lazily stringify expressions

include/internal/catch_assertionresult.h

@@ -13,6 +13,27 @@
 
 namespace Catch {
 
+    struct STATIC_ASSERT_Expression_Too_Complex_Please_Rewrite_As_Binary_Comparison;
+
+    struct DecomposedExpression
+    {
+        virtual ~DecomposedExpression() {}
+        virtual bool isBinaryExpression() const {
+            return false;
+        }
+        virtual void reconstructExpression( std::string& dest ) const = 0;
+
+        // Only simple binary comparisons can be decomposed.
+        // If more complex check is required then wrap sub-expressions in parentheses.
+        template<typename T> STATIC_ASSERT_Expression_Too_Complex_Please_Rewrite_As_Binary_Comparison& operator + ( T const& );
+        template<typename T> STATIC_ASSERT_Expression_Too_Complex_Please_Rewrite_As_Binary_Comparison& operator - ( T const& );
+        template<typename T> STATIC_ASSERT_Expression_Too_Complex_Please_Rewrite_As_Binary_Comparison& operator * ( T const& );
+        template<typename T> STATIC_ASSERT_Expression_Too_Complex_Please_Rewrite_As_Binary_Comparison& operator / ( T const& );
+        template<typename T> STATIC_ASSERT_Expression_Too_Complex_Please_Rewrite_As_Binary_Comparison& operator % ( T const& );
+        template<typename T> STATIC_ASSERT_Expression_Too_Complex_Please_Rewrite_As_Binary_Comparison& operator && ( T const& );
+        template<typename T> STATIC_ASSERT_Expression_Too_Complex_Please_Rewrite_As_Binary_Comparison& operator || ( T const& );
+    };
+
     struct AssertionInfo
     {
         AssertionInfo() {}
@@ -29,11 +50,41 @@ namespace Catch {
 
     struct AssertionResultData
     {
-        AssertionResultData() : resultType( ResultWas::Unknown ) {}
+        AssertionResultData() : decomposedExpression( CATCH_NULL )
+                              , resultType( ResultWas::Unknown )
+                              , negated( false )
+                              , parenthesized( false ) {}
 
-        std::string reconstructedExpression;
+        void negate( bool parenthesize ) {
+            negated = !negated;
+            parenthesized = parenthesize;
+            if( resultType == ResultWas::Ok )
+                resultType = ResultWas::ExpressionFailed;
+            else if( resultType == ResultWas::ExpressionFailed )
+                resultType = ResultWas::Ok;
+        }
+
+        std::string const& reconstructExpression() const {
+            if( decomposedExpression != CATCH_NULL ) {
+                decomposedExpression->reconstructExpression( reconstructedExpression );
+                if( parenthesized ) {
+                    reconstructedExpression.insert( 0, 1, '(' );
+                    reconstructedExpression.append( 1, ')' );
+                }
+                if( negated ) {
+                    reconstructedExpression.insert( 0, 1, '!' );
+                }
+                decomposedExpression = CATCH_NULL;
+            }
+            return reconstructedExpression;
+        }
+
+        mutable DecomposedExpression const* decomposedExpression;
+        mutable std::string reconstructedExpression;
         std::string message;
         ResultWas::OfType resultType;
+        bool negated;
+        bool parenthesized;
     };
 
     class AssertionResult {
@@ -60,6 +111,8 @@ namespace Catch {
         std::string getMessage() const;
         SourceLineInfo getSourceInfo() const;
         std::string getTestMacroName() const;
+        void discardDecomposedExpression() const;
+        void expandDecomposedExpression() const;
 
     protected:
         AssertionInfo m_info;

include/internal/catch_assertionresult.hpp

@@ -72,7 +72,7 @@ namespace Catch {
     }
 
     std::string AssertionResult::getExpandedExpression() const {
-        return m_resultData.reconstructedExpression;
+        return m_resultData.reconstructExpression();
     }
 
     std::string AssertionResult::getMessage() const {
@@ -86,6 +86,14 @@ namespace Catch {
         return m_info.macroName;
     }
 
