FIX: TRUE and FALSE can also be functions

Previously the engine was internally transforming TRUE() to TRUE

Note that the friendly giant implements this only for
compatibility reasons

base/src/expressions/parser/mod.rs

@@ -642,7 +642,38 @@ impl Parser {
                 position: 0,
                 message: "Unexpected end of input.".to_string(),
             },
-            TokenType::Boolean(value) => Node::BooleanKind(value),
+            TokenType::Boolean(value) => {
+                // Could be a function call "TRUE()"
+                let next_token = self.lexer.peek_token();
+                if next_token == TokenType::LeftParenthesis {
+                    self.lexer.advance_token();
+                    // We parse all the arguments, although technically this is moot
+                    // But is has the upside of transforming `=TRUE( 4 )` into `=TRUE(4)`
+                    let args = match self.parse_function_args() {
+                        Ok(s) => s,
+                        Err(e) => return e,
+                    };
+                    if let Err(err) = self.lexer.expect(TokenType::RightParenthesis) {
+                        return Node::ParseErrorKind {
+                            formula: self.lexer.get_formula(),
+                            position: err.position,
+                            message: err.message,
+                        };
+                    }
+                    if value {
+                        return Node::FunctionKind {
+                            kind: Function::True,
+                            args,
+                        };
+                    } else {
+                        return Node::FunctionKind {
+                            kind: Function::False,
+                            args,
+                        };
+                    }
+                }
+                Node::BooleanKind(value)
+            }
             TokenType::Compare(_) => {
                 // A primary Node cannot start with an operator
                 Node::ParseErrorKind {

base/src/functions/logical.rs

@@ -7,6 +7,22 @@ use crate::{
 use super::util::compare_values;
 
 impl Model {
+    pub(crate) fn fn_true(&mut self, args: &[Node], cell: CellReferenceIndex) -> CalcResult {
+        if args.is_empty() {
+            CalcResult::Boolean(true)
+        } else {
+            CalcResult::new_args_number_error(cell)
+        }
+    }
+
+    pub(crate) fn fn_false(&mut self, args: &[Node], cell: CellReferenceIndex) -> CalcResult {
+        if args.is_empty() {
+            CalcResult::Boolean(false)
+        } else {
+            CalcResult::new_args_number_error(cell)
+        }
+    }
+
     pub(crate) fn fn_if(&mut self, args: &[Node], cell: CellReferenceIndex) -> CalcResult {
         if args.len() == 2 || args.len() == 3 {
             let cond_result = self.get_boolean(&args[0], cell);

base/src/functions/mod.rs

@@ -949,7 +949,7 @@ impl Model {
         match kind {
             // Logical
             Function::And => self.fn_and(args, cell),
-            Function::False => CalcResult::Boolean(false),
+            Function::False => self.fn_false(args, cell),
             Function::If => self.fn_if(args, cell),
             Function::Iferror => self.fn_iferror(args, cell),
             Function::Ifna => self.fn_ifna(args, cell),
@@ -957,7 +957,7 @@ impl Model {
             Function::Not => self.fn_not(args, cell),
             Function::Or => self.fn_or(args, cell),
             Function::Switch => self.fn_switch(args, cell),
-            Function::True => CalcResult::Boolean(true),
+            Function::True => self.fn_true(args, cell),
             Function::Xor => self.fn_xor(args, cell),
             // Math and trigonometry
             Function::Sin => self.fn_sin(args, cell),

base/src/test/mod.rs

@@ -41,6 +41,7 @@ mod test_sheet_markup;
 mod test_sheets;
 mod test_styles;
 mod test_trigonometric;
+mod test_true_false;
 mod test_workbook;
 mod test_worksheet;
 pub(crate) mod util;

base/src/test/test_true_false.rs

@@ -0,0 +1,25 @@
+#![allow(clippy::unwrap_used)]
+
+use crate::test::util::new_empty_model;
+
+#[test]
+fn true_false_arguments() {
+    let mut model = new_empty_model();
+    model._set("A1", "=TRUE( )");
+    model._set("A2", "=FALSE( )");
+    model._set("A3", "=TRUE( 4 )");
+    model._set("A4", "=FALSE( 4 )");
+
+    model.evaluate();
+
+    assert_eq!(model._get_text("A1"), *"TRUE");
+    assert_eq!(model._get_text("A2"), *"FALSE");
+
+    assert_eq!(model._get_formula("A1"), *"=TRUE()");
+    assert_eq!(model._get_formula("A2"), *"=FALSE()");
+
+    assert_eq!(model._get_text("A3"), *"#ERROR!");
+    assert_eq!(model._get_text("A4"), *"#ERROR!");
+    assert_eq!(model._get_formula("A3"), *"=TRUE(4)");
+    assert_eq!(model._get_formula("A4"), *"=FALSE(4)");
+}