bake: new hclparser package

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

bake/hclparser/expr.go

@@ -0,0 +1,153 @@
+package hclparser
+
+import (
+	"reflect"
+	"unsafe"
+
+	"github.com/hashicorp/hcl/v2"
+	"github.com/hashicorp/hcl/v2/hclsyntax"
+	"github.com/pkg/errors"
+)
+
+func funcCalls(exp hcl.Expression) ([]string, hcl.Diagnostics) {
+	node, ok := exp.(hclsyntax.Node)
+	if !ok {
+		fns, err := jsonFuncCallsRecursive(exp)
+		if err != nil {
+			return nil, hcl.Diagnostics{
+				&hcl.Diagnostic{
+					Severity: hcl.DiagError,
+					Summary:  "Invalid expression",
+					Detail:   err.Error(),
+					Subject:  exp.Range().Ptr(),
+					Context:  exp.Range().Ptr(),
+				},
+			}
+		}
+		return fns, nil
+	}
+
+	var funcnames []string
+	hcldiags := hclsyntax.VisitAll(node, func(n hclsyntax.Node) hcl.Diagnostics {
+		if fe, ok := n.(*hclsyntax.FunctionCallExpr); ok {
+			funcnames = append(funcnames, fe.Name)
+		}
+		return nil
+	})
+	if hcldiags.HasErrors() {
+		return nil, hcldiags
+	}
+	return funcnames, nil
+}
+
+func jsonFuncCallsRecursive(exp hcl.Expression) ([]string, error) {
+	je, ok := exp.(jsonExp)
+	if !ok {
+		return nil, errors.Errorf("invalid expression type %T", exp)
+	}
+	m := map[string]struct{}{}
+	for _, e := range elementExpressions(je, exp) {
+		if err := appendJSONFuncCalls(e, m); err != nil {
+			return nil, err
+		}
+	}
+	arr := make([]string, 0, len(m))
+	for n := range m {
+		arr = append(arr, n)
+	}
+	return arr, nil
+}
+
+func appendJSONFuncCalls(exp hcl.Expression, m map[string]struct{}) error {
+	v := reflect.ValueOf(exp)
+	if v.Kind() != reflect.Ptr || v.IsNil() {
+		return errors.Errorf("invalid json expression kind %T %v", exp, v.Kind())
+	}
+	src := v.Elem().FieldByName("src")
+	if src.IsZero() {
+		return errors.Errorf("%v has no property src", v.Elem().Type())
+	}
+	if src.Kind() != reflect.Interface {
+		return errors.Errorf("%v src is not interface: %v", src.Type(), src.Kind())
+	}
+	src = src.Elem()
+	if src.IsNil() {
+		return nil
+	}
+	if src.Kind() == reflect.Ptr {
+		src = src.Elem()
+	}
+	if src.Kind() != reflect.Struct {
+		return errors.Errorf("%v is not struct: %v", src.Type(), src.Kind())
+	}
+
+	// hcl/v2/json/ast#stringVal
+	val := src.FieldByName("Value")
+	if val.IsZero() {
+		return nil
+	}
+	rng := src.FieldByName("SrcRange")
+	if val.IsZero() {
+		return nil
+	}
+	var stringVal struct {
+		Value    string
+		SrcRange hcl.Range
+	}
+
+	if !val.Type().AssignableTo(reflect.ValueOf(stringVal.Value).Type()) {
+		return nil
+	}
+	if !rng.Type().AssignableTo(reflect.ValueOf(stringVal.SrcRange).Type()) {
+		return nil
+	}
+	// reflect.Set does not work for unexported fields
+	stringVal.Value = *(*string)(unsafe.Pointer(val.UnsafeAddr()))
+	stringVal.SrcRange = *(*hcl.Range)(unsafe.Pointer(rng.UnsafeAddr()))
+
+	expr, diags := hclsyntax.ParseExpression([]byte(stringVal.Value), stringVal.SrcRange.Filename, stringVal.SrcRange.Start)
+	if diags.HasErrors() {
+		return nil
+	}
+
+	fns, err := funcCalls(expr)
+	if err != nil {
+		return err
+	}
+
+	for _, fn := range fns {
+		m[fn] = struct{}{}
+	}
+
+	return nil
+}
+
+type jsonExp interface {
+	ExprList() []hcl.Expression
+	ExprMap() []hcl.KeyValuePair
+}
+
+func elementExpressions(je jsonExp, exp hcl.Expression) []hcl.Expression {
+	list := je.ExprList()
+	if len(list) != 0 {
+		exp := make([]hcl.Expression, 0, len(list))
+		for _, e := range list {
+			if je, ok := e.(jsonExp); ok {
+				exp = append(exp, elementExpressions(je, e)...)
+			}
+		}
+		return exp
+	}
+	kvlist := je.ExprMap()
+	if len(kvlist) != 0 {
+		exp := make([]hcl.Expression, 0, len(kvlist)*2)
+		for _, p := range kvlist {
+			exp = append(exp, p.Key)
+			if je, ok := p.Value.(jsonExp); ok {
+				exp = append(exp, elementExpressions(je, p.Value)...)
+			}
+		}
+		return exp
+	}
+	return []hcl.Expression{exp}
+}