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Add support for function callbacks as the target of EvaluateExpr #246

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merged 1 commit into from
Mar 26, 2023
Merged

Add support for function callbacks as the target of EvaluateExpr #246

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48 changes: 43 additions & 5 deletions helper/runner.go
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Original file line number Diff line number Diff line change
@@ -1,8 +1,10 @@
package helper

import (
"errors"
"fmt"
"os"
"reflect"

"github.com/hashicorp/hcl/v2"
"github.com/hashicorp/hcl/v2/hclsyntax"
Expand Down Expand Up @@ -196,9 +198,45 @@ func (r *Runner) DecodeRuleConfig(name string, ret interface{}) error {
return nil
}

var errRefTy = reflect.TypeOf((*error)(nil)).Elem()

// EvaluateExpr returns a value of the passed expression.
// Note that some features are limited
func (r *Runner) EvaluateExpr(expr hcl.Expression, ret interface{}, opts *tflint.EvaluateExprOption) error {
func (r *Runner) EvaluateExpr(expr hcl.Expression, target interface{}, opts *tflint.EvaluateExprOption) error {
var callback bool
rval := reflect.ValueOf(target)
rty := rval.Type()
// Callback must meet the following requirements:
// - It must be a function
// - It must take an argument
// - It must return an error
if rty.Kind() == reflect.Func && rty.NumIn() == 1 && rty.NumOut() == 1 && rty.Out(0).Implements(errRefTy) {
callback = true
target = reflect.New(rty.In(0)).Interface()
}

err := r.evaluateExpr(expr, target, opts)
if !callback {
// error should be handled in the caller
return err
}

if err != nil {
// If it cannot be represented as a Go value, exit without invoking the callback rather than returning an error.
if errors.Is(err, tflint.ErrUnknownValue) || errors.Is(err, tflint.ErrNullValue) || errors.Is(err, tflint.ErrSensitive) || errors.Is(err, tflint.ErrUnevaluable) {
return nil
}
return err
}

rerr := rval.Call([]reflect.Value{reflect.ValueOf(target).Elem()})
if rerr[0].IsNil() {
return nil
}
return rerr[0].Interface().(error)
}

func (r *Runner) evaluateExpr(expr hcl.Expression, target interface{}, opts *tflint.EvaluateExprOption) error {
if opts == nil {
opts = &tflint.EvaluateExprOption{}
}
Expand All @@ -207,7 +245,7 @@ func (r *Runner) EvaluateExpr(expr hcl.Expression, ret interface{}, opts *tflint
if opts.WantType != nil {
ty = *opts.WantType
} else {
switch ret.(type) {
switch target.(type) {
case *string, string:
ty = cty.String
case *int, int:
Expand All @@ -223,7 +261,7 @@ func (r *Runner) EvaluateExpr(expr hcl.Expression, ret interface{}, opts *tflint
case cty.Value, *cty.Value:
ty = cty.DynamicPseudoType
default:
return fmt.Errorf("unsupported result type: %T", ret)
return fmt.Errorf("unsupported target type: %T", target)
}
}

Expand Down Expand Up @@ -251,7 +289,7 @@ func (r *Runner) EvaluateExpr(expr hcl.Expression, ret interface{}, opts *tflint
return err
}

return gocty.FromCtyValue(val, ret)
return gocty.FromCtyValue(val, target)
}

// EmitIssue adds an issue to the runner itself.
Expand All @@ -266,7 +304,7 @@ func (r *Runner) EmitIssue(rule tflint.Rule, message string, location hcl.Range)

// EnsureNoError is a method that simply runs a function if there is no error.
//
// Deprecated: Use errors.Is() instead to determine which errors can be ignored.
// Deprecated: Use EvaluateExpr with a function callback. e.g. EvaluateExpr(expr, func (val T) error {}, ...)
func (r *Runner) EnsureNoError(err error, proc func() error) error {
if err == nil {
return proc()
Expand Down
11 changes: 11 additions & 0 deletions helper/runner_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -576,6 +576,7 @@ resource "aws_instance" "foo" {
}

for _, resource := range resources.Blocks {
// raw value
var instanceType string
if err := runner.EvaluateExpr(resource.Body.Attributes["instance_type"].Expr, &instanceType, nil); err != nil {
t.Fatal(err)
Expand All @@ -584,6 +585,16 @@ resource "aws_instance" "foo" {
if instanceType != test.Want {
t.Fatalf(`"%s" is expected, but got "%s"`, test.Want, instanceType)
}

