C++ string constants as std::string_view

Resolves: #203
Signed-off-by: Daniel Kamkha <[email protected]>

Author: DanielKamkha

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Gluecodium project Release Notes
 
+## Unreleased
+### Features:
+  * Constants of `String` type are now generated as `std::string_view` in C++ code.
+
 ## 13.4.0
 Release date: 2022-08-29
 ### Features:

functional-tests/functional/input/src/cpp/Constants.cpp

@@ -53,7 +53,7 @@ UseTypeCollectionConstants::get_double_constant( )
 std::string
 UseTypeCollectionConstants::get_string_constant( )
 {
-    return test::Constants::STRING_CONSTANT;
+    return std::string{test::Constants::STRING_CONSTANT};
 }
 
 test::Constants::StateEnum
@@ -91,7 +91,7 @@ UseInterfaceConstants::get_double_constant( )
 std::string
 UseInterfaceConstants::get_string_constant( )
 {
-    return ConstantsInterface::STRING_CONSTANT;
+    return std::string{ConstantsInterface::STRING_CONSTANT};
 }
 
 ConstantsInterface::StateEnum

functional-tests/functional/input/src/cpp/StructsWithConstants.cpp

@@ -27,13 +27,13 @@ namespace test
 std::string
 SimpleRoute::get_default_description( )
 {
-    return SimpleRoute::DEFAULT_DESCRIPTION;
+    return std::string{SimpleRoute::DEFAULT_DESCRIPTION};
 }
 
 std::string
 StructsWithConstantsInterface::MultiRoute::get_default_description( )
 {
-    return StructsWithConstantsInterface::MultiRoute::DEFAULT_DESCRIPTION;
+    return std::string{StructsWithConstantsInterface::MultiRoute::DEFAULT_DESCRIPTION};
 }
 
 }

gluecodium/src/main/java/com/here/gluecodium/generator/cpp/CppGeneratorPredicates.kt

@@ -23,6 +23,7 @@ import com.here.gluecodium.generator.common.CommonGeneratorPredicates
 import com.here.gluecodium.model.lime.LimeAttributeType
 import com.here.gluecodium.model.lime.LimeAttributeValueType
 import com.here.gluecodium.model.lime.LimeBasicType
+import com.here.gluecodium.model.lime.LimeConstant
 import com.here.gluecodium.model.lime.LimeContainerWithInheritance
 import com.here.gluecodium.model.lime.LimeField
 import com.here.gluecodium.model.lime.LimeFunction
@@ -82,6 +83,7 @@ internal object CppGeneratorPredicates {
                     it.attributes.have(LimeAttributeType.CPP, LimeAttributeValueType.CSTRING)
             }
         },
+        "isStringConstant" to { limeConstant: Any -> limeConstant is LimeConstant && isStringConstant(limeConstant) },
         "needsAllFieldsConstructor" to { limeStruct: Any ->
             when {
                 limeStruct !is LimeStruct -> false
@@ -112,6 +114,11 @@ internal object CppGeneratorPredicates {
         }
     )
 
+    fun isStringConstant(limeConstant: LimeConstant): Boolean {
+        val actualType = limeConstant.typeRef.type.actualType
+        return actualType is LimeBasicType && actualType.typeId == LimeBasicType.TypeId.STRING
+    }
+
     private fun needsNotNullComment(limeTypeRef: LimeTypeRef) =
         !limeTypeRef.isNullable && limeTypeRef.type.actualType is LimeContainerWithInheritance
 

gluecodium/src/main/java/com/here/gluecodium/generator/cpp/CppHeaderIncludesCollector.kt

