New library lib-exceptions

libraries/CMakeLists.txt

@@ -9,6 +9,7 @@ set( LIBRARIES
    lib-uuid
    lib-components
    lib-basic-ui
+   lib-exceptions
 )
 
 if ( ${_OPT}has_networking )

libraries/lib-exceptions/AudacityException.cpp

@@ -0,0 +1,116 @@
+/*!********************************************************************
+
+  Audacity: A Digital Audio Editor
+
+  @file AudacityException.cpp
+  @brief Implements AudacityException and related
+
+  Paul Licameli
+
+***********************************************************************/
+
+#include "AudacityException.h"
+
+#include <wx/atomic.h>
+
+#include "BasicUI.h"
+
+AudacityException::~AudacityException()
+{
+}
+
+void AudacityException::EnqueueAction(
+   std::exception_ptr pException,
+   std::function<void(AudacityException*)> delayedHandler)
+{
+   BasicUI::CallAfter( [
+      pException = std::move(pException), delayedHandler = std::move(delayedHandler)
+   ] {
+      try {
+         std::rethrow_exception(pException);
+      }
+      catch( AudacityException &e )
+         { delayedHandler( &e ); }
+   } );
+}
+
+wxAtomicInt sOutstandingMessages {};
+
+MessageBoxException::MessageBoxException(
+   ExceptionType exceptionType_, const TranslatableString& caption_)
+    : caption { caption_ }
+    , exceptionType { exceptionType_ }
+{
+   if (!caption.empty())
+      wxAtomicInc( sOutstandingMessages );
+   else
+      // invalidate me
+      moved = true;
+}
+
+// The class needs a copy constructor to be throwable
+// (or will need it, by C++14 rules).  But the copy
+// needs to act like a move constructor.  There must be unique responsibility
+// for each exception thrown to decrease the global count when it is handled.
+MessageBoxException::MessageBoxException( const MessageBoxException& that )
+{
+   caption = that.caption;
+   moved = that.moved;
+   helpUrl = that.helpUrl;
+   exceptionType = that.exceptionType;
+   that.moved = true;
+}
+
+MessageBoxException::~MessageBoxException()
+{
+   if (!moved)
+      // If exceptions are used properly, you should never reach this,
+      // because moved should become true earlier in the object's lifetime.
+      wxAtomicDec( sOutstandingMessages );
+}
+
+SimpleMessageBoxException::~SimpleMessageBoxException()
+{
+}
+
+TranslatableString SimpleMessageBoxException::ErrorMessage() const
+{
+   return message;
+}
+
+// This is meant to be invoked via wxEvtHandler::CallAfter
+void MessageBoxException::DelayedHandlerAction()
+{
+   if (!moved) {
+      // This test prevents accumulation of multiple messages between idle
+      // times of the main even loop.  Only the last queued exception
+      // displays its message.  We assume that multiple messages have a
+      // common cause such as exhaustion of disk space so that the others
+      // give the user no useful added information.
+      
+      using namespace BasicUI;
+      if ( wxAtomicDec( sOutstandingMessages ) == 0 ) {
+         if (exceptionType != ExceptionType::Internal
+             && ErrorHelpUrl().IsEmpty()) {
+            // We show BadEnvironment and BadUserAction in a similar way
+            ShowMessageBox(
+               ErrorMessage(),
+               MessageBoxOptions{}
+                  .Caption(caption.empty() ? DefaultCaption() : caption)
+                  .IconStyle(Icon::Error) );
+         }
+         else {
+            using namespace BasicUI;
+            auto type = exceptionType == ExceptionType::Internal
+               ? ErrorDialogType::ModalErrorReport : ErrorDialogType::ModalError;
+            ShowErrorDialog( {},
+               (caption.empty() ? DefaultCaption() : caption),
+               ErrorMessage(),
+               ErrorHelpUrl(),
+               ErrorDialogOptions{ type } );
+         }
+      }
+
+      moved = true;
+   }
+}