+    void AssertionResult::discardDecomposedExpression() const {
+        m_resultData.decomposedExpression = CATCH_NULL;
+    }
+
+    void AssertionResult::expandDecomposedExpression() const {
+        m_resultData.reconstructExpression();
+    }
+
 } // end namespace Catch
 
 #endif // TWOBLUECUBES_CATCH_ASSERTIONRESULT_HPP_INCLUDED

include/internal/catch_capture.hpp

@@ -132,13 +132,7 @@
     do { \
         Catch::ResultBuilder __catchResult( macroName, CATCH_INTERNAL_LINEINFO, #arg ", " #matcher, resultDisposition ); \
         try { \
-            std::string matcherAsString = (matcher).toString(); \
+            __catchResult.captureMatch( arg, matcher, #matcher ); \
-            __catchResult \
-                .setLhs( Catch::toString( arg ) ) \
-                .setRhs( matcherAsString == Catch::Detail::unprintableString ? #matcher : matcherAsString ) \
-                .setOp( "matches" ) \
-                .setResultType( (matcher).match( arg ) ); \
-            __catchResult.captureExpression(); \
         } catch( ... ) { \
             __catchResult.useActiveException( resultDisposition | Catch::ResultDisposition::ContinueOnFailure ); \
         } \

include/internal/catch_expression_lhs.hpp

@@ -14,90 +14,155 @@
 
 namespace Catch {
 
-// Wraps the LHS of an expression and captures the operator and RHS (if any) -
+template<typename LhsT, Internal::Operator Op, typename RhsT>
-// wrapping them all in a ResultBuilder object
+class BinaryExpression;
-template<typename T>
-class ExpressionLhs {
-    ExpressionLhs& operator = ( ExpressionLhs const& );
-#  ifdef CATCH_CONFIG_CPP11_GENERATED_METHODS
-    ExpressionLhs& operator = ( ExpressionLhs && ) = delete;
-#  endif
 
+template<typename ArgT, typename MatcherT>
+class MatchExpression;
+
+// Wraps the LHS of an expression and overloads comparison operators
+// for also capturing those and RHS (if any)
+template<typename T>
+class ExpressionLhs : public DecomposedExpression {
 public:
-    ExpressionLhs( ResultBuilder& rb, T lhs ) : m_rb( rb ), m_lhs( lhs ) {}
+    ExpressionLhs( ResultBuilder& rb, T lhs ) : m_rb( rb ), m_lhs( lhs ), m_truthy(false) {}
-#  ifdef CATCH_CONFIG_CPP11_GENERATED_METHODS
-    ExpressionLhs( ExpressionLhs const& ) = default;
-    ExpressionLhs( ExpressionLhs && )     = default;
-#  endif
 
     template<typename RhsT>
-    ResultBuilder& operator == ( RhsT const& rhs ) {
+    BinaryExpression<T, Internal::IsEqualTo, RhsT const&>
+    operator == ( RhsT const& rhs ) const {
         return captureExpression<Internal::IsEqualTo>( rhs );
     }
 
     template<typename RhsT>
-    ResultBuilder& operator != ( RhsT const& rhs ) {
+    BinaryExpression<T, Internal::IsNotEqualTo, RhsT const&>
+    operator != ( RhsT const& rhs ) const {
         return captureExpression<Internal::IsNotEqualTo>( rhs );
     }
 
     template<typename RhsT>
-    ResultBuilder& operator < ( RhsT const& rhs ) {
+    BinaryExpression<T, Internal::IsLessThan, RhsT const&>
+    operator < ( RhsT const& rhs ) const {
         return captureExpression<Internal::IsLessThan>( rhs );
     }
 
     template<typename RhsT>
-    ResultBuilder& operator > ( RhsT const& rhs ) {
+    BinaryExpression<T, Internal::IsGreaterThan, RhsT const&>
+    operator > ( RhsT const& rhs ) const {
         return captureExpression<Internal::IsGreaterThan>( rhs );
     }
 
