Merge pull request #35 from hasura/build-comparison-cleanup

cleaned up comparison handling around IN operator

Author: gneeri

ndc-sqlgen/src/main/kotlin/io/hasura/ndc/sqlgen/BaseGenerator.kt

@@ -28,18 +28,26 @@ sealed interface BaseGenerator {
     fun buildComparison(
         col: Field<Any>,
         operator: ApplyBinaryComparisonOperator,
-        value: Field<Any>
+        listVal: List<Field<Any>>
     ): Condition {
+        if (operator != ApplyBinaryComparisonOperator.IN && listVal.size != 1) {
+            error("Only the IN operator supports multiple values")
+        }
+
+        // unwrap single value for use in all but the IN operator
+        // OR return falseCondition if listVal is empty
+        val singleVal = listVal.firstOrNull() ?: return DSL.falseCondition()
+
         return when (operator) {
-            ApplyBinaryComparisonOperator.EQ -> col.eq(value)
-            ApplyBinaryComparisonOperator.GT -> col.gt(value)
-            ApplyBinaryComparisonOperator.GTE -> col.ge(value)
-            ApplyBinaryComparisonOperator.LT -> col.lt(value)
-            ApplyBinaryComparisonOperator.LTE -> col.le(value)
-            ApplyBinaryComparisonOperator.IN -> DSL.nullCondition()
+            ApplyBinaryComparisonOperator.EQ -> col.eq(singleVal)
+            ApplyBinaryComparisonOperator.GT -> col.gt(singleVal)
+            ApplyBinaryComparisonOperator.GTE -> col.ge(singleVal)
+            ApplyBinaryComparisonOperator.LT -> col.lt(singleVal)
+            ApplyBinaryComparisonOperator.LTE -> col.le(singleVal)
+            ApplyBinaryComparisonOperator.IN -> col.`in`(listVal)
             ApplyBinaryComparisonOperator.IS_NULL -> col.isNull
-            ApplyBinaryComparisonOperator.LIKE -> col.like(value as Field<String>)
-            ApplyBinaryComparisonOperator.CONTAINS -> col.contains(value as Field<String>)
+            ApplyBinaryComparisonOperator.LIKE -> col.like(singleVal as Field<String>)
+            ApplyBinaryComparisonOperator.CONTAINS -> col.contains(singleVal as Field<String>)
         }
     }
 
@@ -124,15 +132,16 @@ sealed interface BaseGenerator {
                 val comparisonValue = when (val v = e.value) {
                     is ComparisonValue.ColumnComp -> {
                         val col = splitCollectionName(getCollectionForCompCol(v.column, request))
-                        DSL.field(DSL.name(col + v.column.name))
+                        listOf(DSL.field(DSL.name(col + v.column.name)))
                     }
 
                     is ComparisonValue.ScalarComp ->
-                        if(e.operator == ApplyBinaryComparisonOperator.IN)
-                            return handleInComp(column, v)
-                         else DSL.inline(v.value)
+                        when (val scalarValue = v.value) {
+                            is List<*> -> (scalarValue as List<Any>).map { DSL.inline(it) }
+                            else -> listOf(DSL.inline(scalarValue))
+                        }
 
-                    is ComparisonValue.VariableComp -> DSL.field(DSL.name(listOf("vars", v.name)))
+                    is ComparisonValue.VariableComp -> listOf(DSL.field(DSL.name(listOf("vars", v.name))))
                 }
                 return buildComparison(column, e.operator, comparisonValue)
             }
@@ -212,17 +221,6 @@ sealed interface BaseGenerator {
         }
     }
 
-    fun handleInComp(column: Field<Any>, value: ComparisonValue.ScalarComp): Condition {
-        return when (val scalarValue = value.value) {
-            is List<*> -> {
-                if (scalarValue.isEmpty()) DSL.falseCondition()
-                else column.`in`(scalarValue.map { DSL.inline(it) })
-            }
-            // Handle non-array scalar value
-            else -> column.eq(DSL.inline(scalarValue))
-        }
-    }
-
     fun splitCollectionName(collectionName: String): List<String> {
         return collectionName.split(".")
     }