C++ string constants as std::string_view

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

CHANGELOG.md

@@ -1,6 +1,8 @@
 # Gluecodium project Release Notes
 
 ## Unreleased
+### Features:
+  * Constants of `String` type are now generated as `std::string_view` in C++ code.
 ### Breaking changes:
   * The `gluecodium::optional` type alias to `std::optional` was removed from C++ generated code.
 

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

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

@@ -10,6 +10,5 @@ const int32_t Constants::INT_CONSTANT = -11;
 const uint32_t Constants::UINT_CONSTANT = 4294967295;
 const float Constants::FLOAT_CONSTANT = 2.71f;
 const double Constants::DOUBLE_CONSTANT = -3.14;
-const ::std::string Constants::STRING_CONSTANT = "Foo bar";
 const ::smoke::Constants::StateEnum Constants::ENUM_CONSTANT = ::smoke::Constants::StateEnum::ON;
 }

gluecodium/src/test/resources/smoke/structs/output/cpp/include/smoke/StructsWithConstants.h

@@ -6,10 +6,11 @@
 #include "gluecodium/ExportGluecodiumCpp.h"
 #include "smoke/RouteUtils.h"
 #include <string>
+#include <string_view>
 namespace smoke {
 struct _GLUECODIUM_CPP_EXPORT StructsWithConstants {
     struct _GLUECODIUM_CPP_EXPORT Route {
-        static const ::std::string DEFAULT_DESCRIPTION;
+        static constexpr std::string_view DEFAULT_DESCRIPTION = "Nonsense";
         static const ::smoke::RouteUtils::RouteType DEFAULT_TYPE;
         ::std::string description;
         ::smoke::RouteUtils::RouteType type;

gluecodium/src/test/resources/smoke/structs/output/cpp/include/smoke/StructsWithConstantsInterface.h

@@ -7,6 +7,7 @@
 #include "gluecodium/VectorHash.h"
 #include "smoke/RouteUtils.h"
 #include <string>
+#include <string_view>
 #include <vector>
 namespace smoke {
 class _GLUECODIUM_CPP_EXPORT StructsWithConstantsInterface {
@@ -15,15 +16,15 @@ class _GLUECODIUM_CPP_EXPORT StructsWithConstantsInterface {
     virtual ~StructsWithConstantsInterface() = 0;
 public:
     struct _GLUECODIUM_CPP_EXPORT MultiRoute {
-        static const ::std::string DEFAULT_DESCRIPTION;
+        static constexpr std::string_view DEFAULT_DESCRIPTION = "Foo";
         static const ::smoke::RouteUtils::RouteType DEFAULT_TYPE;
         ::std::vector< ::std::string > descriptions;
         ::smoke::RouteUtils::RouteType type;
         MultiRoute( );
         MultiRoute( ::std::vector< ::std::string > descriptions, ::smoke::RouteUtils::RouteType type );
     };
     struct _GLUECODIUM_CPP_EXPORT StructWithConstantsOnly {
-        static const ::std::string DEFAULT_DESCRIPTION;
+        static constexpr std::string_view DEFAULT_DESCRIPTION = "Foo";
     };
 };
 }

gluecodium/src/test/resources/smoke/structs/output/cpp/src/smoke/StructsWithConstants.cpp

@@ -5,7 +5,6 @@
 #include "smoke/StructsWithConstants.h"
 #include <utility>
 namespace smoke {
-const ::std::string StructsWithConstants::Route::DEFAULT_DESCRIPTION = "Nonsense";
 const ::smoke::RouteUtils::RouteType StructsWithConstants::Route::DEFAULT_TYPE = ::smoke::RouteUtils::RouteType::EQUESTRIAN;
 StructsWithConstants::Route::Route( )
     : description{ }, type{ }

gluecodium/src/test/resources/smoke/structs/output/cpp/src/smoke/StructsWithConstantsInterface.cpp

@@ -9,7 +9,6 @@ StructsWithConstantsInterface::StructsWithConstantsInterface() {
 }
 StructsWithConstantsInterface::~StructsWithConstantsInterface() {
 }
-const ::std::string StructsWithConstantsInterface::MultiRoute::DEFAULT_DESCRIPTION = "Foo";
 const ::smoke::RouteUtils::RouteType StructsWithConstantsInterface::MultiRoute::DEFAULT_TYPE = ::smoke::RouteUtils::RouteType::NONE;
 StructsWithConstantsInterface::MultiRoute::MultiRoute( )
     : descriptions{ }, type{ }
@@ -19,5 +18,4 @@ StructsWithConstantsInterface::MultiRoute::MultiRoute( ::std::vector< ::std::str
     : descriptions( std::move( descriptions ) ), type( std::move( type ) )
 {
 }
-const ::std::string StructsWithConstantsInterface::StructWithConstantsOnly::DEFAULT_DESCRIPTION = "Foo";
 }