Expose DB fields to the browser

python/core/auto_generated/qgsdataitem.sip.in

@@ -49,6 +49,8 @@ Parent/children hierarchy is not based on QObject.
       Favorites,
       Project,
       Custom,
+      Fields,
+      Field,
     };
 
 
@@ -900,6 +902,89 @@ Creates a new data item from the specified path.
 };
 
 
+class QgsFieldsItem : QgsDataItem
+{
+%Docstring
+A collection of fields item
+
+.. versionadded:: 3.16
+%End
+
+%TypeHeaderCode
+#include "qgsdataitem.h"
+%End
+  public:
+
+    QgsFieldsItem( QgsDataItem *parent /TransferThis/,
+                   const QString &name,
+                   const QString &path,
+                   const QString &providerKey,
+                   const QString schema,
+                   const QString tableName );
+%Docstring
+Constructor for QgsFieldsItem, with the specified ``parent`` item.
+
+The ``path`` argument gives the item path in the browser tree. The ``path`` string can take any form,
+but QgsDataItem items pointing to different logical locations should always use a different item ``path``.
+
+The ``providerKey`` string (added in QGIS 3.12) can be used to specify the key for the QgsDataItemProvider that created this item.
+The ``name`` argument specifies the text to show in the model for the item. A translated string should
+be used wherever appropriate.
+%End
+
+    ~QgsFieldsItem();
+
+    virtual QVector<QgsDataItem *> createChildren();
+
+
+    virtual QIcon icon();
+
+
+  protected:
+
+    static QIcon openFieldsIcon();
+%Docstring
+Shared open fields icon.
+%End
+
+    static QIcon fieldsIcon();
+%Docstring
+Shared closed fields icon.
+%End
+
+};
+
+
+class QgsFieldItem : QgsDataItem
+{
+%Docstring
+A layer field item
+
+.. versionadded:: 3.16
+%End
+
+%TypeHeaderCode
+#include "qgsdataitem.h"
+%End
+  public:
+
+    QgsFieldItem( QgsDataItem *parent /TransferThis/,
+                  const QgsField &field );
+%Docstring
+Constructor for QgsFieldItem, with the specified ``parent`` item and /a field.
+The ``name`` argument specifies the text to show in the model for the item. A translated string should
+be used wherever appropriate.
+%End
+
+    ~QgsFieldItem();
+
+    virtual QIcon icon();
+
+
+};
+
+
+
 
 
 

src/core/providers/ogr/qgsgeopackagedataitems.cpp

@@ -315,7 +315,16 @@ QgsGeoPackageCollectionItem *QgsGeoPackageAbstractLayerItem::collection() const
 QgsGeoPackageVectorLayerItem::QgsGeoPackageVectorLayerItem( QgsDataItem *parent, const QString &name, const QString &path, const QString &uri, LayerType layerType )
   : QgsGeoPackageAbstractLayerItem( parent, name, path, uri, layerType, QStringLiteral( "ogr" ) )
 {
-  mCapabilities |= Rename;
+  mCapabilities |= ( Rename | Fertile );
+  setState( QgsDataItem::State::NotPopulated );
+}
+
+
+QVector<QgsDataItem *> QgsGeoPackageVectorLayerItem::createChildren()
+{
+  QVector<QgsDataItem *> children;
+  children.push_back( new QgsFieldsItem( this, tr( "Columns" ), uri() + QStringLiteral( "/columns/ " ), providerKey(), QString(), name() ) );
+  return children;
 }
 
 

src/core/providers/ogr/qgsgeopackagedataitems.h

@@ -126,6 +126,8 @@ class CORE_EXPORT QgsGeoPackageVectorLayerItem final: public QgsGeoPackageAbstra
     QgsGeoPackageVectorLayerItem( QgsDataItem *parent, const QString &name, const QString &path, const QString &uri, LayerType layerType );
     bool executeDeleteLayer( QString &errCause ) override;
 
