Always use string comparison in expressions for string fields

Fixes #13204

Author: nyalldawson

src/core/qgsexpression.cpp

@@ -4161,9 +4161,11 @@ QVariant QgsExpression::NodeBinaryOperator::eval( QgsExpression *parent, const Q
       {
         return TVL_Unknown;
       }
-      else if ( isDoubleSafe( vL ) && isDoubleSafe( vR ) )
+      else if ( isDoubleSafe( vL ) && isDoubleSafe( vR ) &&
+                ( vL.type() != QVariant::String || vR.type() != QVariant::String ) )
       {
-        // do numeric comparison if both operators can be converted to numbers
+        // do numeric comparison if both operators can be converted to numbers,
+        // and they aren't both string
         double fL = getDoubleValue( vL, parent );
         ENSURE_NO_EVAL_ERROR;
         double fR = getDoubleValue( vR, parent );
@@ -4190,7 +4192,8 @@ QVariant QgsExpression::NodeBinaryOperator::eval( QgsExpression *parent, const Q
       else // both operators non-null
       {
         bool equal = false;
-        if ( isDoubleSafe( vL ) && isDoubleSafe( vR ) )
+        if ( isDoubleSafe( vL ) && isDoubleSafe( vR ) &&
+             ( vL.type() != QVariant::String || vR.type() != QVariant::String ) )
         {
           double fL = getDoubleValue( vL, parent );
           ENSURE_NO_EVAL_ERROR;

tests/src/core/testqgsexpression.cpp

@@ -427,6 +427,20 @@ class TestQgsExpression: public QObject
       QTest::newRow( "'nan'='x'" ) << "'nan'='x'" << false << QVariant( 0 );
       QTest::newRow( "'inf'='inf'" ) << "'inf'='inf'" << false << QVariant( 1 );
       QTest::newRow( "'inf'='x'" ) << "'inf'='x'" << false << QVariant( 0 );
+      QTest::newRow( "'1.1'='1.1'" ) << "'1.1'='1.1'" << false << QVariant( 1 );
+      QTest::newRow( "'1.1'!='1.1'" ) << "'1.1'!='1.1'" << false << QVariant( 0 );
+      QTest::newRow( "'1.1'='1.10'" ) << "'1.1'='1.10'" << false << QVariant( 0 );
+      QTest::newRow( "'1.1'!='1.10'" ) << "'1.1'!='1.10'" << false << QVariant( 1 );
+      QTest::newRow( "1.1=1.10" ) << "1.1=1.10" << false << QVariant( 1 );
+      QTest::newRow( "1.1 != 1.10" ) << "1.1 != 1.10" << false << QVariant( 0 );
+      QTest::newRow( "'1.1'=1.1" ) << "'1.1'=1.1" << false << QVariant( 1 );
+      QTest::newRow( "'1.10'=1.1" ) << "'1.10'=1.1" << false << QVariant( 1 );
+      QTest::newRow( "1.1='1.10'" ) << "1.1='1.10'" << false << QVariant( 1 );
+      QTest::newRow( "'1.1'='1.10000'" ) << "'1.1'='1.10000'" << false << QVariant( 0 );
+      QTest::newRow( "'1E-23'='1E-23'" ) << "'1E-23'='1E-23'" << false << QVariant( 1 );
+      QTest::newRow( "'1E-23'!='1E-23'" ) << "'1E-23'!='1E-23'" << false << QVariant( 0 );
+      QTest::newRow( "'1E-23'='2E-23'" ) << "'1E-23'='2E-23'" << false << QVariant( 0 );
+      QTest::newRow( "'1E-23'!='2E-23'" ) << "'1E-23'!='2E-23'" << false << QVariant( 1 );
 
       // is, is not
       QTest::newRow( "is null,null" ) << "null is null" << false << QVariant( 1 );
@@ -437,6 +451,10 @@ class TestQgsExpression: public QObject
       QTest::newRow( "is not int" ) << "1 is not 1" << false << QVariant( 0 );
       QTest::newRow( "is text" ) << "'x' is 'y'" << false << QVariant( 0 );
       QTest::newRow( "is not text" ) << "'x' is not 'y'" << false << QVariant( 1 );
+      QTest::newRow( "'1.1' is '1.10'" ) << "'1.1' is '1.10'" << false << QVariant( 0 );
+      QTest::newRow( "'1.1' is '1.10000'" ) << "'1.1' is '1.10000'" << false << QVariant( 0 );
+      QTest::newRow( "1.1 is '1.10'" ) << "1.1 is '1.10'" << false << QVariant( 1 );
+      QTest::newRow( "'1.10' is 1.1" ) << "'1.10' is 1.1" << false << QVariant( 1 );
 
       //  logical
       QTest::newRow( "T or F" ) << "1=1 or 2=3" << false << QVariant( 1 );