Decouple ItemReader and ItemReaderASTVisitor.

Change-Id: I67191f686a3fdbc27186422c3ba3bd9f1f1b9c0c
Reviewed-by: Joerg Bornemann <joerg.bornemann@theqtcompany.com>

8 files changed, 293 insertions, 181 deletions

diff --git a/src/lib/corelib/corelib.qbs b/src/lib/corelib/corelib.qbs
index d0b42354b..ead8c5f5a 100644
--- a/src/lib/corelib/corelib.qbs
+++ b/src/lib/corelib/corelib.qbs
@@ -230,6 +230,8 @@ QbsLibrary {
             "itemreader.h",
             "itemreaderastvisitor.cpp",
             "itemreaderastvisitor.h",
+            "itemreadervisitorstate.cpp",
+            "itemreadervisitorstate.h",
             "jsimports.h",
             "language.cpp",
             "language.h",
diff --git a/src/lib/corelib/language/itemreader.cpp b/src/lib/corelib/language/itemreader.cpp
index 4b1f970cc..de3e78eca 100644
--- a/src/lib/corelib/language/itemreader.cpp
+++ b/src/lib/corelib/language/itemreader.cpp
@@ -29,80 +29,19 @@
 ****************************************************************************/
 
 #include "itemreader.h"
-#include "asttools.h"
-#include "itemreaderastvisitor.h"
-#include <logging/translator.h>
-#include <parser/qmljsengine_p.h>
-#include <parser/qmljslexer_p.h>
-#include <parser/qmljsparser_p.h>
-#include <tools/error.h>
-#include <QExplicitlySharedDataPointer>
-#include <QFile>
-#include <QFileInfo>
-#include <QSharedData>
-#include <QTextStream>
+
+#include "itemreadervisitorstate.h"
 
 namespace qbs {
 namespace Internal {
 
-class ASTCacheValueData : public QSharedData
-{
-    Q_DISABLE_COPY(ASTCacheValueData)
-public:
-    ASTCacheValueData()
-        : ast(0)
-        , processing(false)
-    {
-    }
-
-    QString code;
-    QbsQmlJS::Engine engine;
-    QbsQmlJS::AST::UiProgram *ast;
-    bool processing;
-};
-
-class ASTCacheValue
-{
-public:
-    ASTCacheValue()
-        : d(new ASTCacheValueData)
-    {
-    }
-
-    ASTCacheValue(const ASTCacheValue &other)
-        : d(other.d)
-    {
-    }
-
-    void setProcessingFlag(bool b) { d->processing = b; }
-    bool isProcessing() const { return d->processing; }
-
-    void setCode(const QString &code) { d->code = code; }
-    QString code() const { return d->code; }
-
-    QbsQmlJS::Engine *engine() const { return &d->engine; }
-
-    void setAst(QbsQmlJS::AST::UiProgram *ast) { d->ast = ast; }
-    QbsQmlJS::AST::UiProgram *ast() const { return d->ast; }
-    bool isValid() const { return d->ast; }
-
-private:
-    QExplicitlySharedDataPointer<ASTCacheValueData> d;
-};
-
-class ItemReader::ASTCache : public QHash<QString, ASTCacheValue> {};
-
-
-ItemReader::ItemReader(const Logger &logger)
-    : m_pool(0)
-    , m_logger(logger)
-    , m_astCache(new ASTCache)
+ItemReader::ItemReader(const Logger &logger) : m_visitorState(new ItemReaderVisitorState(logger))
 {
 }
 
 ItemReader::~ItemReader()
 {
-    delete m_astCache;
+    delete m_visitorState;
 }
 
 void ItemReader::setSearchPaths(const QStringList &searchPaths)
@@ -134,70 +73,14 @@ QStringList ItemReader::searchPaths() const
     return paths;
 }
 
