Added support of ignoring expression results in variable declaration …

…using '_' as a variable name
MontFerret · Sep 20, 2021 · 7dea258 · 7dea258
1 parent f52b5db
commit 7dea258
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Showing 14 changed files with 1,018 additions and 914 deletions.
diff --git a/pkg/compiler/compiler_let_test.go b/pkg/compiler/compiler_let_test.go
@@ -337,4 +337,41 @@ func TestLet(t *testing.T) {
 		So(err, ShouldBeNil)
 		So(string(out), ShouldEqual, `false`)
 	})
+
+	Convey("Should use ignorable variable name", t, func() {
+		out, err := newCompilerWithObservable().MustCompile(`
+			LET _ = (FOR i IN 1..100 RETURN NONE)
+
+			RETURN TRUE
+		`).Run(context.Background())
+
+		So(err, ShouldBeNil)
+		So(string(out), ShouldEqual, `true`)
+	})
+
+	Convey("Should allow to declare a variable name using _", t, func() {
+		c := compiler.New()
+
+		out, err := c.MustCompile(`
+			LET _ = (FOR i IN 1..100 RETURN NONE)
+			LET _ = (FOR i IN 1..100 RETURN NONE)
+
+			RETURN TRUE
+		`).Run(context.Background())
+
+		So(err, ShouldBeNil)
+		So(string(out), ShouldEqual, `true`)
+	})
+
+	Convey("Should not allow to use ignorable variable name", t, func() {
+		c := compiler.New()
+
+		_, err := c.Compile(`
+			LET _ = (FOR i IN 1..100 RETURN NONE)
+
+			RETURN _
+		`)
+
+		So(err, ShouldNotBeNil)
+	})
 }
diff --git a/pkg/compiler/scope.go b/pkg/compiler/scope.go
@@ -55,6 +55,10 @@ func (s *scope) HasVariable(name string) bool {
 }
 
 func (s *scope) SetVariable(name string) error {
+	if name == core.IgnorableVariable {
+		return nil
+	}
+
 	_, exists := s.vars[name]
 
 	if exists {

diff --git a/pkg/compiler/visitor.go b/pkg/compiler/visitor.go
@@ -1142,8 +1142,12 @@ func (v *visitor) doVisitVariable(ctx *fql.VariableContext, scope *scope) (core.
 func (v *visitor) doVisitVariableDeclaration(ctx *fql.VariableDeclarationContext, scope *scope) (core.Expression, error) {
 	var init core.Expression
 	var err error
+	name := core.IgnorableVariable
+
+	if id := ctx.Identifier(); id != nil {
+		name = id.GetText()
+	}
 
-	name := ctx.Identifier().GetText()
 	err = scope.SetVariable(name)
 
 	if err != nil {

diff --git a/pkg/parser/antlr/FqlLexer.g4 b/pkg/parser/antlr/FqlLexer.g4
@@ -86,6 +86,7 @@ While: 'WHILE';
 // Literals
 Param: '@';
 Identifier: Letter+ (Symbols (Identifier)*)* (Digit (Identifier)*)*;
+IgnoreIdentifier: Underscore;
 StringLiteral: SQString | DQSring | BacktickString | TickString;
 IntegerLiteral: [0-9]+;
 FloatLiteral
@@ -111,7 +112,8 @@ fragment ExponentPart
 fragment Letter
     : 'A'..'Z' | 'a'..'z'
     ;
-fragment Symbols: '_';
+fragment Symbols: Underscore;
+fragment Underscore: '_';
 fragment Digit
     : '0'..'9'
     ;

diff --git a/pkg/parser/antlr/FqlLexer.tokens b/pkg/parser/antlr/FqlLexer.tokens
@@ -62,11 +62,12 @@ Do=61
 While=62
 Param=63
 Identifier=64
-StringLiteral=65
-IntegerLiteral=66
-FloatLiteral=67
-NamespaceSegment=68
-UnknownIdentifier=69
+IgnoreIdentifier=65
+StringLiteral=66
+IntegerLiteral=67
+FloatLiteral=68
+NamespaceSegment=69
+UnknownIdentifier=70
 ':'=5
 ';'=6
 '.'=7

diff --git a/pkg/parser/antlr/FqlParser.g4 b/pkg/parser/antlr/FqlParser.g4
@@ -41,6 +41,7 @@ bodyExpression
 
 variableDeclaration
     : Let Identifier Assign expression
+    | Let IgnoreIdentifier Assign expression
     ;
 
 returnExpression

diff --git a/pkg/parser/fql/FqlLexer.interp b/pkg/parser/fql/FqlLexer.interp
diff --git a/pkg/parser/fql/FqlLexer.tokens b/pkg/parser/fql/FqlLexer.tokens
@@ -62,11 +62,12 @@ Do=61
 While=62
 Param=63
 Identifier=64
-StringLiteral=65
-IntegerLiteral=66
-FloatLiteral=67
-NamespaceSegment=68
-UnknownIdentifier=69
+IgnoreIdentifier=65
+StringLiteral=66
+IntegerLiteral=67
+FloatLiteral=68
+NamespaceSegment=69
+UnknownIdentifier=70
 ':'=5
 ';'=6
 '.'=7

diff --git a/pkg/parser/fql/FqlParser.interp b/pkg/parser/fql/FqlParser.interp
diff --git a/pkg/parser/fql/FqlParser.tokens b/pkg/parser/fql/FqlParser.tokens
@@ -62,11 +62,12 @@ Do=61
 While=62
 Param=63
 Identifier=64
-StringLiteral=65
-IntegerLiteral=66
-FloatLiteral=67
-NamespaceSegment=68
-UnknownIdentifier=69
+IgnoreIdentifier=65
+StringLiteral=66
+IntegerLiteral=67
+FloatLiteral=68
+NamespaceSegment=69
+UnknownIdentifier=70
 ':'=5
 ';'=6
 '.'=7

diff --git a/pkg/parser/fql/fql_lexer.go b/pkg/parser/fql/fql_lexer.go
diff --git a/pkg/parser/fql/fql_parser.go b/pkg/parser/fql/fql_parser.go
diff --git a/pkg/runtime/core/consts.go b/pkg/runtime/core/consts.go
@@ -0,0 +1,5 @@
+package core
+
+const (
+	IgnorableVariable = "_"
+)
diff --git a/pkg/runtime/core/scope.go b/pkg/runtime/core/scope.go
@@ -74,21 +74,24 @@ func newScope(root *RootScope, parent *Scope) *Scope {
 }
 
 func (s *Scope) SetVariable(name string, val Value) error {
-	_, exists := s.vars[name]
+	if name != IgnorableVariable {
+		_, exists := s.vars[name]
+
+		// it already has been declared in the current scope
+		if exists {
+			return Errorf(ErrNotUnique, "variable is already declared: '%s'", name)
+		}
 
-	// it already has been declared in the current scope
-	if exists {
-		return Errorf(ErrNotUnique, "variable is already declared: '%s'", name)
+		s.vars[name] = val
 	}
 
+	// we still want to make sure that nothing than needs to be closed leaks out
 	disposable, ok := val.(io.Closer)
 
 	if ok {
 		s.root.AddDisposable(disposable)
 	}
 
-	s.vars[name] = val
-
 	return nil
 }