libraries/lib-exceptions/AudacityException.h

@@ -0,0 +1,231 @@
+#ifndef __AUDACITY_EXCEPTION__
+#define __AUDACITY_EXCEPTION__
+
+/*!********************************************************************
+
+ Audacity: A Digital Audio Editor
+
+ @file AudacityException.h
+ @brief Declare abstract class AudacityException, some often-used subclasses, and @ref GuardedCall
+
+ Paul Licameli
+ **********************************************************************/
+
+#include "MemoryX.h"
+#include <exception>
+#include <functional>
+
+#include "Internat.h"
+
+//! A type of an exception
+enum class ExceptionType
+{
+    Internal, //!< Indicates internal failure from Audacity.
+    BadUserAction, //!< Indicates that the user performed an action that is not allowed.
+    BadEnvironment, //!< Indicates problems with environment, such as a full disk
+};
+
+//! Base class for exceptions specially processed by the application
+/*! Objects of this type can be thrown and caught in any thread, stored, and then used by the main
+ thread in later idle time to explain the error condition to the user.
+ */
+class AudacityException /* not final */
+{
+public:
+   AudacityException() {}
+   virtual ~AudacityException() = 0;
+
+   //! Action to do in the main thread at idle time of the event loop.
+   virtual void DelayedHandlerAction() = 0;
+
+   EXCEPTIONS_API static void EnqueueAction(
+      std::exception_ptr pException,
+      std::function<void(AudacityException*)> delayedHandler);
+
+protected:
+   //! Make this protected to prevent slicing copies
+   AudacityException( const AudacityException& ) = default;
+
+   //! Don't allow moves of this class or subclasses
+   // see https://bugzilla.audacityteam.org/show_bug.cgi?id=2442
+   AudacityException( AudacityException&& ) PROHIBITED;
+
+   //! Disallow assignment
+   AudacityException &operator = ( const AudacityException & ) PROHIBITED;
+};
+
+//! Abstract AudacityException subclass displays a message, specified by further subclass
+/*! At most one message will be displayed for each pass through the main event idle loop,
+ no matter how many exceptions were caught. */
+class EXCEPTIONS_API MessageBoxException /* not final */
+   : public AudacityException
+{
+   //! Privatize the inherited function
+   using AudacityException::DelayedHandlerAction;
+
+   //! Do not allow subclasses to change behavior, except by overriding ErrorMessage().
+   void DelayedHandlerAction() final;
+
+protected:
+   //! If default-constructed with empty caption, it makes no message box.
+   explicit MessageBoxException(
+      ExceptionType exceptionType, //!< Exception type
+      const TranslatableString &caption //!< Shown in message box's frame; not the actual message
+   );
+   ~MessageBoxException() override;
+
+   MessageBoxException( const MessageBoxException& );
+
+   //! %Format the error message for this exception.
+   virtual TranslatableString ErrorMessage() const = 0;
+   virtual wxString ErrorHelpUrl() const { return helpUrl; };
+
+private:
+   TranslatableString caption; //!< Stored caption
+   ExceptionType exceptionType; //!< Exception type
+
+   mutable bool moved { false }; //!< Whether @c *this has been the source of a copy
+protected:
+   mutable wxString helpUrl{ "" };
+};
+
+//! A MessageBoxException that shows a given, unvarying string.
+class EXCEPTIONS_API SimpleMessageBoxException /* not final */
+   : public MessageBoxException
+{
+public:
+   explicit SimpleMessageBoxException(
+      ExceptionType exceptionType,        //!< Exception type
+      const TranslatableString &message_, //<! Message to show
+      const TranslatableString &caption = XO("Message"), //<! Short caption in frame around message
+      const wxString &helpUrl_ = "" // Optional URL for help.
+   )
+      : MessageBoxException { exceptionType, caption }
+      , message{ message_ }
+   {
+      helpUrl = helpUrl_;
+   }
+   ~SimpleMessageBoxException() override;
+
+   SimpleMessageBoxException( const SimpleMessageBoxException& ) = default;
+   SimpleMessageBoxException &operator = (
+      SimpleMessageBoxException && ) PROHIBITED;
+
+   // Format a default, internationalized error message for this exception.
+   virtual TranslatableString ErrorMessage() const override;
+
+private:
+   TranslatableString message; //!< Stored message
+};
+
+
+//! A default template parameter for @ref GuardedCall
+struct DefaultDelayedHandlerAction
+{
+   void operator () (AudacityException *pException) const
+   {
+      if ( pException )
+         pException->DelayedHandlerAction();
+   }
+};
+
+//! A default template parameter for @ref GuardedCall<R>
+/*! @tparam R return type from GuardedCall (or convertible to it) */
+template <typename R> struct SimpleGuard
+{
+   explicit SimpleGuard(
+      R value //!< The value to return from GurdedCall when an exception is handled
+   )
+      : m_value{ value } {}
+   R operator () ( AudacityException * ) const { return m_value; }
+   const R m_value;
+};
+
+//! Specialization of SimpleGuard, also defining a default value
+template<> struct SimpleGuard<bool>
+{
+   explicit SimpleGuard(
+      bool value //!< The value to return from @ref GaurdedCall when an exception is handled
+   )
+      : m_value{ value } {}
+   bool operator () ( AudacityException * ) const { return m_value; }
+   static SimpleGuard Default()
+      { return SimpleGuard{ false }; }
+   const bool m_value;
+};
+
+//! Specialization of SimpleGuard, also defining a default value
+template<> struct SimpleGuard<void>
+{
+   SimpleGuard() {}
+   void operator () ( AudacityException * ) const {}
+   static SimpleGuard Default() { return {}; }
+};
+
+//! Convert a value to a handler function returning that value, suitable for @ref GuardedCall<R>
+template < typename R >
+SimpleGuard< R > MakeSimpleGuard( R value )
+{ return SimpleGuard< R >{ value }; }
+
+//! Convert a value to a no-op handler function, suitable for @ref GuardedCall<void>
+inline SimpleGuard< void > MakeSimpleGuard() { return {}; }
+
+/*!
+  Executes a given function (typically a lamba), in any thread.
+ 
+  If there is any exception, can invoke another given function as handler, which may rethrow that or
+  another exception, but usually just returns the value for the GuardedCall.
+ 
+  If AudacityException is handled, then it queues up a delayed handler action for execution later in
+  the event loop at idle time, on the main thread; typically this informs the user of the error.
+
+  The default delayed handler action is simply to invoke a method of the AudacityException, but this
+  too can be specified otherwise by a third function.
+
+  @tparam R Return type, defaulted to void, or else the only explicit template parameter
+  @tparam F1 deduced type of body function; takes no arguments, returns @b R
+  @tparam F2 deduced type of handler function, or defaulted to @ref SimpleGuard<R>;
+  takes pointer to AudacityException, which is null when some other type of exception is caught;
+  return value is converted to @b R
+  @tparam F3 deduced type of delayed handler function, if a nondefault argument is given;
+  takes pointer to AudacityException, return value is unused
+ */
+template <
+   typename R = void,
+
+   typename F1, // function object with signature R()
+
+   typename F2 = SimpleGuard< R > // function object
+      // with signature R( AudacityException * )
+>
+//! Execute some code on any thread; catch any AudacityException; enqueue error report on the main thread
+R GuardedCall(
+   const F1 &body, //!< typically a lambda
+   const F2 &handler = F2::Default(), //!< default just returns false or void; see also @ref MakeSimpleGuard
+   std::function<void(AudacityException*)> delayedHandler
+      = DefaultDelayedHandlerAction{} /*!<called later in the main thread,
+                                       passing it a stored exception; usually defaulted */
+)
+{
+   try { return body(); }
+   catch ( AudacityException &e ) {
+
+      auto end = finally([&]{
+         // At this point, e is the "current" exception, but not "uncaught"
+         // unless it was rethrown by handler.  handler might also throw some
+         // other exception object.
+         if (!std::uncaught_exception()) {
+            auto pException = std::current_exception(); // This points to e
+            AudacityException::EnqueueAction(
+               pException, std::move(delayedHandler));
+         }
+      });
+
+      return handler( &e );
+   }
+   catch ( ... ) {
+      return handler( nullptr );
+   }
+}
+
+#endif

