FIX #15144 add tooltip on fields in identify window / attribute window / feature form

- added new `QString QgsField::displayType( const bool showConstraints = false )` to unify the display of field types whenever length or precision are present
- added new argument `expression` to `QgsFieldModel::fieldToolTip( const QgsField &field, const QString &expression = QStringLiteral() )`. Now the tooltip shows "<alias> (<field>)\n<type>\n<comment>\n<expression>" with appropriate formatting
- added meaningful field tooltips in the "Identify Results" dialog
- field tooltips show the same content in "Feature Attributes" form, "Attribute Table" and "Identify Tool"

Fixes #15144

python/core/auto_generated/qgsfield.sip.in

@@ -104,6 +104,18 @@ represents.
 .. versionadded:: 3.12
 %End
 
+
+    QString displayType( bool showConstraints = false ) const;
+%Docstring
+Returns the type to use when displaying this field, including the length and precision of the datatype if applicable.
+
+This will be used when the full datatype with details has to displayed to the user.
+
+.. seealso:: :py:func:`type`
+
+.. versionadded:: 3.14
+%End
+
     QVariant::Type type() const;
 %Docstring
 Gets variant type of the field as it will be retrieved from data source

python/core/auto_generated/qgsfieldmodel.sip.in

@@ -128,7 +128,7 @@ Returns the layer associated with the model.
     virtual QVariant data( const QModelIndex &index, int role ) const;
 
 
-    static QString fieldToolTip( const QgsField &field );
+    static QString fieldToolTip( const QgsField &field, const QString &expression = QString() );
 %Docstring
 Returns a HTML formatted tooltip string for a ``field``, containing details
 like the field name, alias and type.

src/app/qgsidentifyresultsdialog.cpp

@@ -78,6 +78,7 @@
 #include "qgsfiledownloaderdialog.h"
 #include "qgsfieldformatterregistry.h"
 #include "qgsfieldformatter.h"
+#include "qgsfieldmodel.h"
 #include "qgssettings.h"
 #include "qgsgui.h"
 #include "qgsexpressioncontextutils.h"
@@ -625,8 +626,11 @@ void QgsIdentifyResultsDialog::addFeature( QgsVectorLayer *vlayer, const QgsFeat
     QgsTreeWidgetItem *attrItem = new QgsTreeWidgetItem( QStringList() << QString::number( i ) << value );
     featItem->addChild( attrItem );
 
+    QString expressionString = fields.fieldOrigin( i ) == QgsFields::OriginExpression
+                               ? vlayer->expressionField( i )
+                               : QStringLiteral();
     attrItem->setData( 0, Qt::DisplayRole, vlayer->attributeDisplayName( i ) );
-    attrItem->setToolTip( 0, vlayer->attributeDisplayName( i ) );
+    attrItem->setToolTip( 0, QgsFieldModel::fieldToolTip( fields.at( i ), expressionString ) );
     attrItem->setData( 0, Qt::UserRole, fields.at( i ).name() );
     attrItem->setData( 0, Qt::UserRole + 1, i );
 

src/core/qgsfield.cpp

@@ -103,6 +103,29 @@ QString QgsField::displayNameWithAlias() const
   return QStringLiteral( "%1 (%2)" ).arg( name() ).arg( alias() );
 }
 
+QString QgsField::displayType( const bool showConstraints ) const
+{
+  QString typeStr = typeName();
+
+  if ( length() > 0 && precision() > 0 )
+    typeStr += QStringLiteral( "(%1, %2)" ).arg( length() ).arg( precision() );
+  else if ( length() > 0 )
+    typeStr += QStringLiteral( "(%1)" ).arg( length() );
+
+  if ( showConstraints )
+  {
+    typeStr += constraints().constraints() & QgsFieldConstraints::ConstraintNotNull
+               ? QStringLiteral( " NOT NULL" )
+               : QStringLiteral( " NULL" );
+
+    typeStr += constraints().constraints() & QgsFieldConstraints::ConstraintUnique
+               ? QStringLiteral( " UNIQUE" )
+               : QStringLiteral( "" );
+  }
+
+  return typeStr;
+}
+
 QVariant::Type QgsField::type() const
 {
   return d->type;

src/core/qgsfield.h

@@ -130,6 +130,17 @@ class CORE_EXPORT QgsField
      */
     QString displayNameWithAlias() const;
 
