Add a Builtin AST node

Author: FollowTheProcess

internal/syntax/ast/ast_test.go

@@ -56,6 +56,17 @@ func TestNode(t *testing.T) {
 			end:   token.Token{Kind: token.Ident, Start: 0, End: 4},
 			kind:  ast.KindIdent,
 		},
+		{
+			name: "builtin",
+			node: ast.Ident{
+				Name:  "test",
+				Token: token.Token{Kind: token.Ident, Start: 0, End: 4},
+				Type:  ast.KindBuiltin,
+			},
+			start: token.Token{Kind: token.Ident, Start: 0, End: 4},
+			end:   token.Token{Kind: token.Ident, Start: 0, End: 4},
+			kind:  ast.KindBuiltin,
+		},
 		{
 			name: "var statement",
 			// @variable = sometext

internal/syntax/ast/expression.go

@@ -40,6 +40,44 @@ func (i Ident) Kind() Kind {
 // statementNode marks an [Ident] as an [ast.Expression].
 func (i Ident) expressionNode() {}
 
+// Builtin is a built in identifier, prefixed with a '$'.
+//
+// E.g. 'uuid' is a perfectly fine identifier for any user to use for a variable
+// but '$uuid' is a builtin that returns a random UUIDv4.
+//
+// The Builtin AST node is functionality identical to an [Ident], but must
+// be separate to allow differentiating builtins from regular idents.
+type Builtin struct {
+	// Name is the ident's name.
+	Name string `yaml:"name"`
+
+	// The [token.Ident] token.
+	Token token.Token `yaml:"token"`
+
+	// Type is the kind of ast node, in this case [KindBuiltin].
+	Type Kind `yaml:"type"`
+}
+
+// Start returns the first meaningful token in the Builtin, which is
+// the [token.Ident].
+func (b Builtin) Start() token.Token {
+	return b.Token
+}
+
+// End returns the last token in the Builtin, which is also
+// the [token.Ident].
+func (b Builtin) End() token.Token {
+	return b.Token
+}
+
+// Kind returns [KindBuiltin].
+func (b Builtin) Kind() Kind {
+	return b.Type
+}
+
+// statementNode marks a [Builtin] as an [ast.Expression].
+func (b Builtin) expressionNode() {}
+
 // TextLiteral is a literal text expression.
 type TextLiteral struct {
 	// The text value (unquoted)

internal/syntax/ast/kind.go

@@ -11,6 +11,7 @@ const (
 	KindFile                               // File
 	KindVarStatement                       // VarStatement
 	KindIdent                              // Ident
+	KindBuiltin                            // Builtin
 	KindTextLiteral                        // TextLiteral
 	KindInterp                             // Interp
 	KindPrompt                             // Prompt

internal/syntax/ast/kind_string.go

@@ -15,6 +15,13 @@ import (
 	"go.followtheprocess.codes/zap/internal/zap"
 )
 
+// TODO(@FollowTheProcess): This is getting unwieldy and is a bit beyond what testscript is designed for
+//
+// Once I have builtins and selector expressions working, the http files will be able to
+// do e.g. '@base = {{ $env.TEST_SERVER_URL }}' and then I can host a local httpbin in
+// a testcontainer or even just create a simple inline server for the tests and it'll
+// be much nicer! :)
+
 var update = flag.Bool("update", false, "Update testscript snapshots")
 
 func TestMain(m *testing.M) {