-void ItemReader::cacheDirectoryEntries(const QString &dirPath, const QStringList &entries)
-{
-    m_directoryEntries.insert(dirPath, entries);
-}
-
-bool ItemReader::findDirectoryEntries(const QString &dirPath, QStringList *entries) const
-{
-    const QHash<QString, QStringList>::ConstIterator it = m_directoryEntries.constFind(dirPath);
-    if (it == m_directoryEntries.constEnd())
-        return false;
-    *entries = it.value();
-    return true;
-}
-
 Item *ItemReader::readFile(const QString &filePath)
 {
-    return internalReadFile(filePath).rootItem;
+    return m_visitorState->readFile(filePath, searchPaths(), m_pool);
 }
 
 QSet<QString> ItemReader::filesRead() const
 {
-    return m_filesRead;
-}
-
-ItemReaderResult ItemReader::internalReadFile(const QString &filePath)
-{
-    ASTCacheValue &cacheValue = (*m_astCache)[filePath];
-    if (cacheValue.isValid()) {
-        if (Q_UNLIKELY(cacheValue.isProcessing()))
-            throw ErrorInfo(Tr::tr("Loop detected when importing '%1'.").arg(filePath));
-    } else {
-        QFile file(filePath);
-        if (Q_UNLIKELY(!file.open(QFile::ReadOnly)))
-            throw ErrorInfo(Tr::tr("Cannot open '%1'.").arg(filePath));
-
-        m_filesRead.insert(filePath);
-        const QString code = QTextStream(&file).readAll();
-        QbsQmlJS::Lexer lexer(cacheValue.engine());
-        lexer.setCode(code, 1);
-        QbsQmlJS::Parser parser(cacheValue.engine());
-
-        file.close();
-        if (!parser.parse()) {
-            QList<QbsQmlJS::DiagnosticMessage> parserMessages = parser.diagnosticMessages();
-            if (Q_UNLIKELY(!parserMessages.isEmpty())) {
-                ErrorInfo err;
-                foreach (const QbsQmlJS::DiagnosticMessage &msg, parserMessages)
-                    err.append(msg.message, toCodeLocation(filePath, msg.loc));
-                throw err;
-            }
-        }
-
-        cacheValue.setCode(code);
-        cacheValue.setAst(parser.ast());
-    }
-
-    ItemReaderResult result;
-    ItemReaderASTVisitor itemReader(this, &result);
-    itemReader.setFilePath(QFileInfo(filePath).absoluteFilePath());
-    itemReader.setSourceCode(cacheValue.code());
-    cacheValue.setProcessingFlag(true);
-    cacheValue.ast()->accept(&itemReader);
-    cacheValue.setProcessingFlag(false);
-    return result;
+    return m_visitorState->filesRead();
 }
 
 } // namespace Internal
diff --git a/src/lib/corelib/language/itemreader.h b/src/lib/corelib/language/itemreader.h
index 31963ee8b..b77c16b82 100644
--- a/src/lib/corelib/language/itemreader.h
+++ b/src/lib/corelib/language/itemreader.h
@@ -34,7 +34,6 @@
 #include "forward_decls.h"
 #include <logging/logger.h>
 
-#include <QHash>
 #include <QSet>
 #include <QStack>
 #include <QStringList>
@@ -44,15 +43,7 @@ namespace Internal {
 
 class Item;
 class ItemPool;
-
-struct ItemReaderResult
-{
-    ItemReaderResult()
-        : rootItem(0)
-    {}
-
-    Item *rootItem;
-};
+class ItemReaderVisitorState;
 
 /*
  * Reads a qbs file and creates a tree of Item objects.
@@ -65,13 +56,10 @@ struct ItemReaderResult
  */
 class ItemReader
 {
-    friend class ItemReaderASTVisitor;
 public:
     ItemReader(const Logger &logger);
     ~ItemReader();
 