     template<typename RhsT>
-    ResultBuilder& operator <= ( RhsT const& rhs ) {
+    BinaryExpression<T, Internal::IsLessThanOrEqualTo, RhsT const&>
+    operator <= ( RhsT const& rhs ) const {
         return captureExpression<Internal::IsLessThanOrEqualTo>( rhs );
     }
 
     template<typename RhsT>
-    ResultBuilder& operator >= ( RhsT const& rhs ) {
+    BinaryExpression<T, Internal::IsGreaterThanOrEqualTo, RhsT const&>
+    operator >= ( RhsT const& rhs ) const {
         return captureExpression<Internal::IsGreaterThanOrEqualTo>( rhs );
     }
 
-    ResultBuilder& operator == ( bool rhs ) {
+    BinaryExpression<T, Internal::IsEqualTo, bool> operator == ( bool rhs ) const {
         return captureExpression<Internal::IsEqualTo>( rhs );
     }
 
-    ResultBuilder& operator != ( bool rhs ) {
+    BinaryExpression<T, Internal::IsNotEqualTo, bool> operator != ( bool rhs ) const {
         return captureExpression<Internal::IsNotEqualTo>( rhs );
     }
 
     void endExpression() {
-        bool value = m_lhs ? true : false;
+        m_truthy = m_lhs ? true : false;
         m_rb
-            .setLhs( Catch::toString( value ) )
+            .setResultType( m_truthy )
-            .setResultType( value )
+            .endExpression( *this );
-            .endExpression();
     }
 
-    // Only simple binary expressions are allowed on the LHS.
+    virtual void reconstructExpression( std::string& dest ) const CATCH_OVERRIDE {
-    // If more complex compositions are required then place the sub expression in parentheses
+        dest = Catch::toString( m_truthy );
-    template<typename RhsT> STATIC_ASSERT_Expression_Too_Complex_Please_Rewrite_As_Binary_Comparison& operator + ( RhsT const& );
+    }
-    template<typename RhsT> STATIC_ASSERT_Expression_Too_Complex_Please_Rewrite_As_Binary_Comparison& operator - ( RhsT const& );
-    template<typename RhsT> STATIC_ASSERT_Expression_Too_Complex_Please_Rewrite_As_Binary_Comparison& operator / ( RhsT const& );
-    template<typename RhsT> STATIC_ASSERT_Expression_Too_Complex_Please_Rewrite_As_Binary_Comparison& operator * ( RhsT const& );
-    template<typename RhsT> STATIC_ASSERT_Expression_Too_Complex_Please_Rewrite_As_Binary_Comparison& operator && ( RhsT const& );
-    template<typename RhsT> STATIC_ASSERT_Expression_Too_Complex_Please_Rewrite_As_Binary_Comparison& operator || ( RhsT const& );
 
 private:
     template<Internal::Operator Op, typename RhsT>
-    ResultBuilder& captureExpression( RhsT const& rhs ) {
+    BinaryExpression<T, Op, RhsT&> captureExpression( RhsT& rhs ) const {
-        return m_rb
+        return BinaryExpression<T, Op, RhsT&>( m_rb, m_lhs, rhs );
-            .setResultType( Internal::compare<Op>( m_lhs, rhs ) )
+    }
-            .setLhs( Catch::toString( m_lhs ) )
+
-            .setRhs( Catch::toString( rhs ) )
+    template<Internal::Operator Op>
-            .setOp( Internal::OperatorTraits<Op>::getName() );
+    BinaryExpression<T, Op, bool> captureExpression( bool rhs ) const {
+        return BinaryExpression<T, Op, bool>( m_rb, m_lhs, rhs );
     }
 