@@ -48,9 +48,8 @@ internal class CppHeaderIncludesCollector(
         val allValues = LimeTypeHelper.getAllValues(limeElement)
         val equatableTypes =
             allTypes.filter { it.external?.cpp == null && it.attributes.have(LimeAttributeType.EQUATABLE) }
-        return allTypes.filterIsInstance<LimeContainer>()
-            .flatMap { it.functions }
-            .flatMap { includesResolver.resolveElementImports(it) } +
+        val containers = allTypes.filterIsInstance<LimeContainer>()
+        return containers.flatMap { it.functions }.flatMap { includesResolver.resolveElementImports(it) } +
             allTypeRefs.flatMap { includesResolver.resolveElementImports(it) } +
             allValues.flatMap { includesResolver.resolveElementImports(it) } +
             allTypes.flatMap { includesResolver.resolveElementImports(it) } +
@@ -82,6 +81,9 @@ internal class CppHeaderIncludesCollector(
         if (typeRegisteredClasses.isNotEmpty()) {
             additionalIncludes += includesResolver.typeRepositoryInclude
         }
+        if (limeElement is LimeContainer && limeElement.constants.any { CppGeneratorPredicates.isStringConstant(it) }) {
+            additionalIncludes += CppLibraryIncludes.STRING_VIEW
+        }
         return additionalIncludes
     }
 }

gluecodium/src/main/resources/templates/cpp/CppClassImpl.mustache

@@ -45,7 +45,7 @@ bool
 {{>cpp/CppStructImpl}}
 {{/structs}}
 {{#constants}}
-const {{resolveName typeRef}} {{parentName}}::{{resolveName}} = {{resolveName value}};
+{{>cpp/CppConstantImpl}}
 {{/constants}}
 {{#each classes interfaces}}
 {{>cpp/CppClassImpl}}

gluecodium/src/main/resources/templates/cpp/CppConstant.mustache

@@ -19,4 +19,6 @@
   !
   !}}
 {{>cpp/CppDocComment}}{{>cpp/CppAttributes}}
-{{#if needsExport}}{{>cpp/CppExportMacro}}{{/if}}{{storageQualifier}} const {{resolveName typeRef}} {{resolveName}};
+{{#if needsExport}}{{>cpp/CppExportMacro}}{{/if}}{{storageQualifier}} {{!!
+}}{{#ifPredicate "isStringConstant"}}constexpr std::string_view {{resolveName}} = {{resolveName value}}{{/ifPredicate}}{{!!
+}}{{#unlessPredicate "isStringConstant"}}const {{resolveName typeRef}} {{resolveName}}{{/unlessPredicate}};

gluecodium/src/main/resources/templates/cpp/CppConstantImpl.mustache

@@ -0,0 +1,22 @@
+{{!!
+  !
+  ! Copyright (C) 2016-2022 HERE Europe B.V.
+  !
+  ! Licensed under the Apache License, Version 2.0 (the "License");
+  ! you may not use this file except in compliance with the License.
+  ! You may obtain a copy of the License at
+  !
+  !     http://www.apache.org/licenses/LICENSE-2.0
+  !
+  ! Unless required by applicable law or agreed to in writing, software
+  ! distributed under the License is distributed on an "AS IS" BASIS,
+  ! WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  ! See the License for the specific language governing permissions and
+  ! limitations under the License.
+  !
+  ! SPDX-License-Identifier: Apache-2.0
+  ! License-Filename: LICENSE
+  !
+  !}}
+{{#unlessPredicate "isStringConstant"}}const {{resolveName typeRef}} {{parentName}}::{{resolveName}} = {{resolveName value}};
+{{/unlessPredicate}}

gluecodium/src/main/resources/templates/cpp/CppStructImpl.mustache

@@ -27,7 +27,7 @@
 {{>cpp/CppStructImpl}}
 {{/structs}}
 {{#constants}}
-const {{resolveName typeRef}} {{parentName}}::{{resolveName}} = {{resolveName value}};
+{{>cpp/CppConstantImpl}}
 {{/constants}}
 {{#each classes interfaces}}
 {{>cpp/CppClassImpl}}

gluecodium/src/test/resources/smoke/constants/output/cpp/include/smoke/Constants.h

@@ -6,14 +6,15 @@
 #include "gluecodium/ExportGluecodiumCpp.h"
 #include <cstdint>
 #include <string>
+#include <string_view>
 namespace smoke {
 struct _GLUECODIUM_CPP_EXPORT Constants {
     static const bool BOOL_CONSTANT;
     static const int32_t INT_CONSTANT;
     static const uint32_t UINT_CONSTANT;
     static const float FLOAT_CONSTANT;
     static const double DOUBLE_CONSTANT;
-    static const ::std::string STRING_CONSTANT;
+    static constexpr std::string_view STRING_CONSTANT = "Foo bar";
     enum class StateEnum {
         OFF,
         ON