Try propagating placeholder values using existing code generators

Author: yevhenii-nadtochii

java/src/main/kotlin/io/spine/validation/java/CodeGenerator.kt

@@ -32,7 +32,6 @@ import com.squareup.javapoet.CodeBlock
 import io.spine.logging.WithLogging
 import io.spine.protodata.java.Expression
 import io.spine.tools.java.codeBlock
-import io.spine.validation.ErrorMessage
 import io.spine.validation.Rule.KindCase.COMPOSITE
 import io.spine.validation.Rule.KindCase.MESSAGE_WIDE
 import io.spine.validation.Rule.KindCase.SIMPLE
@@ -98,7 +97,7 @@ internal abstract class CodeGenerator(
     /**
      * Forms an error message for the found violation.
      */
-    abstract fun error(): ErrorMessage
+    abstract fun error(): Pair<String, Map<Expression<*>, Expression<*>>>
 
     /**
      * Constructs code which creates a `ConstrainViolation` and puts it into a list of violations.

java/src/main/kotlin/io/spine/validation/java/DistributingGenerator.kt

@@ -47,7 +47,6 @@ import io.spine.string.titleCase
 import io.spine.tools.java.codeBlock
 import io.spine.tools.java.methodSpec
 import io.spine.validate.ConstraintViolation
-import io.spine.validation.ErrorMessage
 import javax.lang.model.element.Modifier
 
 /**
@@ -146,7 +145,7 @@ internal class DistributingGenerator(
         return MethodCall(violationsName, "isEmpty")
     }
 
-    override fun error(): ErrorMessage =
+    override fun error(): Pair<String, Map<Expression<*>, Expression<*>>> =
         delegate.error()
 
     override fun createViolation(): CodeBlock = codeBlock {

java/src/main/kotlin/io/spine/validation/java/ErrorMessages.kt

@@ -41,6 +41,7 @@ import io.spine.protodata.java.call
 import io.spine.protodata.java.newBuilder
 import io.spine.protodata.ast.isList
 import io.spine.protodata.ast.isMap
+import io.spine.protodata.java.mapExpression
 import io.spine.protodata.java.packToAny
 import io.spine.validate.ConstraintViolation
 import io.spine.validate.TemplateString
@@ -88,7 +89,7 @@ public fun ErrorMessage.createCompositeViolation(
     return addViolation(violation, violationsList)
 }
 
-private fun addViolation(
+public fun addViolation(
     violation: Expression<ConstraintViolation>,
     violationsList: Expression<MutableList<ConstraintViolation>>
 ): CodeBlock = CodeBlock.builder()
@@ -100,9 +101,19 @@ private fun ErrorMessage.buildViolation(
     field: Field?,
     fieldValue: Expression<*>?,
     ignoreCardinality: Boolean = false
+) = buildViolation(this.toString(), type, field, fieldValue, ignoreCardinality)
+
+public fun buildViolation(
+    errorMessage: String,
+    type: TypeName,
+    field: Field?,
+    fieldValue: Expression<*>?,
+    ignoreCardinality: Boolean = false,
+    placeholders: Map<Expression<*>, Expression<*>> = emptyMap() // TODO: Fix in ProtoData.
 ): Expression<ConstraintViolation> {
     val message = ClassName(TemplateString::class).newBuilder()
-        .chainSet("withPlaceholders", Literal(this))
+        .chainSet("withPlaceholders", Literal(errorMessage))
+        .chainPutAll("placeholderValue", mapExpression(ClassName(String::class), ClassName(String::class), placeholders))
         .chainBuild<TemplateString>()
     var violationBuilder = ClassName(ConstraintViolation::class).newBuilder()
         .chainSet("message", message)

java/src/main/kotlin/io/spine/validation/java/RequiredOneofGenerator.kt

@@ -26,11 +26,11 @@
 
 package io.spine.validation.java
 
+import com.squareup.javapoet.CodeBlock
 import io.spine.protodata.ast.Cardinality.CARDINALITY_SINGLE
 import io.spine.protodata.ast.OneofName
 import io.spine.protodata.java.Expression
 import io.spine.protodata.java.field
-import io.spine.validation.ErrorMessage
 
