fix: Try not to fail when comparing different types [DHIS2-21115]

build.gradle.kts

@@ -9,7 +9,7 @@ repositories {
     mavenCentral()
 }
 
-version = "1.3.1-SNAPSHOT"
+version = "1.4.0-SNAPSHOT"
 group = "org.hisp.dhis.lib.expression"
 
 if (project.hasProperty("removeSnapshotSuffix")) {

src/commonMain/kotlin/org/hisp/dhis/lib/expression/ast/BinaryOperator.kt

@@ -201,16 +201,19 @@ enum class BinaryOperator(val symbol: String, private val returnType: ValueType,
             if (left == null || right == null) {
                 return left == null && right == null
             }
-            if (left is Boolean || right is Boolean) {
-                return Typed.toBooleanTypeCoercion(left) == Typed.toBooleanTypeCoercion(right)
+            if (left is Number || right is Number) {
+                val leftNum = tryToNumber(left) ?: return false
+                val rightNum = tryToNumber(right) ?: return false
+                return leftNum == rightNum
             }
-            return if (left is Number || right is Number) {
-                Typed.toNumberTypeCoercion(left) == Typed.toNumberTypeCoercion(
-                    right
-                )
+            return if (left is Boolean || right is Boolean) {
+                Typed.toBooleanTypeCoercion(left) == Typed.toBooleanTypeCoercion(right)
             } else left == right
         }
 
+        private fun tryToNumber(value: Any?): Double? {
+            return try { Typed.toNumberTypeCoercion(value) } catch (_: Exception) { null }
+        }
 
         fun notEqual(left: Any?, right: Any?): Boolean {
             return !equal(left, right)

src/commonTest/kotlin/org/hisp/dhis/lib/expression/operator/CompareExpressionTest.kt

@@ -87,19 +87,35 @@ internal class CompareExpressionTest {
         assertEquals(true, evaluate("'hi' == \"hi\""))
         assertEquals(true, evaluate("'true' == true"))
         assertEquals(true, evaluate("true == 'true'"))
+
+        // Any value that cannot be coerced to a number is not equal to any number
+        assertEquals(false, evaluate("2 == ''"))
+        assertEquals(false, evaluate("2 == 'any string that is not a number'"))
+
+        // Booleans are coerced to numbers (true→1, false→0) when compared with a number
+        assertEquals(true, evaluate("1 == true"))
+        assertEquals(true, evaluate("0 == false"))
+        assertEquals(false, evaluate("0 == true"))
+        assertEquals(false, evaluate("1 == false"))
+        assertEquals(true, evaluate("1.0 == true"))
+        assertEquals(true, evaluate("0.0 == false"))
+        assertEquals(false, evaluate("2.5 == true"))
+        assertEquals(false, evaluate("2.5 == false"))
+        assertEquals(false, evaluate("2 == true"))
+        assertEquals(false, evaluate("2 == false"))
+
+        // Any string other than 'true' is coerced to false
+        assertEquals(true, evaluate("false == ''"))
+        assertEquals(true, evaluate("false == 'any string that is not a boolean'"))
+        assertEquals(false, evaluate("true == ''"))
+        assertEquals(false, evaluate("true == 'any string that is not a boolean'"))
     }
 
     @Test
     fun testDivideByZero() {
         assertEquals(false, evaluate("2 == 2 / 0"))
     }
 
-    @Test
-    fun testIncompatibleTypes() {
-        val ex = assertFailsWith(IllegalArgumentException::class) { evaluate("2.1 == false") }
-        assertEquals("Could not coerce Double '2.1' to Boolean", ex.message)
-    }
-
     companion object {
         private fun evaluate(expression: String): Any? {
             return Expression(expression).evaluate()