// callback
if err := runner.EvaluateExpr(resource.Body.Attributes["instance_type"].Expr, func(val string) error {
if instanceType != test.Want {
t.Fatalf(`"%s" is expected, but got "%s"`, test.Want, instanceType)
}
return nil
}, nil); err != nil {
t.Fatal(err)
}
}
})
}
Expand Down
49 changes: 44 additions & 5 deletions plugin/plugin2host/client.go
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@ import (
"errors"
"fmt"
"os"
"reflect"
"strings"

"github.com/hashicorp/hcl/v2"
Expand Down Expand Up @@ -274,8 +275,46 @@ func (c *GRPCClient) DecodeRuleConfig(name string, ret interface{}) error {
return nil
}

var errRefTy = reflect.TypeOf((*error)(nil)).Elem()

// EvaluateExpr evals the passed expression based on the type.
func (c *GRPCClient) EvaluateExpr(expr hcl.Expression, ret interface{}, opts *tflint.EvaluateExprOption) error {
// Passing a callback function instead of a value as the target will invoke the callback,
// passing the evaluated value to the argument.
func (c *GRPCClient) EvaluateExpr(expr hcl.Expression, target interface{}, opts *tflint.EvaluateExprOption) error {
var callback bool
rval := reflect.ValueOf(target)
rty := rval.Type()
// Callback must meet the following requirements:
// - It must be a function
// - It must take an argument
// - It must return an error
if rty.Kind() == reflect.Func && rty.NumIn() == 1 && rty.NumOut() == 1 && rty.Out(0).Implements(errRefTy) {
callback = true
target = reflect.New(rty.In(0)).Interface()
}

err := c.evaluateExpr(expr, target, opts)
if !callback {
// error should be handled in the caller
return err
}

if err != nil {
// If it cannot be represented as a Go value, exit without invoking the callback rather than returning an error.
if errors.Is(err, tflint.ErrUnknownValue) || errors.Is(err, tflint.ErrNullValue) || errors.Is(err, tflint.ErrSensitive) || errors.Is(err, tflint.ErrUnevaluable) {
return nil
}
return err
}

rerr := rval.Call([]reflect.Value{reflect.ValueOf(target).Elem()})
if rerr[0].IsNil() {
return nil
}
return rerr[0].Interface().(error)
}

func (c *GRPCClient) evaluateExpr(expr hcl.Expression, target interface{}, opts *tflint.EvaluateExprOption) error {
if opts == nil {
opts = &tflint.EvaluateExprOption{}
}
Expand All @@ -284,7 +323,7 @@ func (c *GRPCClient) EvaluateExpr(expr hcl.Expression, ret interface{}, opts *tf
if opts.WantType != nil {
ty = *opts.WantType
} else {
switch ret.(type) {
switch target.(type) {
case *string, string:
ty = cty.String
case *int, int:
Expand All @@ -300,7 +339,7 @@ func (c *GRPCClient) EvaluateExpr(expr hcl.Expression, ret interface{}, opts *tf
case cty.Value, *cty.Value:
ty = cty.DynamicPseudoType
default:
panic(fmt.Sprintf("unsupported result type: %T", ret))
panic(fmt.Sprintf("unsupported target type: %T", target))
}
}
tyby, err := json.MarshalType(ty)
Expand Down Expand Up @@ -332,7 +371,7 @@ func (c *GRPCClient) EvaluateExpr(expr hcl.Expression, ret interface{}, opts *tf
}

if ty == cty.DynamicPseudoType {
return gocty.FromCtyValue(val, ret)
return gocty.FromCtyValue(val, target)
}

// Returns an error if the value cannot be decoded to a Go value (e.g. unknown, null, sensitive).
Expand All @@ -356,7 +395,7 @@ func (c *GRPCClient) EvaluateExpr(expr hcl.Expression, ret interface{}, opts *tf
return err
}

return gocty.FromCtyValue(val, ret)
return gocty.FromCtyValue(val, target)
}

// EmitIssue emits the issue with the passed rule, message, location
Expand Down
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