name
default:
return taggedName
}
return field.Name
}

func fetchField(t reflect.Type, name string) (reflect.StructField, bool) {
Expand All @@ -23,7 +27,7 @@ func fetchField(t reflect.Type, name string) (reflect.StructField, bool) {
for i := 0; i < t.NumField(); i++ {
field := t.Field(i)
// Search all fields, even embedded structs.
if fieldName(field) == name {
if n := fieldName(field); n != "" && n == name {
return field, true
}
}
Expand Down Expand Up @@ -69,7 +73,11 @@ func StructFields(t reflect.Type) map[string]Nature {
}
}

table[fieldName(f)] = Nature{
name := fieldName(f)
if name == "" {
continue
}
table[name] = Nature{
Type: f.Type,
FieldIndex: f.Index,
}
Expand Down
69 changes: 67 additions & 2 deletions expr_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@ import (
"fmt"
"os"
"reflect"
"strings"
"sync"
"testing"
"time"
Expand Down Expand Up @@ -139,7 +140,71 @@ func ExampleEnv_tagged_field_names() {

fmt.Printf("%v", output)

// Output : Hello World
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This is unrelated but I realized that this example test was not being run because there is a space between Output and :, so I removed the space and the example test is now running and is successful.

// Output: Hello World
}

func ExampleEnv_hidden_tagged_field_names() {
type Internal struct {
Visible string
Hidden string `expr:"-"`
}
type environment struct {
Visible string
Hidden string `expr:"-"`
HiddenInternal Internal `expr:"-"`
VisibleInternal Internal
}

env := environment{
Hidden: "First level secret",
HiddenInternal: Internal{
Visible: "Second level secret",
Hidden: "Also hidden",
},
VisibleInternal: Internal{
Visible: "Not a secret",
Hidden: "Hidden too",
},
}

hiddenValues := []string{
`Hidden`,
`HiddenInternal`,
`HiddenInternal.Visible`,
`HiddenInternal.Hidden`,
`VisibleInternal.Hidden`,
}
for _, expression := range hiddenValues {
output, err := expr.Eval(expression, env)
if err == nil || !strings.Contains(err.Error(), "cannot fetch") {
fmt.Printf("unexpected output: %v; err: %v\n", output, err)
return
}
fmt.Printf("%q is hidden as expected\n", expression)
}

visibleValues := []string{
`Visible`,
`VisibleInternal`,
`VisibleInternal.Visible`,
}
for _, expression := range visibleValues {
_, err := expr.Eval(expression, env)
if err != nil {
fmt.Printf("unexpected error: %v\n", err)
return
}
fmt.Printf("%q is visible as expected\n", expression)
}

// Output: "Hidden" is hidden as expected
// "HiddenInternal" is hidden as expected
// "HiddenInternal.Visible" is hidden as expected
// "HiddenInternal.Hidden" is hidden as expected
// "VisibleInternal.Hidden" is hidden as expected
// "Visible" is visible as expected
// "VisibleInternal" is visible as expected
// "VisibleInternal.Visible" is visible as expected
}

func ExampleAsKind() {
Expand Down Expand Up @@ -529,7 +594,7 @@ func ExamplePatch() {
}
fmt.Printf("%v", output)

// Output : Hello, you, world!
// Output: Hello, you, world!
Comment on lines -532 to +612
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Same as above: this is unrelated but I realized that this example test was not being run because there is a space between Output and :, so I removed the space and the example test is now running and is successful.

}

func ExampleWithContext() {
Expand Down
5 changes: 3 additions & 2 deletions vm/runtime/runtime.go
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Original file line number Diff line number Diff line change
Expand Up @@ -65,10 +65,11 @@ func Fetch(from, i any) any {
fieldName := i.(string)
value := v.FieldByNameFunc(func(name string) bool {
field, _ := v.Type().FieldByName(name)
if field.Tag.Get("expr") == fieldName {
tagName := field.Tag.Get("expr")
if tagName == fieldName {
return true
}
return name == fieldName
return tagName != "-" && name == fieldName
})
if value.IsValid() {
return value.Interface()
Expand Down