+    // QgsDataItem interface
+    QVector<QgsDataItem *> createChildren() override;
 };
 
 /**

src/core/qgsdataitem.cpp

@@ -43,6 +43,7 @@
 #include "qgsanimatedicon.h"
 #include "qgsproject.h"
 #include "qgsvectorlayer.h"
+#include "qgsprovidermetadata.h"
 
 // use GDAL VSI mechanism
 #define CPL_SUPRESS_CPLUSPLUS  //#spellok
@@ -110,6 +111,82 @@ QIcon QgsDataCollectionItem::iconDir()
   return QgsApplication::getThemeIcon( QStringLiteral( "/mIconFolder.svg" ) );
 }
 
+
+QgsFieldsItem::QgsFieldsItem( QgsDataItem *parent,
+                              const QString &name,
+                              const QString &path,
+                              const QString &providerKey,
+                              const QString schema,
+                              const QString tableName )
+  : QgsDataItem( QgsDataItem::Fields, parent, name, path, providerKey )
+  , mSchema( schema )
+  , mTableName( tableName )
+{
+  mCapabilities |= ( Fertile | Collapse );
+}
+
+QgsFieldsItem::~QgsFieldsItem()
+{
+
+}
+
+QVector<QgsDataItem *> QgsFieldsItem::createChildren()
+{
+  QVector<QgsDataItem *> children;
+  try
+  {
+    QgsProviderMetadata *md { QgsProviderRegistry::instance()->providerMetadata( providerKey() ) };
+    if ( md )
+    {
+      QgsAbstractDatabaseProviderConnection *conn { static_cast<QgsAbstractDatabaseProviderConnection *>( md->createConnection( parent()->path( ), {} ) ) };
+      if ( conn )
+      {
+        const QgsFields constFields { conn->fields( mSchema, mTableName ) };
+        for ( const auto &f : constFields )
+        {
+          children.push_back( new QgsFieldItem( this, f ) );
+        }
+      }
+    }
+  }
+  catch ( const QgsProviderConnectionException &ex )
+  {
+    children.push_back( new QgsErrorItem( this, ex.what(), path() + QStringLiteral( "/error" ) ) );
+  }
+  return children;
+}
+
+QIcon QgsFieldsItem::icon()
+{
+  return state() == Populated ? openFieldsIcon() : fieldsIcon();
+}
+
+QIcon QgsFieldsItem::openFieldsIcon()
+{
+  return QgsApplication::getThemeIcon( QStringLiteral( "/mSourceFields.svg" ) );
+}
+
+QIcon QgsFieldsItem::fieldsIcon()
+{
+  return QgsApplication::getThemeIcon( QStringLiteral( "/mSourceFields.svg" ) );
+}
+
+QgsFieldItem::QgsFieldItem( QgsDataItem *parent, const QgsField &field )
+  : QgsDataItem( QgsDataItem::Type::Field, parent, field.name(), parent->path() + '/' + field.name(), parent->providerKey() )
+  , mField( field )
+{
+  setState( QgsDataItem::State::Populated );
+}
+
+QgsFieldItem::~QgsFieldItem()
+{
+}
+
+QIcon QgsFieldItem::icon()
+{
+  return QgsFields::iconForFieldType( mField.type() );
+}
+
 QIcon QgsFavoritesItem::iconFavorites()
 {
   return QgsApplication::getThemeIcon( QStringLiteral( "/mIconFavourites.svg" ) );

src/core/qgsdataitem.h

@@ -82,6 +82,8 @@ class CORE_EXPORT QgsDataItem : public QObject
       Favorites, //!< Represents a favorite item
       Project, //!< Represents a QGIS project
       Custom, //!< Custom item type
+      Fields, //!< Collection of fields
+      Field, //!< Vector layer field
     };
 
     Q_ENUM( Type )
@@ -895,6 +897,89 @@ class CORE_EXPORT QgsZipItem : public QgsDataCollectionItem
 };
 