+
+    /**
+     * Returns the type to use when displaying this field, including the length and precision of the datatype if applicable.
+     *
+     * This will be used when the full datatype with details has to displayed to the user.
+     *
+     * \see type()
+     * \since QGIS 3.14
+     */
+    QString displayType( bool showConstraints = false ) const;
+
     //! Gets variant type of the field as it will be retrieved from data source
     QVariant::Type type() const;
 

src/core/qgsfieldmodel.cpp

@@ -464,7 +464,7 @@ QVariant QgsFieldModel::data( const QModelIndex &index, int role ) const
   }
 }
 
-QString QgsFieldModel::fieldToolTip( const QgsField &field )
+QString QgsFieldModel::fieldToolTip( const QgsField &field, const QString &expression )
 {
   QString toolTip;
   if ( !field.alias().isEmpty() )
@@ -475,23 +475,21 @@ QString QgsFieldModel::fieldToolTip( const QgsField &field )
   {
     toolTip = QStringLiteral( "<b>%1</b>" ).arg( field.name() );
   }
-  QString typeString;
-  if ( field.length() > 0 )
+
+  toolTip += QStringLiteral( "<br><font style='font-family:monospace; white-space: nowrap;'>%3</font>" ).arg( field.displayType( true ) );
+
+  QString comment = field.comment();
+
+  if ( ! comment.isEmpty() )
   {
-    if ( field.precision() > 0 )
-    {
-      typeString = QStringLiteral( "%1 (%2, %3)" ).arg( field.typeName() ).arg( field.length() ).arg( field.precision() );
-    }
-    else
-    {
-      typeString = QStringLiteral( "%1 (%2)" ).arg( field.typeName() ).arg( field.length() );
-    }
+    toolTip += QStringLiteral( "<br><em>%1</em>" ).arg( comment );
   }
-  else
+
+  if ( ! expression.isEmpty() )
   {
-    typeString = field.typeName();
+    toolTip += QStringLiteral( "<br><font style='font-family:monospace;'>%3</font>" ).arg( expression );
   }
-  toolTip += QStringLiteral( "<p>%1</p>" ).arg( typeString );
+
   return toolTip;
 }
 

src/core/qgsfieldmodel.h

@@ -135,7 +135,7 @@ class CORE_EXPORT QgsFieldModel : public QAbstractItemModel
      * like the field name, alias and type.
      * \since QGIS 3.0
      */
-    static QString fieldToolTip( const QgsField &field );
+    static QString fieldToolTip( const QgsField &field, const QString &expression = QString() );
 
     /**
      * Manually sets the \a fields to use for the model.

src/gui/attributetable/qgsattributetablemodel.cpp

@@ -624,7 +624,10 @@ QVariant QgsAttributeTableModel::headerData( int section, Qt::Orientation orient
     else
     {
       const QgsField field = layer()->fields().at( mAttributes.at( section ) );
-      return QgsFieldModel::fieldToolTip( field );
+      QString expressionString = layer()->fields().fieldOrigin( mAttributes.at( section ) ) == QgsFields::OriginExpression
+                                 ? layer()->expressionField( mAttributes.at( section ) )
+                                 : QStringLiteral();
+      return QgsFieldModel::fieldToolTip( field, expressionString );
     }
   }
   else

src/gui/qgsattributeform.cpp

@@ -43,6 +43,7 @@
 #include "qgsexpressioncontextutils.h"
 #include "qgsfeaturerequest.h"
 #include "qgstexteditwrapper.h"
+#include "qgsfieldmodel.h"
 
 #include <QDir>
 #include <QTextStream>
@@ -1505,8 +1506,11 @@ void QgsAttributeForm::init()
       bool labelOnTop = mLayer->editFormConfig().labelOnTop( idx );
 
       // This will also create the widget
+      QString expressionString = fields.fieldOrigin( idx ) == QgsFields::OriginExpression
+                                 ? mLayer->expressionField( idx )
+                                 : QStringLiteral();
       QLabel *l = new QLabel( labelText );
-      l->setToolTip( QStringLiteral( "<b>%1</b><p>%2</p>" ).arg( fieldName, field.comment() ) );
+      l->setToolTip( QgsFieldModel::fieldToolTip( field, expressionString ) );
       QSvgWidget *i = new QSvgWidget();
       i->setFixedSize( 18, 18 );
 

tests/src/core/testqgsfield.cpp

@@ -48,6 +48,7 @@ class TestQgsField: public QObject
     void dataStream();
     void displayName();
     void displayNameWithAlias();
+    void displayType();
     void editorWidgetSetup();
     void collection();
 