 private:
     ResultBuilder& m_rb;
     T m_lhs;
+    bool m_truthy;
+};
+
+template<typename LhsT, Internal::Operator Op, typename RhsT>
+class BinaryExpression : public DecomposedExpression {
+public:
+    BinaryExpression( ResultBuilder& rb, LhsT lhs, RhsT rhs )
+        : m_rb( rb ), m_lhs( lhs ), m_rhs( rhs ) {}
+
+    void endExpression() const {
+        m_rb
+            .setResultType( Internal::compare<Op>( m_lhs, m_rhs ) )
+            .endExpression( *this );
+    }
+
+    virtual bool isBinaryExpression() const CATCH_OVERRIDE {
+        return true;
+    }
+
+    virtual void reconstructExpression( std::string& dest ) const CATCH_OVERRIDE {
+        std::string lhs = Catch::toString( m_lhs );
+        std::string rhs = Catch::toString( m_rhs );
+        char delim = lhs.size() + rhs.size() < 40 &&
+                     lhs.find('\n') == std::string::npos &&
+                     rhs.find('\n') == std::string::npos ? ' ' : '\n';
+        dest.reserve( 7 + lhs.size() + rhs.size() );
+                   // 2 for spaces around operator
+                   // 2 for operator
+                   // 2 for parentheses (conditionally added later)
+                   // 1 for negation (conditionally added later)
+        dest = lhs;
+        dest += delim;
+        dest += Internal::OperatorTraits<Op>::getName();
+        dest += delim;
+        dest += rhs;
+    }
+
+private:
+    ResultBuilder& m_rb;
+    LhsT m_lhs;
+    RhsT m_rhs;
+};
+
+template<typename ArgT, typename MatcherT>
+class MatchExpression : public DecomposedExpression {
+public:
+    MatchExpression( ArgT arg, MatcherT matcher, char const* matcherString )
+        : m_arg( arg ), m_matcher( matcher ), m_matcherString( matcherString ) {}
+
+    virtual bool isBinaryExpression() const CATCH_OVERRIDE {
+        return true;
+    }
+
+    virtual void reconstructExpression( std::string& dest ) const CATCH_OVERRIDE {
+        std::string matcherAsString = m_matcher.toString();
+        dest = Catch::toString( m_arg );
+        dest += ' ';
+        if( matcherAsString == Detail::unprintableString )
+            dest += m_matcherString;
+        else
+            dest += matcherAsString;
+    }
+
+private:
+    ArgT m_arg;
+    MatcherT m_matcher;
+    char const* m_matcherString;
 };
 
 } // end namespace Catch

include/internal/catch_result_builder.h

@@ -19,8 +19,6 @@ namespace Catch {
 
     template<typename T> class ExpressionLhs;
 
-    struct STATIC_ASSERT_Expression_Too_Complex_Please_Rewrite_As_Binary_Comparison;
-
     struct CopyableStream {
         CopyableStream() {}
         CopyableStream( CopyableStream const& other ) {
@@ -34,7 +32,7 @@ namespace Catch {
         std::ostringstream oss;
     };
 
-    class ResultBuilder {
+    class ResultBuilder : public DecomposedExpression {
     public:
         ResultBuilder(  char const* macroName,
                         SourceLineInfo const& lineInfo,
@@ -52,19 +50,15 @@ namespace Catch {
             return *this;
         }
 
-        template<typename RhsT> STATIC_ASSERT_Expression_Too_Complex_Please_Rewrite_As_Binary_Comparison& operator && ( RhsT const& );
-        template<typename RhsT> STATIC_ASSERT_Expression_Too_Complex_Please_Rewrite_As_Binary_Comparison& operator || ( RhsT const& );
-
         ResultBuilder& setResultType( ResultWas::OfType result );
         ResultBuilder& setResultType( bool result );
-        ResultBuilder& setLhs( std::string const& lhs );
-        ResultBuilder& setRhs( std::string const& rhs );
-        ResultBuilder& setOp( std::string const& op );
 
-        void endExpression();
+        void endExpression( DecomposedExpression const& expr );
+
+        virtual void reconstructExpression( std::string& dest ) const CATCH_OVERRIDE;
 
-        std::string reconstructExpression() const;
         AssertionResult build() const;
+        AssertionResult build( DecomposedExpression const& expr ) const;
 
         void useActiveException( ResultDisposition::Flags resultDisposition = ResultDisposition::Normal );
         void captureResult( ResultWas::OfType resultType );
@@ -76,14 +70,12 @@ namespace Catch {
         bool shouldDebugBreak() const;
         bool allowThrows() const;
 
