lang: core, funcs, types: Add ctx to simple func

Plumb through the standard context.Context so that a function can be
cancelled if someone requests this. It makes it less awkward to write
simple functions that might depend on io or network access.

lang/core/example/answer_func.go

@@ -30,6 +30,8 @@
 package coreexample
 
 import (
+	"context"
+
 	"github.com/purpleidea/mgmt/lang/funcs/simple"
 	"github.com/purpleidea/mgmt/lang/types"
 )
@@ -40,7 +42,7 @@ const Answer = 42
 func init() {
 	simple.ModuleRegister(ModuleName, "answer", &types.FuncValue{
 		T: types.NewType("func() int"),
-		V: func([]types.Value) (types.Value, error) {
+		V: func(context.Context, []types.Value) (types.Value, error) {
 			return &types.IntValue{V: Answer}, nil
 		},
 	})

lang/core/example/errorbool_func.go

@@ -30,6 +30,7 @@
 package coreexample
 
 import (
+	"context"
 	"fmt"
 
 	"github.com/purpleidea/mgmt/lang/funcs/simple"
@@ -39,7 +40,7 @@ import (
 func init() {
 	simple.ModuleRegister(ModuleName, "errorbool", &types.FuncValue{
 		T: types.NewType("func(a bool) str"),
-		V: func(input []types.Value) (types.Value, error) {
+		V: func(ctx context.Context, input []types.Value) (types.Value, error) {
 			if input[0].Bool() {
 				return nil, fmt.Errorf("we errored on request")
 			}

lang/core/example/int2str_func.go

@@ -30,6 +30,7 @@
 package coreexample
 
 import (
+	"context"
 	"fmt"
 
 	"github.com/purpleidea/mgmt/lang/funcs/simple"
@@ -39,7 +40,7 @@ import (
 func init() {
 	simple.ModuleRegister(ModuleName, "int2str", &types.FuncValue{
 		T: types.NewType("func(a int) str"),
-		V: func(input []types.Value) (types.Value, error) {
+		V: func(ctx context.Context, input []types.Value) (types.Value, error) {
 			return &types.StrValue{
 				V: fmt.Sprintf("%d", input[0].Int()),
 			}, nil

lang/core/example/nested/hello_func.go

@@ -30,6 +30,8 @@
 package corenested
 
 import (
+	"context"
+
 	coreexample "github.com/purpleidea/mgmt/lang/core/example"
 	"github.com/purpleidea/mgmt/lang/funcs/simple"
 	"github.com/purpleidea/mgmt/lang/types"
@@ -43,7 +45,7 @@ func init() {
 }
 
 // Hello returns some string. This is just to test nesting.
-func Hello(input []types.Value) (types.Value, error) {
+func Hello(ctx context.Context, input []types.Value) (types.Value, error) {
 	return &types.StrValue{
 		V: "Hello!",
 	}, nil

lang/core/example/plus_func.go

@@ -30,6 +30,8 @@
 package coreexample
 
 import (
+	"context"
+
 	"github.com/purpleidea/mgmt/lang/funcs/simple"
 	"github.com/purpleidea/mgmt/lang/types"
 )
@@ -42,7 +44,7 @@ func init() {
 }
 
 // Plus returns y + z.
-func Plus(input []types.Value) (types.Value, error) {
+func Plus(ctx context.Context, input []types.Value) (types.Value, error) {
 	y, z := input[0].Str(), input[1].Str()
 	return &types.StrValue{
 		V: y + z,

lang/core/example/str2int_func.go

@@ -30,6 +30,7 @@
 package coreexample
 
 import (
+	"context"
 	"strconv"
 
 	"github.com/purpleidea/mgmt/lang/funcs/simple"
@@ -39,7 +40,7 @@ import (
 func init() {
 	simple.ModuleRegister(ModuleName, "str2int", &types.FuncValue{
 		T: types.NewType("func(a str) int"),
-		V: func(input []types.Value) (types.Value, error) {
+		V: func(ctx context.Context, input []types.Value) (types.Value, error) {
 			var i int64
 			if val, err := strconv.ParseInt(input[0].Str(), 10, 64); err == nil {
 				i = val