[scala][http4s] fix escaping of reserved words for correct model deserialization

Author: donilg

modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/ScalaHttp4sServerCodegen.java

@@ -16,10 +16,14 @@
 
 package org.openapitools.codegen.languages;
 
+import com.google.common.collect.ImmutableMap;
+import com.samskivert.mustache.Escapers;
+import com.samskivert.mustache.Mustache;
 import io.swagger.v3.oas.models.media.Schema;
 import org.openapitools.codegen.*;
 import org.openapitools.codegen.meta.features.*;
 import org.openapitools.codegen.model.*;
+import org.openapitools.codegen.templating.mustache.EscapeKeywordLambda;
 import org.openapitools.codegen.utils.ModelUtils;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -353,8 +357,7 @@ public Map<String, ModelsMap> postProcessAllModels(Map<String, ModelsMap> objs)
 
                 if (!cModel.oneOf.isEmpty()) {
                     cModel.getVendorExtensions().put("x-isSealedTrait", true);
-                }
-                else if (cModel.isEnum) {
+                } else if (cModel.isEnum) {
                     cModel.getVendorExtensions().put("x-isEnum", true);
 
                 } else {
@@ -557,7 +560,34 @@ public String getHelp() {
 
     @Override
     public String escapeReservedWord(String name) {
-        return "_" + name;
+        if (this.reservedWordsMappings().containsKey(name)) {
+            return this.reservedWordsMappings().get(name);
+        }
+        // Reserved words will be further escaped at the mustache compiler level.
+        // Scala escaping done here (via `, without compiler escaping) would otherwise be HTML encoded.
+        return "`" + name + "`";
+    }
+
+    @Override
+    public Mustache.Compiler processCompiler(Mustache.Compiler compiler) {
+        Mustache.Escaper SCALA = new Mustache.Escaper() {
+            @Override
+            public String escape(String text) {
+                // Fix included as suggested by akkie in #6393
+                // The given text is a reserved word which is escaped by enclosing it with grave accents. If we would
+                // escape that with the default Mustache `HTML` escaper, then the escaper would also escape our grave
+                // accents. So we remove the grave accents before the escaping and add it back after the escaping.
+                if (text.startsWith("`") && text.endsWith("`")) {
+                    String unescaped = text.substring(1, text.length() - 1);
+                    return "`" + Escapers.HTML.escape(unescaped) + "`";
+                }
+
+                // All none reserved words will be escaped with the default Mustache `HTML` escaper
+                return Escapers.HTML.escape(text);
+            }
+        };
+
+        return compiler.withEscaper(SCALA);
     }
 
     @Override
@@ -807,12 +837,12 @@ private String cpToPathParameter(CodegenParameter cp, Set<String> imports, Map<S
 
         if (_vendorExtensions.size() == 1) { // only `x-type`
             if ("String".equals(cp.getDataType())) {
-                return cp.paramName;
+                return escapeReservedWordUnapply(cp.baseName);
             } else {
-                return cp.dataType + "Varr(" + cp.paramName + ")";
+                return cp.dataType + "Varr(" + escapeReservedWordUnapply(cp.baseName) + ")";
             }
         } else {
-            return cp.baseName + "Varr(" + cp.paramName + ")";
+            return cp.baseName + "Varr(" + escapeReservedWordUnapply(cp.baseName) + ")";
         }
     }
 
@@ -844,11 +874,23 @@ private String cpToQueryParameter(CodegenParameter cp, Set<String> imports, Map<
         }
 
         vendorExtensions.putAll(refineProp(cp, imports));
-        return cp.baseName + "QueryParam(" + cp.paramName + ")";
+        return cp.baseName + "QueryParam(" + escapeReservedWordUnapply(cp.baseName) + ")";
     }
 
     @Override
     public GeneratorLanguage generatorLanguage() {
         return GeneratorLanguage.SCALA;
     }
+
+    @Override
+    protected ImmutableMap.Builder<String, Mustache.Lambda> addMustacheLambdas() {
+        return super.addMustacheLambdas()
+                .put("escapeReservedWordUnapply", new EscapeKeywordLambda(this::escapeReservedWordUnapply));
+    }
+
+    private String escapeReservedWordUnapply(String value) {
+        // The unapply method doesn’t allow you to work with reserved variables via backticks;
+        // in such cases you should use the variable via a placeholder instead.
+        return isReservedWord(value) ? "_" + value : value;
+    }
 }

modules/openapi-generator/src/main/resources/scala-http4s-server/delegateCallGeneric.mustache

