builder,cli-tests: var_exists() function.

Signed-off-by: Erik Hollensbe <github@hollensbe.org>

builder/command/funcs.go

@@ -9,15 +9,19 @@ import (
 	"github.com/pkg/errors"
 )
 
+// VarExists corresponds to the `var_exists` func.
+func (i *Interpreter) VarExists(key string) bool {
+	_, ok := i.vars[key]
+	return ok
+}
+
 // Var corresponds to the `var` func.
 func (i *Interpreter) Var(key string) (string, error) {
 	val, ok := i.vars[key]
 	if !ok {
 		return "", fmt.Errorf("value for key %q does not exist", key)
 	}
 
-	fmt.Println(val)
-
 	return val, nil
 }
 

builder/evaluator/mruby/funcs.go

@@ -16,17 +16,30 @@ type funcFunc func(args []*gm.MrbValue, self *gm.MrbValue) (gm.Value, gm.Value)
 
 func (m *MRuby) funcJumpTable() map[string]*funcDefinition {
 	return map[string]*funcDefinition{
-		"var":    {m.varFunc, gm.ArgsReq(1)},
-		"import": {m.importFunc, gm.ArgsReq(1)},
-		"save":   {m.saveFunc, gm.ArgsReq(1)},
-		"getenv": {m.getenv, gm.ArgsReq(1)},
-		"getuid": {m.getuid, gm.ArgsReq(1)},
-		"getgid": {m.getgid, gm.ArgsReq(1)},
-		"read":   {m.read, gm.ArgsReq(1)},
-		"skip":   {m.skip, gm.ArgsNone() | gm.ArgsBlock()},
+		"var_exists": {m.varExistsFunc, gm.ArgsReq(1)},
+		"var":        {m.varFunc, gm.ArgsReq(1)},
+		"import":     {m.importFunc, gm.ArgsReq(1)},
+		"save":       {m.saveFunc, gm.ArgsReq(1)},
+		"getenv":     {m.getenv, gm.ArgsReq(1)},
+		"getuid":     {m.getuid, gm.ArgsReq(1)},
+		"getgid":     {m.getgid, gm.ArgsReq(1)},
+		"read":       {m.read, gm.ArgsReq(1)},
+		"skip":       {m.skip, gm.ArgsNone() | gm.ArgsBlock()},
 	}
 }
 
+func (m *MRuby) varExistsFunc(args []*gm.MrbValue, self *gm.MrbValue) (gm.Value, gm.Value) {
+	if err := checkArgs(args, 1); err != nil {
+		return nil, m.createException(err)
+	}
+
+	if m.Interp.VarExists(args[0].String()) {
+		return m.mrb.TrueValue(), nil
+	}
+
+	return m.mrb.FalseValue(), nil
+}
+
 func (m *MRuby) varFunc(args []*gm.MrbValue, self *gm.MrbValue) (gm.Value, gm.Value) {
 	if err := checkArgs(args, 1); err != nil {
 		return nil, m.createException(err)

cli-tests/vars_test.go

@@ -36,4 +36,15 @@ func (s *cliSuite) TestVars(c *C) {
 
 	c.Assert(err, IsNil)
 	checkFailure(c, cmd)
+
+	cmd, err = build(`
+    from "debian"
+		copy ".", "."
+		if var_exists("testfile")
+			run "test -f #{var("testfile")}"
+		end
+	`, "-n")
+
+	c.Assert(err, IsNil)
+	checkSuccess(c, cmd)
 }