Add support for string | run(...) to set stdin (#238)

* Add support for `string | run(...)` to set stdin

* Fix lint

* make test more likely work across os

* try#2 at wc output check

eval/eval.go

@@ -220,6 +220,10 @@ func (s *State) evalInternal(node any) object.Object { //nolint:funlen,gocognit,
 		if node.Token.Type() == token.OR && left == object.TRUE {
 			return object.TRUE
 		}
+		// Pipe operator, for now only for string | call expressions:
+		if node.Token.Type() == token.BITOR && left.Type() == object.STRING && node.Right.Value().Type() == token.LPAREN {
+			return s.evalPipe(left, node.Right)
+		}
 		right := s.Eval(node.Right)
 		if right.Type() == object.ERROR {
 			return right
@@ -308,6 +312,13 @@ func (s *State) evalInternal(node any) object.Object { //nolint:funlen,gocognit,
 	return s.Errorf("unknown node type: %T", node)
 }
 
+func (s *State) evalPipe(left object.Object, right ast.Node) object.Object {
+	s.PipeVal = []byte(left.(object.String).Value)
+	res := s.evalInternal(right)
+	s.PipeVal = nil
+	return res
+}
+
 func (s *State) evalIndexExpression(left object.Object, node *ast.IndexExpression) object.Object {
 	if left.Type() == object.ERROR {
 		return left

eval/eval_api.go

@@ -47,6 +47,7 @@ type State struct {
 	// To enforce a max duration or cancel evals.
 	Context context.Context //nolint:containedctx // we need a context for callbacks from extensions and to set it without API change.
 	Cancel  context.CancelFunc
+	PipeVal []byte // value to return from pipe() function
 }
 
 func NewState() *State {
@@ -217,3 +218,7 @@ func (s *State) NumMacros() int {
 }
 
 // TriggerNoCache() is replaced by DontCache boolean in object.Extension.
+
+func (s *State) GetPipeValue() []byte {
+	return s.PipeVal
+}

extensions/shell.go

@@ -45,6 +45,9 @@ func createShellFunctions() {
 			var sout, serr bytes.Buffer
 			cmd.Stdout = &sout
 			cmd.Stderr = &serr
+			if obj := s.GetPipeValue(); obj != nil {
+				cmd.Stdin = bytes.NewReader(obj)
+			}
 			err := cmd.Run()
 			res := object.MakeQuad(stdout, object.String{Value: sout.String()},
 				stderr, object.String{Value: serr.String()})

tests/shell.gr

@@ -7,3 +7,4 @@ IsErr("non zero exit", run("false"), "exit status 1")
 NoErr("exec captures", exec("false").err, `^exit status 1$`)
 NoErr("exec captures", exec("echo", "-n", "foo").stdout, "^foo$")
 NoErr("exec captures", exec("ls", "/no/such/file").stderr, "No such file or directory")
+NoErr("pipe exec", ("abcde" | exec("wc", "-c")).stdout, "5\n$") // wc output dffers on different systems