 
+/**
+ * \ingroup core
+ * A collection of fields item
+ * \since QGIS 3.16
+*/
+class CORE_EXPORT QgsFieldsItem : public QgsDataItem
+{
+    Q_OBJECT
+  public:
+
+    /**
+     * Constructor for QgsFieldsItem, with the specified \a parent item.
+     *
+     * The \a path argument gives the item path in the browser tree. The \a path string can take any form,
+     * but QgsDataItem items pointing to different logical locations should always use a different item \a path.
+     *
+     * The \a providerKey string (added in QGIS 3.12) can be used to specify the key for the QgsDataItemProvider that created this item.
+     * The \a name argument specifies the text to show in the model for the item. A translated string should
+     * be used wherever appropriate.
+     */
+    QgsFieldsItem( QgsDataItem *parent SIP_TRANSFERTHIS,
+                   const QString &name,
+                   const QString &path,
+                   const QString &providerKey,
+                   const QString schema,
+                   const QString tableName );
+
+    ~QgsFieldsItem() override;
+
+    QVector<QgsDataItem *> createChildren() override;
+
+    QIcon icon() override;
+
+  protected:
+
+    /**
+     * Shared open fields icon.
+     */
+    static QIcon openFieldsIcon();
+
+    /**
+     * Shared closed fields icon.
+     */
+    static QIcon fieldsIcon();
+
+  private:
+
+    QString mSchema;
+    QString mTableName;
+};
+
+
+/**
+ * \ingroup core
+ * A layer field item
+ * \since QGIS 3.16
+*/
+class CORE_EXPORT QgsFieldItem : public QgsDataItem
+{
+    Q_OBJECT
+  public:
+
+    /**
+     * Constructor for QgsFieldItem, with the specified \a parent item and /a field.
+     * The \a name argument specifies the text to show in the model for the item. A translated string should
+     * be used wherever appropriate.
+     */
+    QgsFieldItem( QgsDataItem *parent SIP_TRANSFERTHIS,
+                  const QgsField &field );
+
+    ~QgsFieldItem() override;
+
+    // QgsDataItem interface
+    QIcon icon() override;
+
+  private:
+
+    const QgsField mField;
+
+};
+
+
+
 ///@cond PRIVATE
 #ifndef SIP_RUN
 

src/providers/postgres/qgspostgresdataitems.cpp

@@ -314,9 +314,9 @@ QgsPGLayerItem::QgsPGLayerItem( QgsDataItem *parent, const QString &name, const
   : QgsLayerItem( parent, name, path, QString(), layerType, layerProperty.isRaster ? QStringLiteral( "postgresraster" ) : QStringLiteral( "postgres" ) )
   , mLayerProperty( layerProperty )
 {
-  mCapabilities |= Delete;
+  mCapabilities |= Delete | Fertile;
   mUri = createUri();
-  setState( Populated );
+  setState( NotPopulated );
   Q_ASSERT( mLayerProperty.size() == 1 );
 }
 
@@ -576,3 +576,10 @@ bool QgsPGSchemaItem::layerCollection() const
 {
   return true;
 }
+
+QVector<QgsDataItem *> QgsPGLayerItem::createChildren()
+{
+  QVector<QgsDataItem *> children;
+  children.push_back( new QgsFieldsItem( this, tr( "Columns" ), uri() + QStringLiteral( "/columns/ " ), providerKey(), mLayerProperty.schemaName, mLayerProperty.tableName ) );
+  return children;
+}

src/providers/postgres/qgspostgresdataitems.h

@@ -100,10 +100,15 @@ class QgsPGLayerItem : public QgsLayerItem
 
     const QgsPostgresLayerProperty &layerInfo() const { return mLayerProperty; }
 
+    QVector<QgsDataItem *> createChildren() override;
+
   private:
     QgsPostgresLayerProperty mLayerProperty;
+
 };
 
+
+
 //! Provider for Postgres data item
 class QgsPostgresDataItemProvider : public QgsDataItemProvider
 {