-    Logger logger() const { return m_logger; }
-
     void setPool(ItemPool *pool) { m_pool = pool; }
     void setSearchPaths(const QStringList &searchPaths);
     void pushExtraSearchPaths(const QStringList &extraSearchPaths);
@@ -86,21 +74,10 @@ public:
     QSet<QString> filesRead() const;
 
 private:
-    ItemReaderResult internalReadFile(const QString &filePath);
-
-    void cacheDirectoryEntries(const QString &dirPath, const QStringList &entries);
-    bool findDirectoryEntries(const QString &dirPath, QStringList *entries) const;
-
-    ItemPool *m_pool;
-    Logger m_logger;
+    ItemPool *m_pool = nullptr;
     QStringList m_searchPaths;
     QStack<QStringList> m_extraSearchPaths;
-    QHash<const Item *, QSet<JSSourceValuePtr> > m_conditionalValuesPerScopeItem;
-
-    class ASTCache;
-    ASTCache *m_astCache;
-    QSet<QString> m_filesRead;
-    QHash<QString, QStringList> m_directoryEntries;
+    ItemReaderVisitorState * const m_visitorState;
 };
 
 } // namespace Internal
diff --git a/src/lib/corelib/language/itemreaderastvisitor.cpp b/src/lib/corelib/language/itemreaderastvisitor.cpp
index b949bde1e..cf4686578 100644
--- a/src/lib/corelib/language/itemreaderastvisitor.cpp
+++ b/src/lib/corelib/language/itemreaderastvisitor.cpp
@@ -29,10 +29,12 @@
 ****************************************************************************/
 
 #include "itemreaderastvisitor.h"
+
 #include "asttools.h"
 #include "builtindeclarations.h"
 #include "identifiersearch.h"
-#include "itemreader.h"
+#include "itemreadervisitorstate.h"
+
 #include <jsextensions/jsextensions.h>
 #include <parser/qmljsast_p.h>
 #include <tools/error.h>
@@ -43,19 +45,19 @@
 
 #include <QDirIterator>
 #include <QFileInfo>
-#include <QStringList>
 
 using namespace QbsQmlJS;
 
 namespace qbs {
 namespace Internal {
 
-ItemReaderASTVisitor::ItemReaderASTVisitor(ItemReader *reader, ItemReaderResult *result)
-    : m_reader(reader)
-    , m_readerResult(result)
+ItemReaderASTVisitor::ItemReaderASTVisitor(ItemReaderVisitorState &visitorState,
+        ItemPool *itemPool, Logger logger, const QStringList &searchPaths)
+    : m_visitorState(visitorState)
     , m_file(FileContext::create())
-    , m_item(0)
-    , m_sourceValue(0)
+    , m_itemPool(itemPool)
+    , m_logger(logger)
+    , m_searchPaths(searchPaths)
 {
 }
 
@@ -77,7 +79,7 @@ bool ItemReaderASTVisitor::visit(AST::UiProgram *ast)
 {
     Q_UNUSED(ast);
     m_sourceValue.clear();
-    m_file->m_searchPaths = m_reader->searchPaths();
+    m_file->m_searchPaths = m_searchPaths;
 
     if (Q_UNLIKELY(!ast->members->member))
         throw ErrorInfo(Tr::tr("No root item found in %1.").arg(m_file->filePath()));
@@ -108,7 +110,7 @@ bool ItemReaderASTVisitor::addPrototype(const QString &fileName, const QString &
 void ItemReaderASTVisitor::collectPrototypes(const QString &path, const QString &as)
 {
     QStringList fileNames; // Yes, file *names*.
-    if (m_reader->findDirectoryEntries(path, &fileNames)) {
+    if (m_visitorState.findDirectoryEntries(path, &fileNames)) {
         foreach (const QString &fileName, fileNames)
             addPrototype(fileName, path + QLatin1Char('/') + fileName, as, false);
         return;
@@ -121,12 +123,12 @@ void ItemReaderASTVisitor::collectPrototypes(const QString &path, const QString
         if (addPrototype(fileName, filePath, as, true))
             fileNames << fileName;
     }
-    m_reader->cacheDirectoryEntries(path, fileNames);
+    m_visitorState.cacheDirectoryEntries(path, fileNames);
 }
 
 bool ItemReaderASTVisitor::visit(AST::UiImportList *uiImportList)
 {
-    foreach (const QString &searchPath, m_reader->searchPaths())
+    foreach (const QString &searchPath, m_searchPaths)
         collectPrototypes(searchPath + QLatin1String("/imports"), QString());
 
     const QString path = FileInfo::path(m_file->filePath());
@@ -150,8 +152,8 @@ bool ItemReaderASTVisitor::visit(AST::UiImportList *uiImportList)
             if (isBase)
                 checkImportVersion(import->versionToken);
             else if (import->versionToken.length)
-                m_reader->logger().printWarning(ErrorInfo(Tr::tr("Superfluous version specification."),
-                                                    toCodeLocation(import->versionToken)));
+                m_logger.printWarning(ErrorInfo(Tr::tr("Superfluous version specification."),
+                                                toCodeLocation(import->versionToken)));
         }
 