libraries/lib-exceptions/CMakeLists.txt

@@ -0,0 +1,34 @@
+#[[
+Toolkit neutral library for exceptions.
+
+Abstract class AudacityException with a member function for a delayed
+handler action, enqueued in the main thread;
+
+Some commonly useful subclasses, with delayed handlers that are no-ops or
+are displays of messages to the user;
+
+Function template GuardedCall which stops propagation of exceptions and
+enqueues the delayed action.
+
+But this library does NOT define a top-level handler for the whole application,
+to catch all otherwise uncaught exceptions. That is a responsibility of high
+level code.
+]]#
+
+list( APPEND SOURCES
+   AudacityException.cpp
+   AudacityException.h
+   InconsistencyException.cpp
+   InconsistencyException.h
+   UserException.cpp
+   UserException.h
+)
+set( LIBRARIES
+   lib-utility-interface
+   lib-basic-ui-interface
+   PRIVATE
+   wxBase
+)
+audacity_library( lib-exceptions "${SOURCES}" "${LIBRARIES}"
+   "" ""
+)

libraries/lib-exceptions/InconsistencyException.cpp

@@ -0,0 +1,35 @@
+/*!
+  @file InconsistencyException.cpp
+  @brief Implements InconsistencyException
+  
+
+  Created by Paul Licameli on 11/27/16.
+
+*/
+
+#include "InconsistencyException.h"
+#include <wx/filename.h>
+
+InconsistencyException::~InconsistencyException()
+{
+}
+
+TranslatableString InconsistencyException::ErrorMessage() const
+{
+   // Shorten the path
+   wxString path { file };
+   auto sub = wxString{ wxFILE_SEP_PATH } + "src" + wxFILE_SEP_PATH;
+   auto index = path.Find(sub);
+   if (index != wxNOT_FOUND)
+      path = path.Mid(index + sub.size());
+
+#ifdef __func__
+   return
+XO("Internal error in %s at %s line %d.\nPlease inform the Audacity team at https://forum.audacityteam.org/.")
+      .Format( func, path, line );
+#else
+   return
+XO("Internal error at %s line %d.\nPlease inform the Audacity team at https://forum.audacityteam.org/.")
+      .Format( path, line );
+#endif
+}

