[libcalamares] Add nested (dotted) key lookup for GS

src/libcalamares/GlobalStorage.cpp

@@ -190,4 +190,55 @@ GlobalStorage::loadYaml( const QString& filename )
     return false;
 }
 
+///@brief Implementation for recursively looking up dotted selector parts.
+static QVariant
+lookup( const QStringList& nestedKey, int index, const QVariant& v, bool& ok )
+{
+    if ( !v.canConvert< QVariantMap >() )
+    {
+        // Mismatch: we're still looking for keys, but v is not a submap
+        ok = false;
+        return {};
+    }
+    if ( index >= nestedKey.length() )
+    {
+        cError() << "Recursion error looking at index" << index << "of" << nestedKey;
+        ok = false;
+        return {};
+    }
+
+    const QVariantMap map = v.toMap();
+    const QString& key = nestedKey.at( index );
+    if ( index == nestedKey.length() - 1 )
+    {
+        ok = map.contains( key );
+        return ok ? map.value( key ) : QVariant();
+    }
+    else
+    {
+        return lookup( nestedKey, index + 1, map.value( key ), ok );
+    }
+}
+
+QVariant
+lookup( const GlobalStorage* storage, const QString& nestedKey, bool& ok )
+{
+    ok = false;
+    if ( !storage )
+    {
+        return {};
+    }
+
+    if ( nestedKey.contains( '.' ) )
+    {
+        QStringList steps = nestedKey.split( '.' );
+        return lookup( steps, 1, storage->value( steps.first() ), ok );
+    }
+    else
+    {
+        ok = storage->contains( nestedKey );
+        return ok ? storage->value( nestedKey ) : QVariant();
+    }
+}
+
 }  // namespace Calamares

src/libcalamares/GlobalStorage.h

@@ -167,6 +167,26 @@ private:
     mutable QMutex m_mutex;
 };
 
+
+/** @brief Gets a value from the store
+ *
+ * When @p nestedKey contains no '.' characters, equivalent
+ * to `gs->value(nestedKey)`. Otherwise recursively looks up
+ * the '.'-separated parts of @p nestedKey in successive sub-maps
+ * of the store, returning the value in the innermost one.
+ *
+ * Example: `lookup(gs, "branding.name")` finds the value of the
+ * 'name' key in the 'branding' submap of the store.
+ *
+ * Sets @p ok to @c true if a value was found. Returns the value
+ * as a variant. If no value is found (e.g. the key is missing
+ * or some prefix submap is missing) sets @p ok to @c false
+ * and returns an invalid QVariant.
+ *
+ * @see GlobalStorage::value
+ */
+DLLEXPORT QVariant lookup( const GlobalStorage* gs, const QString& nestedKey, bool& ok );
+
 }  // namespace Calamares
 
 #endif  // CALAMARES_GLOBALSTORAGE_H

src/libcalamares/Tests.cpp

@@ -32,6 +32,7 @@ private Q_SLOTS:
     void testGSLoadSave();
     void testGSLoadSave2();
     void testGSLoadSaveYAMLStringList();
+    void testGSNestedLookup();
 
     void testInstanceKey();
     void testInstanceDescription();
@@ -177,6 +178,38 @@ TestLibCalamares::testGSLoadSaveYAMLStringList()
     QCOMPARE( gs2.value( "dwarfs" ).toString(), QStringLiteral( "<QStringList>" ) );  // .. they're gone
 }
 
+void
+TestLibCalamares::testGSNestedLookup()
+{
+    Logger::setupLogLevel( Logger::LOGDEBUG );
+
+    const QString filename( BUILD_AS_TEST "/testdata/yaml-list.conf" );
+    QVERIFY2( QFile::exists( filename ), qPrintable( filename ) );
+
+    Calamares::GlobalStorage gs2;
+    QVERIFY( gs2.loadYaml( filename ) );
+
+    bool ok = false;
+    const auto v0 = Calamares::lookup( &gs2, "horse.colors.neck", ok );
+    QVERIFY( ok );
+    QVERIFY( v0.canConvert< QString >() );
+    QCOMPARE( v0.toString(), QStringLiteral( "roan" ) );
+    const auto v1 = Calamares::lookup( &gs2, "horse.colors.nose", ok );
+    QVERIFY( !ok );
+    QVERIFY( !v1.isValid() );
+    const auto v2 = Calamares::lookup( &gs2, "cow.colors.nose", ok );
+    QVERIFY( !ok );
+    QVERIFY( !v2.isValid() );
+    const auto v3 = Calamares::lookup( &gs2, "dwarfs", ok );
+    QVERIFY( ok );
+    QVERIFY( v3.canConvert< QVariantList >() );  // because it's a list-valued thing
+    const auto v4 = Calamares::lookup( &gs2, "dwarfs.sleepy", ok );
+    QVERIFY( !ok );  // Sleepy is a value in the list of dwarfs, not a key
+    const auto v5 = Calamares::lookup( &gs2, "derp", ok );
+    QVERIFY( ok );
+    QCOMPARE( v5.toInt(), 17 );
+}
+
 void
 TestLibCalamares::testInstanceKey()
 {

src/libcalamares/testdata/yaml-list.conf

@@ -9,3 +9,9 @@
     - "sleepy"
     - "sneezy"
     - "doc"
+horse:
+    hoofs: 4
+    colors:
+        mane: black
+        neck: roan
+        tail: white