+        template<typename ArgT, typename MatcherT>
+        void captureMatch( ArgT const& arg, MatcherT const& matcher, char const* matcherString );
+
     private:
         AssertionInfo m_assertionInfo;
         AssertionResultData m_data;
-        struct ExprComponents {
-            ExprComponents() : testFalse( false ) {}
-            bool testFalse;
-            std::string lhs, rhs, op;
-        } m_exprComponents;
         CopyableStream m_stream;
 
         bool m_shouldDebugBreak;
@@ -106,6 +98,14 @@ namespace Catch {
         return ExpressionLhs<bool>( *this, value );
     }
 
+    template<typename ArgT, typename MatcherT>
+    inline void ResultBuilder::captureMatch( ArgT const& arg, MatcherT const& matcher,
+                                             char const* matcherString ) {
+        MatchExpression<ArgT const&, MatcherT const&> expr( arg, matcher, matcherString );
+        setResultType( matcher.match( arg ) );
+        endExpression( expr );
+    }
+
 } // namespace Catch
 
 #endif // TWOBLUECUBES_CATCH_RESULT_BUILDER_H_INCLUDED

include/internal/catch_result_builder.hpp

@@ -41,22 +41,10 @@ namespace Catch {
         m_data.resultType = result ? ResultWas::Ok : ResultWas::ExpressionFailed;
         return *this;
     }
-    ResultBuilder& ResultBuilder::setLhs( std::string const& lhs ) {
-        m_exprComponents.lhs = lhs;
-        return *this;
-    }
-    ResultBuilder& ResultBuilder::setRhs( std::string const& rhs ) {
-        m_exprComponents.rhs = rhs;
-        return *this;
-    }
-    ResultBuilder& ResultBuilder::setOp( std::string const& op ) {
-        m_exprComponents.op = op;
-        return *this;
-    }
 
-    void ResultBuilder::endExpression() {
+    void ResultBuilder::endExpression( DecomposedExpression const& expr ) {
-        m_exprComponents.testFalse = isFalseTest( m_assertionInfo.resultDisposition );
+        AssertionResult result = build( expr );
-        captureExpression();
+        handleResult( result );
     }
 
     void ResultBuilder::useActiveException( ResultDisposition::Flags resultDisposition ) {
@@ -69,6 +57,7 @@ namespace Catch {
         setResultType( resultType );
         captureExpression();
     }
+
     void ResultBuilder::captureExpectedException( std::string const& expectedMessage ) {
         if( expectedMessage.empty() )
             captureExpectedException( Matchers::Impl::Generic::AllOf<std::string>() );
@@ -78,7 +67,7 @@ namespace Catch {
 
     void ResultBuilder::captureExpectedException( Matchers::Impl::Matcher<std::string> const& matcher ) {
 
-        assert( m_exprComponents.testFalse == false );
+        assert( !isFalseTest( m_assertionInfo.resultDisposition ) );
         AssertionResultData data = m_data;
         data.resultType = ResultWas::Ok;
         data.reconstructedExpression = m_assertionInfo.capturedExpression;
@@ -96,6 +85,7 @@ namespace Catch {
         AssertionResult result = build();
         handleResult( result );
     }
+
     void ResultBuilder::handleResult( AssertionResult const& result )
     {
         getResultCapture().assertionEnded( result );
@@ -107,6 +97,7 @@ namespace Catch {
                 m_shouldThrow = true;
         }
     }
+
     void ResultBuilder::react() {
         if( m_shouldThrow )
             throw Catch::TestFailureException();
@@ -117,43 +108,32 @@ namespace Catch {
 
     AssertionResult ResultBuilder::build() const
     {
-        assert( m_data.resultType != ResultWas::Unknown );
+        return build( *this );
+    }
 