         QString as;
@@ -169,8 +171,8 @@ bool ItemReaderASTVisitor::visit(AST::UiImportList *uiImportList)
                                                "must not have 'as' specifier.").arg(extensionName));
                     }
                     if (Q_UNLIKELY(m_file->m_jsExtensions.contains(extensionName))) {
-                        m_reader->logger().printWarning(Tr::tr("Built-in extension '%1' already "
-                                                               "imported.").arg(extensionName));
+                        m_logger.printWarning(Tr::tr("Built-in extension '%1' already "
+                                                     "imported.").arg(extensionName));
                     } else {
                         m_file->m_jsExtensions << extensionName;
                     }
@@ -233,7 +235,7 @@ bool ItemReaderASTVisitor::visit(AST::UiImportList *uiImportList)
                     ? QLatin1String("qbs/base") : importUri.join(QDir::separator());
             bool found = m_typeNameToFile.contains(importUri);
             if (!found) {
-                foreach (const QString &searchPath, m_reader->searchPaths()) {
+                foreach (const QString &searchPath, m_searchPaths) {
                     const QFileInfo fi(FileInfo::resolvePath(
                                            FileInfo::resolvePath(searchPath,
                                                                  QLatin1String("imports")),
@@ -279,7 +281,7 @@ bool ItemReaderASTVisitor::visit(AST::UiObjectDefinition *ast)
 {
     const QString typeName = ast->qualifiedTypeNameId->name.toString();
 
-    Item *item = Item::create(m_reader->m_pool);
+    Item *item = Item::create(m_itemPool);
     item->m_file = m_file;
     item->m_parent = m_item;
     item->m_typeName = typeName;
@@ -292,7 +294,7 @@ bool ItemReaderASTVisitor::visit(AST::UiObjectDefinition *ast)
     } else {
         // This is the root item.
         m_item = item;
-        m_readerResult->rootItem = item;
+        m_rootItem = item;
     }
 
     if (ast->initializer) {
@@ -301,7 +303,7 @@ bool ItemReaderASTVisitor::visit(AST::UiObjectDefinition *ast)
         qSwap(m_item, item);
     }
 
-    BuiltinDeclarations::instance().setupItemForBuiltinType(item, m_reader->logger());
+    BuiltinDeclarations::instance().setupItemForBuiltinType(item, m_logger);
 
     if (item->typeName() != QLatin1String("Properties")
             && item->typeName() != QLatin1String("SubProject")) {
@@ -312,14 +314,15 @@ bool ItemReaderASTVisitor::visit(AST::UiObjectDefinition *ast)
     const QStringList fullTypeName = toStringList(ast->qualifiedTypeNameId);
     const QString baseTypeFileName = m_typeNameToFile.value(fullTypeName);
     if (!baseTypeFileName.isEmpty()) {
-        const ItemReaderResult baseFile = m_reader->internalReadFile(baseTypeFileName);
+        const Item * const rootItem
+                = m_visitorState.readFile(baseTypeFileName, m_searchPaths, m_itemPool);
 
-        inheritItem(item, baseFile.rootItem);
-        if (baseFile.rootItem->m_file->m_idScope) {
+        inheritItem(item, rootItem);
+        if (rootItem->m_file->m_idScope) {
             // Make ids from the derived file visible in the base file.
             // ### Do we want to turn off this feature? It's QMLish but kind of strange.
             ensureIdScope(item->m_file);
-            baseFile.rootItem->m_file->m_idScope->setPrototype(item->m_file->m_idScope);
+            rootItem->m_file->m_idScope->setPrototype(item->m_file->m_idScope);
         }
     }
 