 /**
  * A code generator for the `(is_required)` constraint.
@@ -54,9 +54,18 @@ internal class RequiredOneofGenerator(
         return Expression("$numberGetter != 0")
     }
 
-    override fun error() =
-        ErrorMessage.forRule(rule.errorMessage)
+    override fun error() = rule.errorMessage to emptyMap<Expression<*>, Expression<*>>()
 
-    override fun createViolation() =
-        error().createViolation(ctx)
+    override fun createViolation(): CodeBlock {
+        val error = error()
+        val violation = buildViolation(
+            error.first,
+            ctx.validatedType,
+            ctx.fieldFromSimpleRule,
+            ctx.fieldOrElement,
+            ignoreCardinality = ctx.isElement,
+            error.second
+        )
+        return addViolation(violation, ctx.violationList)
+    }
 }

java/src/main/kotlin/io/spine/validation/java/SimpleRuleGenerator.kt

@@ -33,8 +33,11 @@ import io.spine.protodata.ast.PrimitiveType.TYPE_STRING
 import io.spine.protodata.ast.Type
 import io.spine.protodata.ast.isList
 import io.spine.protodata.ast.isMap
+import io.spine.protodata.ast.qualifiedName
+import io.spine.protodata.ast.typeName
 import io.spine.protodata.java.ClassName
 import io.spine.protodata.java.Expression
+import io.spine.protodata.java.StringLiteral
 import io.spine.protodata.java.call
 import io.spine.protodata.value.Value
 import io.spine.string.shortly
@@ -45,7 +48,6 @@ import io.spine.validation.ComparisonOperator.GREATER_THAN
 import io.spine.validation.ComparisonOperator.LESS_OR_EQUAL
 import io.spine.validation.ComparisonOperator.LESS_THAN
 import io.spine.validation.ComparisonOperator.NOT_EQUAL
-import io.spine.validation.ErrorMessage
 import io.spine.validation.SimpleRule
 import io.spine.validation.SimpleRule.OperatorKindCase.CUSTOM_OPERATOR
 import io.spine.validation.SimpleRule.OperatorKindCase.OPERATOR
@@ -142,18 +144,32 @@ internal open class SimpleRuleGenerator(ctx: GenerationContext) : CodeGenerator(
         PRIMITIVE_COMPARISON_OPS
     }
 
-    override fun error(): ErrorMessage {
-        val actualValue = ClassName(String::class)
+    override fun error(): Pair<String, Map<Expression<*>, Expression<*>>> {
+        val fieldValue = ClassName(String::class)
             .call<String>("valueOf", ctx.fieldOrElement!!)
-        return ErrorMessage.forRule(
-            rule.errorMessage,
-            actualValue.toCode(),
-            otherValue?.toCode()
+        val fieldPath = rule.field.value
+        val fieldType = ctx.simpleRuleField.type.typeName.qualifiedName
+        val parentType = ctx.validatedType.qualifiedName
+        return rule.errorMessage to mapOf(
+            StringLiteral("field.path") to StringLiteral(fieldPath),
+            StringLiteral("parent.type") to StringLiteral(parentType),
+            StringLiteral("field.type") to StringLiteral(fieldType),
+            StringLiteral("field.value") to fieldValue
         )
     }
 
-    override fun createViolation(): CodeBlock =
-        error().createViolation(ctx)
+    override fun createViolation(): CodeBlock {
+        val error = error()
+        val violation = buildViolation(
+            error.first,
+            ctx.validatedType,
+            ctx.fieldFromSimpleRule,
+            ctx.fieldOrElement,
+            ignoreCardinality = ctx.isElement,
+            error.second
+        )
+        return addViolation(violation, ctx.violationList)
+    }
 }
 
 internal fun generatorForSimple(ctx: GenerationContext): CodeGenerator {