+    // CAVEAT: The returned AssertionResult stores a pointer to the argument expr,
+    //         a temporary DecomposedExpression, which in turn holds references to
+    //         operands, possibly temporary as well.
+    //         It should immediately be passed to handleResult; if the expression
+    //         needs to be reported, its string expansion must be composed before
+    //         the temporaries are destroyed.
+    AssertionResult ResultBuilder::build( DecomposedExpression const& expr ) const
+    {
+        assert( m_data.resultType != ResultWas::Unknown );
         AssertionResultData data = m_data;
 
-        // Flip bool results if testFalse is set
+        // Flip bool results if FalseTest flag is set
-        if( m_exprComponents.testFalse ) {
+        if( isFalseTest( m_assertionInfo.resultDisposition ) ) {
-            if( data.resultType == ResultWas::Ok )
+            data.negate( expr.isBinaryExpression() );
-                data.resultType = ResultWas::ExpressionFailed;
-            else if( data.resultType == ResultWas::ExpressionFailed )
-                data.resultType = ResultWas::Ok;
         }
 
         data.message = m_stream.oss.str();
-        data.reconstructedExpression = reconstructExpression();
+        data.decomposedExpression = &expr; // for lazy reconstruction
-        if( m_exprComponents.testFalse ) {
-            if( m_exprComponents.op == "" )
-                data.reconstructedExpression = "!" + data.reconstructedExpression;
-            else
-                data.reconstructedExpression = "!(" + data.reconstructedExpression + ")";
-        }
         return AssertionResult( m_assertionInfo, data );
     }
-    std::string ResultBuilder::reconstructExpression() const {
+
-        if( m_exprComponents.op == "" )
+    void ResultBuilder::reconstructExpression( std::string& dest ) const {
-            return m_exprComponents.lhs.empty() ? m_assertionInfo.capturedExpression : m_exprComponents.lhs;
+        dest = m_assertionInfo.capturedExpression;
-        else if( m_exprComponents.op == "matches" )
-            return m_exprComponents.lhs + " " + m_exprComponents.rhs;
-        else if( m_exprComponents.op != "!" ) {
-            if( m_exprComponents.lhs.size() + m_exprComponents.rhs.size() < 40 &&
-                m_exprComponents.lhs.find("\n") == std::string::npos &&
-                m_exprComponents.rhs.find("\n") == std::string::npos )
-                return m_exprComponents.lhs + " " + m_exprComponents.op + " " + m_exprComponents.rhs;
-            else
-                return m_exprComponents.lhs + "\n" + m_exprComponents.op + "\n" + m_exprComponents.rhs;
-        }
-        else
-            return "{can't expand - use " + m_assertionInfo.macroName + "_FALSE( " + m_assertionInfo.capturedExpression.substr(1) + " ) instead of " + m_assertionInfo.macroName + "( " + m_assertionInfo.capturedExpression + " ) for better diagnostics}";
     }
 
 } // end namespace Catch

include/reporters/catch_reporter_bases.hpp

@@ -170,6 +170,12 @@ namespace Catch {
             assert( !m_sectionStack.empty() );
             SectionNode& sectionNode = *m_sectionStack.back();
             sectionNode.assertions.push_back( assertionStats );
+            // AssertionResult holds a pointer to a temporary DecomposedExpression,
+            // which getExpandedExpression() calls to build the expression string.
+            // Our section stack copy of the assertionResult will likely outlive the
+            // temporary, so it must be expanded or discarded now to avoid calling
+            // a destroyed object later.
+            prepareExpandedExpression( sectionNode.assertions.back().assertionResult );
             return true;
         }
         virtual void sectionEnded( SectionStats const& sectionStats ) CATCH_OVERRIDE {
@@ -204,6 +210,13 @@ namespace Catch {
 
         virtual void skipTest( TestCaseInfo const& ) CATCH_OVERRIDE {}
 
+        virtual void prepareExpandedExpression( AssertionResult& result ) const {
+            if( result.isOk() )
+                result.discardDecomposedExpression();
+            else
+                result.expandDecomposedExpression();
+        }
+
         Ptr<IConfig const> m_config;
         std::ostream& stream;
         std::vector<AssertionStats> m_assertions;