@@ -475,7 +478,7 @@ Item *ItemReaderASTVisitor::targetItemForBinding(Item *item,
     for (int i = 0; i < c; ++i) {
         ValuePtr v = targetItem->m_properties.value(bindingName.at(i));
         if (!v) {
-            Item *newItem = Item::create(m_reader->m_pool);
+            Item *newItem = Item::create(m_itemPool);
             v = ItemValue::create(newItem);
             targetItem->m_properties.insert(bindingName.at(i), v);
         }
@@ -556,7 +559,7 @@ void ItemReaderASTVisitor::inheritItem(Item *dst, const Item *src)
 void ItemReaderASTVisitor::ensureIdScope(const FileContextPtr &file)
 {
     if (!file->m_idScope) {
-        file->m_idScope = Item::create(m_reader->m_pool);
+        file->m_idScope = Item::create(m_itemPool);
         file->m_idScope->m_typeName = QLatin1String("IdScope");
     }
 }
diff --git a/src/lib/corelib/language/itemreaderastvisitor.h b/src/lib/corelib/language/itemreaderastvisitor.h
index 60b1fdd94..643c9a1e1 100644
--- a/src/lib/corelib/language/itemreaderastvisitor.h
+++ b/src/lib/corelib/language/itemreaderastvisitor.h
@@ -34,21 +34,23 @@
 #include "item.h"
 #include "filecontext.h"
 
+#include <logging/logger.h>
 #include <parser/qmljsastvisitor_p.h>
 
 #include <QHash>
+#include <QStringList>
 
 namespace qbs {
 namespace Internal {
 
-class ItemReader;
-struct ItemReaderResult;
+class ItemReaderVisitorState;
 class Version;
 
 class ItemReaderASTVisitor : public QbsQmlJS::AST::Visitor
 {
 public:
-    ItemReaderASTVisitor(ItemReader *reader, ItemReaderResult *result);
+    ItemReaderASTVisitor(ItemReaderVisitorState &visitorState,
+                         ItemPool *itemPool, Logger logger, const QStringList &searchPaths);
     ~ItemReaderASTVisitor();
 
     void setFilePath(const QString &filePath);
@@ -61,6 +63,8 @@ public:
     bool visit(QbsQmlJS::AST::UiScriptBinding *ast);
     bool visit(QbsQmlJS::AST::FunctionDeclaration *ast);
 
+    Item *rootItem() const { return m_rootItem; }
+
 private:
     static Version readImportVersion(const QString &str,
             const CodeLocation &location = CodeLocation());
@@ -80,11 +84,14 @@ private:
     bool addPrototype(const QString &fileName, const QString &filePath, const QString &as,
                       bool needsCheck);
 
-    ItemReader *m_reader;
-    ItemReaderResult *m_readerResult;
-    FileContextPtr m_file;
+    ItemReaderVisitorState &m_visitorState;
+    const FileContextPtr m_file;
+    ItemPool * const m_itemPool;
+    Logger m_logger;
+    const QStringList m_searchPaths;
     QHash<QStringList, QString> m_typeNameToFile;
-    Item *m_item;
+    Item *m_item = nullptr;
+    Item *m_rootItem = nullptr;
     JSSourceValuePtr m_sourceValue;
 };
 