libraries/lib-exceptions/InconsistencyException.h

@@ -0,0 +1,81 @@
+/*!
+  @file InconsistencyException.h
+  @brief MessageBoxException for violation of preconditions or assertions
+
+  Created by Paul Licameli on 11/27/16.
+
+*/
+
+#ifndef __AUDACITY_INCONSISTENCY_EXCEPTION__
+#define __AUDACITY_INCONSISTENCY_EXCEPTION__
+
+#include "AudacityException.h"
+
+//! Exception that should be impossible in production, thrown only from provably unreachable places
+/*!  Some errors that formerly were assertion violations now throw exceptions,
+  even in production code.  These may be violations of function preconditions
+  or the results of logical errors internal to functions.  These conditions
+  are supposed to be deducible statically as never happening.
+ 
+  The error message identifies source file and line number, possibly the function too (depending on
+  the compiler), and suggests that the user inform the development team.
+ */
+class EXCEPTIONS_API InconsistencyException final : public MessageBoxException
+{
+public:
+   InconsistencyException () 
+       : MessageBoxException{ ExceptionType::Internal, XO ("Internal Error") } 
+   {}
+
+   //! Don't call this directly but use @ref CONSTRUCT_INCONSISTENCY_EXCEPTION or @ref THROW_INCONSISTENCY_EXCEPTION
+   explicit InconsistencyException(
+      const char *fn, //!< file name supplied by preprocessor
+      const char *f, //!< function name supplied by preprocessor
+      unsigned l //!< line number supplied by preprocessor
+   )
+       : MessageBoxException { ExceptionType::Internal, XO("Internal Error") }
+       , func { fn }, file { f }, line { l }
+   {}
+
+   InconsistencyException(InconsistencyException&& that)
+      : MessageBoxException(std::move(that))
+      , func{ that.func }
+      , file{ that.file }
+      , line{ that.line }
+   {}
+
+   ~InconsistencyException() override;
+
+   unsigned GetLine() const { return line; }
+
+private:
+   // Format a default, internationalized error message for this exception.
+   TranslatableString ErrorMessage() const override;
+
+   const char *func {};
+   const char *file {};
+   unsigned line {};
+};
+
+#ifdef __func__
+
+#define CONSTRUCT_INCONSISTENCY_EXCEPTION \
+   InconsistencyException( __func__, __FILE__ , __LINE__ )
+
+#else
+
+/*! @def CONSTRUCT_INCONSISTENCY_EXCEPTION
+@brief Construct InconsistencyException, using C++ preprocessor to identify the source code location
+
+For cases where the exception object is not immediately thrown */
+#define CONSTRUCT_INCONSISTENCY_EXCEPTION \
+   InconsistencyException( "", __FILE__ , __LINE__ )
+
+#endif
+
+/*! @def THROW_INCONSISTENCY_EXCEPTION
+@brief Throw InconsistencyException, using C++ preprocessor to identify the source code location
+*/
+#define THROW_INCONSISTENCY_EXCEPTION throw CONSTRUCT_INCONSISTENCY_EXCEPTION
+
+#endif

libraries/lib-exceptions/UserException.cpp

@@ -0,0 +1,17 @@
+/*!
+  @file UserException.cpp
+  @brief implements UserException
+
+  Created by Paul Licameli on 11/27/16.
+
+*/
+
+#include "UserException.h"
+
+UserException::~UserException()
+{
+}
+
+void UserException::DelayedHandlerAction()
+{
+}

libraries/lib-exceptions/UserException.h

@@ -0,0 +1,26 @@
+/*!
+ @file UserException.h
+ @brief An AudacityException with no visible message
+
+ Created by Paul Licameli on 11/27/16.
+
+*/
+
+#ifndef __AUDACITY_USER_EXCEPTION__
+#define __AUDACITY_USER_EXCEPTION__
+
+#include "AudacityException.h"
+
+ //! Can be thrown when user cancels operations, as with a progress dialog.  Delayed handler does nothing
+/*! This class does not inherit from MessageBoxException. */
+class EXCEPTIONS_API UserException final : public AudacityException
+{
+public:
+   UserException() {}
+
+   ~UserException() override;
+
+   void DelayedHandlerAction() override;
+};
+
+#endif