@@ -752,6 +753,24 @@ void TestQgsField::displayNameWithAlias()
 }
 
 
+void TestQgsField::displayType()
+{
+  QgsField field;
+  field.setTypeName( QStringLiteral( "numeric" ) );
+  QCOMPARE( field.displayType(), QString( "numeric" ) );
+  field.setLength( 20 );
+  QCOMPARE( field.displayType(), QString( "numeric(20)" ) );
+  field.setPrecision( 10 );
+  field.setPrecision( 10 );
+  QCOMPARE( field.displayType(), QString( "numeric(20, 10)" ) );
+  QCOMPARE( field.displayType( true ), QString( "numeric(20, 10) NULL" ) );
+  QgsFieldConstraints constraints;
+  constraints.setConstraint( QgsFieldConstraints::ConstraintUnique );
+  field.setConstraints( constraints );
+  QCOMPARE( field.displayType( true ), QString( "numeric(20, 10) NULL UNIQUE" ) );
+}
+
+
 void TestQgsField::editorWidgetSetup()
 {
   QgsField field;

tests/src/python/test_qgsfieldmodel.py

@@ -19,7 +19,8 @@ from qgis.core import (QgsField,
                        QgsFieldProxyModel,
                        QgsEditorWidgetSetup,
                        QgsProject,
-                       QgsVectorLayerJoinInfo)
+                       QgsVectorLayerJoinInfo,
+                       QgsFieldConstraints)
 from qgis.PyQt.QtCore import QVariant, Qt, QModelIndex
 
 from qgis.testing import start_app, unittest
@@ -350,13 +351,21 @@ class TestQgsFieldModel(unittest.TestCase):
 
     def testFieldTooltip(self):
         f = QgsField('my_string', QVariant.String, 'string')
-        self.assertEqual(QgsFieldModel.fieldToolTip(f), '<b>my_string</b><p>string</p>')
+        self.assertEqual(QgsFieldModel.fieldToolTip(f), "<b>my_string</b><br><font style='font-family:monospace; white-space: nowrap;'>string NULL</font>")
         f.setAlias('my alias')
-        self.assertEqual(QgsFieldModel.fieldToolTip(f), '<b>my alias</b> (my_string)<p>string</p>')
+        self.assertEqual(QgsFieldModel.fieldToolTip(f), "<b>my alias</b> (my_string)<br><font style='font-family:monospace; white-space: nowrap;'>string NULL</font>")
         f.setLength(20)
-        self.assertEqual(QgsFieldModel.fieldToolTip(f), '<b>my alias</b> (my_string)<p>string (20)</p>')
+        self.assertEqual(QgsFieldModel.fieldToolTip(f), "<b>my alias</b> (my_string)<br><font style='font-family:monospace; white-space: nowrap;'>string(20) NULL</font>")
         f = QgsField('my_real', QVariant.Double, 'real', 8, 3)
-        self.assertEqual(QgsFieldModel.fieldToolTip(f), '<b>my_real</b><p>real (8, 3)</p>')
+        self.assertEqual(QgsFieldModel.fieldToolTip(f), "<b>my_real</b><br><font style='font-family:monospace; white-space: nowrap;'>real(8, 3) NULL</font>")
+        f.setComment('Comment text')
+        self.assertEqual(QgsFieldModel.fieldToolTip(f), "<b>my_real</b><br><font style='font-family:monospace; white-space: nowrap;'>real(8, 3) NULL</font><br><em>Comment text</em>")
+        self.assertEqual(QgsFieldModel.fieldToolTip(f, '1+1'), "<b>my_real</b><br><font style='font-family:monospace; white-space: nowrap;'>real(8, 3) NULL</font><br><em>Comment text</em><br><font style='font-family:monospace;'>1+1</font>")
+        f.setAlias('my alias')
+        constraints = f.constraints()
+        constraints.setConstraint(QgsFieldConstraints.ConstraintUnique)
+        f.setConstraints(constraints)
+        self.assertEqual(QgsFieldModel.fieldToolTip(f, '1+1'), "<b>my alias</b> (my_real)<br><font style='font-family:monospace; white-space: nowrap;'>real(8, 3) NULL UNIQUE</font><br><em>Comment text</em><br><font style='font-family:monospace;'>1+1</font>")
 
 
 if __name__ == '__main__':