Merge pull request #596 from neo4j/594-minus-with-a-single-variable

Add support for minus operator as a unary operator

Author: angrykoala

.changeset/calm-moles-yell.md

@@ -0,0 +1,10 @@
+---
+"@neo4j/cypher-builder": patch
+---
+
+Support for a single value in `Cypher.minus` operator:
+
+```js
+Cypher.minus(var1, var2); // var1 - var2
+Cypher.minus(var1); // -var1
+```

src/expressions/operations/math.test.ts

@@ -64,6 +64,18 @@ describe("math operators", () => {
         expect(cypher).toMatchInlineSnapshot(`"(10 - 3)"`);
     });
 
+    test("minus with a single parameter", () => {
+        const subtract = Cypher.minus(new Cypher.Literal(10));
+        const { cypher } = new TestClause(subtract).build();
+        expect(cypher).toMatchInlineSnapshot(`"-10"`);
+    });
+
+    test("minus with a single expression", () => {
+        const subtract = Cypher.minus(Cypher.multiply(new Cypher.Literal(10), new Cypher.Literal(2)));
+        const { cypher } = new TestClause(subtract).build();
+        expect(cypher).toMatchInlineSnapshot(`"-(10 * 2)"`);
+    });
+
     test("divide", () => {
         const divide = Cypher.divide(new Cypher.Literal(10), new Cypher.Literal(3));
         const { cypher } = new TestClause(divide).build();

src/expressions/operations/math.ts

@@ -28,8 +28,8 @@ type MathOperator = "+" | "-" | "*" | "/" | "%" | "^";
  * @category Math
  */
 export class MathOp extends CypherASTNode {
-    private readonly operator: MathOperator;
-    private readonly exprs: Expr[];
+    protected readonly operator: MathOperator;
+    protected readonly exprs: Expr[];
 
     /** @internal */
     constructor(operator: MathOperator, exprs: Expr[]) {
@@ -49,6 +49,25 @@ export class MathOp extends CypherASTNode {
     }
 }
 
+class UnaryMathOp extends MathOp {
+    constructor(operator: MathOperator, expr: Expr) {
+        super(operator, [expr]);
+    }
+
+    /**
+     * @internal
+     */
+    public getCypher(env: CypherEnvironment): string {
+        const expr = this.exprs[0];
+        if (!expr) {
+            throw new Error("Error in Cypher.minus, expr is not defined");
+        }
+        const exprStr = expr.getCypher(env);
+
+        return `${this.operator}${exprStr}`;
+    }
+}
+
 function createOp(op: MathOperator, exprs: Expr[]): MathOp {
     return new MathOp(op, exprs);
 }
@@ -65,12 +84,15 @@ export function plus(...exprs: Expr[]): MathOp {
     return createOp("+", exprs);
 }
 
-/**
+/** Minus (-) operator. This operator can be used as a mathematical operator between 2 expressions (3-2) or to negate a single expression (-1)
  * @see {@link https://neo4j.com/docs/cypher-manual/current/syntax/operators/#query-operators-mathematical | Cypher Documentation}
  * @group Operators
  * @category Math
  */
-export function minus(leftExpr: Expr, rightExpr: Expr): MathOp {
+export function minus(leftExpr: Expr, rightExpr?: Expr): MathOp {
+    if (rightExpr === undefined) {
+        return new UnaryMathOp("-", leftExpr);
+    }
     return createOp("-", [leftExpr, rightExpr]);
 }