@@ -1,6 +1,6 @@
 {{^authName}}
-delegate.{{operationId}}.handle(req, {{#pathParams}}{{paramName}}, {{/pathParams}}{{#queryParams}}{{paramName}}, {{/queryParams}}responses)
+delegate.{{operationId}}.handle(req, {{#pathParams}}{{#lambda.escapeReservedWordUnapply}}{{baseName}}{{/lambda.escapeReservedWordUnapply}}, {{/pathParams}}{{#queryParams}}{{#lambda.escapeReservedWordUnapply}}{{baseName}}{{/lambda.escapeReservedWordUnapply}}, {{/queryParams}}responses)
 {{/authName}}
 {{#authName}}
-delegate.{{operationId}}.handle_{{authName}}(auth, req, {{#pathParams}}{{paramName}}, {{/pathParams}}{{#queryParams}}{{paramName}}, {{/queryParams}}responses)
+delegate.{{operationId}}.handle_{{authName}}(auth, req, {{#pathParams}}{{#lambda.escapeReservedWordUnapply}}{{baseName}}{{/lambda.escapeReservedWordUnapply}}, {{/pathParams}}{{#queryParams}}{{#lambda.escapeReservedWordUnapply}}{{baseName}}{{/lambda.escapeReservedWordUnapply}}, {{/queryParams}}responses)
 {{/authName}}

modules/openapi-generator/src/main/resources/scala-http4s-server/delegateCallJson.mustache

@@ -1,6 +1,6 @@
 {{^authName}}
-  delegate.{{operationId}}.handle(req, req.asJsonDecode[{{{bodyParam.dataType}}}] , {{#pathParams}}{{paramName}}, {{/pathParams}}{{#queryParams}}{{paramName}}, {{/queryParams}}responses)
+  delegate.{{operationId}}.handle(req, req.asJsonDecode[{{{bodyParam.dataType}}}] , {{#pathParams}}{{#lambda.escapeReservedWordUnapply}}{{baseName}}{{/lambda.escapeReservedWordUnapply}}, {{/pathParams}}{{#queryParams}}{{#lambda.escapeReservedWordUnapply}}{{baseName}}{{/lambda.escapeReservedWordUnapply}}, {{/queryParams}}responses)
 {{/authName}}
 {{#authName}}
-  delegate.{{operationId}}.handle_{{authName}}(auth, req, req.asJsonDecode[{{{bodyParam.dataType}}}] , {{#pathParams}}{{paramName}}, {{/pathParams}}{{#queryParams}}{{paramName}}, {{/queryParams}}responses)
+  delegate.{{operationId}}.handle_{{authName}}(auth, req, req.asJsonDecode[{{{bodyParam.dataType}}}] , {{#pathParams}}{{#lambda.escapeReservedWordUnapply}}{{baseName}}{{/lambda.escapeReservedWordUnapply}}, {{/pathParams}}{{#queryParams}}{{#lambda.escapeReservedWordUnapply}}{{baseName}}{{/lambda.escapeReservedWordUnapply}}, {{/queryParams}}responses)
 {{/authName}}

samples/server/petstore/scala-http4s-server/src/main/scala/org/openapitools/apis/FakeApi.scala

@@ -57,8 +57,8 @@ trait FakeApiDelegate[F[_]] {
 
     def handle(
       req: Request[F],
-      _type: String,
-      _var: Option[String],
+      `type`: String,
+      `var`: Option[String],
       responses: reservedWordsResponses[F]
     ): F[Response[F]]
 

samples/server/petstore/scala-http4s-server/src/main/scala/org/openapitools/models/types.scala

@@ -15,13 +15,13 @@ import java.time.ZonedDateTime
 /**
 * Describes the result of uploading an image resource
 * @param code 
-* @param _type 
+* @param `type` 
 * @param message 
 */
 
 case class ApiResponse(
   code: Option[Int],
-  _type: Option[String],
+  `type`: Option[String],
   message: Option[String]
 )
 object ApiResponse {