diff --git a/src/lib/corelib/language/itemreadervisitorstate.cpp b/src/lib/corelib/language/itemreadervisitorstate.cpp
new file mode 100644
index 000000000..4eeb7df38
--- /dev/null
+++ b/src/lib/corelib/language/itemreadervisitorstate.cpp
@@ -0,0 +1,168 @@
+/****************************************************************************
+**
+** Copyright (C) 2015 The Qt Company Ltd.
+** Contact: http://www.qt.io/licensing
+**
+** This file is part of the Qt Build Suite.
+**
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms and
+** conditions see http://www.qt.io/terms-conditions. For further information
+** use the contact form at http://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 or version 3 as published by the Free
+** Software Foundation and appearing in the file LICENSE.LGPLv21 and
+** LICENSE.LGPLv3 included in the packaging of this file.  Please review the
+** following information to ensure the GNU Lesser General Public License
+** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
+** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, The Qt Company gives you certain additional
+** rights.  These rights are described in The Qt Company LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+****************************************************************************/
+#include "itemreadervisitorstate.h"
+
+#include "asttools.h"
+#include "itemreaderastvisitor.h"
+
+#include <logging/translator.h>
+#include <parser/qmljsengine_p.h>
+#include <parser/qmljslexer_p.h>
+#include <parser/qmljsparser_p.h>
+#include <tools/error.h>
+
+#include <QExplicitlySharedDataPointer>
+#include <QFile>
+#include <QFileInfo>
+#include <QSharedData>
+#include <QTextStream>
+
+namespace qbs {
+namespace Internal {
+
+class ASTCacheValueData : public QSharedData
+{
+    Q_DISABLE_COPY(ASTCacheValueData)
+public:
+    ASTCacheValueData()
+        : ast(0)
+        , processing(false)
+    {
+    }
+
+    QString code;
+    QbsQmlJS::Engine engine;
+    QbsQmlJS::AST::UiProgram *ast;
+    bool processing;
+};
+
+class ASTCacheValue
+{
+public:
+    ASTCacheValue()
+        : d(new ASTCacheValueData)
+    {
+    }
+
+    ASTCacheValue(const ASTCacheValue &other)
+        : d(other.d)
+    {
+    }
+
+    void setProcessingFlag(bool b) { d->processing = b; }
+    bool isProcessing() const { return d->processing; }
+
+    void setCode(const QString &code) { d->code = code; }
+    QString code() const { return d->code; }
+
+    QbsQmlJS::Engine *engine() const { return &d->engine; }
+
+    void setAst(QbsQmlJS::AST::UiProgram *ast) { d->ast = ast; }
+    QbsQmlJS::AST::UiProgram *ast() const { return d->ast; }
+    bool isValid() const { return d->ast; }
+
+private:
+    QExplicitlySharedDataPointer<ASTCacheValueData> d;
+};
+
+class ItemReaderVisitorState::ASTCache : public QHash<QString, ASTCacheValue> {};
+
+
+ItemReaderVisitorState::ItemReaderVisitorState(Logger logger)
+    : m_logger(logger)
+    , m_astCache(new ASTCache)
+{
+
+}
+
+ItemReaderVisitorState::~ItemReaderVisitorState()
+{
+    delete m_astCache;
+}
+
+Item *ItemReaderVisitorState::readFile(const QString &filePath, const QStringList &searchPaths,
+                                  ItemPool *itemPool)
+{
+    ASTCacheValue &cacheValue = (*m_astCache)[filePath];
+    if (cacheValue.isValid()) {
+        if (Q_UNLIKELY(cacheValue.isProcessing()))
+            throw ErrorInfo(Tr::tr("Loop detected when importing '%1'.").arg(filePath));
+    } else {
+        QFile file(filePath);
+        if (Q_UNLIKELY(!file.open(QFile::ReadOnly)))
+            throw ErrorInfo(Tr::tr("Cannot open '%1'.").arg(filePath));
+
+        m_filesRead.insert(filePath);
+        const QString code = QTextStream(&file).readAll();
+        QbsQmlJS::Lexer lexer(cacheValue.engine());
+        lexer.setCode(code, 1);
+        QbsQmlJS::Parser parser(cacheValue.engine());
+
+        file.close();
+        if (!parser.parse()) {
+            QList<QbsQmlJS::DiagnosticMessage> parserMessages = parser.diagnosticMessages();
+            if (Q_UNLIKELY(!parserMessages.isEmpty())) {
+                ErrorInfo err;
+                foreach (const QbsQmlJS::DiagnosticMessage &msg, parserMessages)
+                    err.append(msg.message, toCodeLocation(filePath, msg.loc));
+                throw err;
+            }
+        }
+
+        cacheValue.setCode(code);
+        cacheValue.setAst(parser.ast());
+    }
+
+    ItemReaderASTVisitor astVisitor(*this, itemPool, m_logger, searchPaths);
+    astVisitor.setFilePath(QFileInfo(filePath).absoluteFilePath());
+    astVisitor.setSourceCode(cacheValue.code());
+    cacheValue.setProcessingFlag(true);
+    cacheValue.ast()->accept(&astVisitor);
+    cacheValue.setProcessingFlag(false);
+    return astVisitor.rootItem();
+}
+
+void ItemReaderVisitorState::cacheDirectoryEntries(const QString &dirPath, const QStringList &entries)
+{
+    m_directoryEntries.insert(dirPath, entries);
+}
+
+bool ItemReaderVisitorState::findDirectoryEntries(const QString &dirPath, QStringList *entries) const
+{
+    const auto it = m_directoryEntries.constFind(dirPath);
+    if (it == m_directoryEntries.constEnd())
+        return false;
+    *entries = it.value();
+    return true;
+}
+
+
+} // namespace Internal
+} // namespace qbs
diff --git a/src/lib/corelib/language/itemreadervisitorstate.h b/src/lib/corelib/language/itemreadervisitorstate.h
new file mode 100644
index 000000000..40c13c835
--- /dev/null
+++ b/src/lib/corelib/language/itemreadervisitorstate.h
@@ -0,0 +1,70 @@
+/****************************************************************************
+**
+** Copyright (C) 2015 The Qt Company Ltd.
+** Contact: http://www.qt.io/licensing
+**
+** This file is part of the Qt Build Suite.
+**
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms and
+** conditions see http://www.qt.io/terms-conditions. For further information
+** use the contact form at http://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 or version 3 as published by the Free
+** Software Foundation and appearing in the file LICENSE.LGPLv21 and
+** LICENSE.LGPLv3 included in the packaging of this file.  Please review the
+** following information to ensure the GNU Lesser General Public License
+** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
+** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, The Qt Company gives you certain additional
+** rights.  These rights are described in The Qt Company LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+****************************************************************************/
+#ifndef QBS_ITEMREADERVISITORSTATE_H
+#define QBS_ITEMREADERVISITORSTATE_H
+
+#include <logging/logger.h>
+
+#include <QSet>
+#include <QStack>
+#include <QStringList>
+
+namespace qbs {
+namespace Internal {
+class BuiltinDeclarations;
+class Item;
+class ItemPool;
+
+class ItemReaderVisitorState
+{
+public:
+    ItemReaderVisitorState(Logger logger);
+    ~ItemReaderVisitorState();
+
+    QSet<QString> filesRead() const { return m_filesRead; }
+
+    Item *readFile(const QString &filePath, const QStringList &searchPaths, ItemPool *itemPool);
+
+    void cacheDirectoryEntries(const QString &dirPath, const QStringList &entries);
+    bool findDirectoryEntries(const QString &dirPath, QStringList *entries) const;
+
+private:
+    Logger m_logger;
+    QSet<QString> m_filesRead;
+    QHash<QString, QStringList> m_directoryEntries;
+
+    class ASTCache;
+    ASTCache * const m_astCache;
+};
+
+} // namespace Internal
+} // namespace qbs
+
+#endif // Include guard.
diff --git a/src/lib/corelib/language/language.pri b/src/lib/corelib/language/language.pri
index 7c984176f..68c8139d7 100644
--- a/src/lib/corelib/language/language.pri
+++ b/src/lib/corelib/language/language.pri
@@ -21,6 +21,7 @@ HEADERS += \
     $$PWD/itempool.h \
     $$PWD/itemreader.h \
     $$PWD/itemreaderastvisitor.h \
+    $$PWD/itemreadervisitorstate.h \
     $$PWD/jsimports.h \
     $$PWD/language.h \
     $$PWD/loader.h \
@@ -53,6 +54,7 @@ SOURCES += \
     $$PWD/itempool.cpp \
     $$PWD/itemreader.cpp \
     $$PWD/itemreaderastvisitor.cpp \
+    $$PWD/itemreadervisitorstate.cpp \
     $$PWD/language.cpp \
     $$PWD/loader.cpp \
     $$PWD/moduleloader.cpp \