BREAKING: Check MATLAB exceptions

src/MATLAB.jl

@@ -43,11 +43,7 @@ else
     )
 end
 
-# exceptions
-struct MEngineError <: Exception
-    message::String
-end
-
+include("exceptions.jl")
 include("init.jl") # initialize Refs
 include("mxarray.jl")
 include("matfile.jl")

src/engine.jl

@@ -20,8 +20,13 @@ mutable struct MSession
     ptr::Ptr{Cvoid}
     buffer::Vector{UInt8}
     bufptr::Ptr{UInt8}
+    check_exceptions::Bool
 
-    function MSession(bufsize::Integer=default_output_buffer_size; flags=default_startflag)
+    function MSession(
+        bufsize::Integer=default_output_buffer_size;
+        flags=default_startflag,
+        check_exceptions::Bool=true,
+    )
         if Sys.iswindows()
             assign_persistent_msession()
         end
@@ -56,7 +61,7 @@ mutable struct MSession
             bufptr = convert(Ptr{UInt8}, C_NULL)
         end
 
-        self = new(ep, buf, bufptr)
+        self = new(ep, buf, bufptr, check_exceptions)
         finalizer(release, self)
         return self
     end
@@ -85,6 +90,13 @@ function close(session::MSession)
     return nothing
 end
 
+has_exception_check_enabled(session::MSession=get_default_msession()) =
+    session.check_exceptions
+disable_exception_check!(session::MSession=get_default_msession()) =
+    (session.check_exceptions = false; nothing)
+enable_exception_check!(session::MSession=get_default_msession()) =
+    (session.check_exceptions = true; nothing)
+
 # default session
 
 const default_msession_ref = Ref{MSession}()
@@ -137,7 +149,7 @@ end
 #
 ###########################################################
 
-function eval_string(session::MSession, stmt::String)
+function _eval_string(session::MSession, stmt::String)
     # evaluate a MATLAB statement in a given MATLAB session
     ret = ccall(eng_eval_string[], Cint, (Ptr{Cvoid}, Ptr{UInt8}), session, stmt)
     ret != 0 && throw(MEngineError("invalid engine session (err = $ret)"))
@@ -152,6 +164,13 @@ function eval_string(session::MSession, stmt::String)
     return nothing
 end
 
+function eval_string(session::MSession, stmt::String)
+    _eval_string(session, stmt)
+    if session.check_exceptions
+        check_and_clear_last_exception(session)
+    end
+end
+
 eval_string(stmt::String) = eval_string(get_default_msession(), stmt)
 
 function put_variable(session::MSession, name::Symbol, v::MxArray)
@@ -192,6 +211,33 @@ get_mvariable(name::Symbol) = get_mvariable(get_default_msession(), name)
 get_variable(name::Symbol) = jvalue(get_mvariable(name))
 get_variable(name::Symbol, kind) = jvalue(get_mvariable(name), kind)
 
+"""
+    check_and_clear_last_exception(session::MSession)
+
+Checks if an exception has been thrown in the MATLAB session by checking the `MException.last` variable.
+If it is not empty, it throws a `MatlabException` with the message and identifier of the last exception.
+In any case, it clears the `MException.last` variable.
+"""
+function check_and_clear_last_exception(session::MSession)
+    exception_check_code = """
+    matlab_exception_jl_message = MException.last.message; 
+    matlab_exception_jl_identifier = MException.last.identifier; 
+    MException.last('reset');
+    """
+    _eval_string(session, exception_check_code)
+    message = jvalue(get_mvariable(session, :matlab_exception_jl_message))
+    identifier = jvalue(get_mvariable(session, :matlab_exception_jl_identifier))
+
+    if !isempty(identifier)
+        throw(MatlabException(identifier, message))
+    end
+
+    _eval_string(
+        session,
+        "clear matlab_exception_jl_message matlab_exception_jl_identifier;",
+    )
+end
+
 ###########################################################
 #
 #   macro to simplify syntax

src/exceptions.jl

@@ -0,0 +1,14 @@
+struct MEngineError <: Exception
+    message::String
+end
+
+"""
+    MEngineError(message::String)
+
+Exception thrown by MATLAB, e.g. due to syntax errors in the code
+passed to `eval_string` or `mat"..."`.
+"""
+struct MatlabException <: Exception
+    identifier::String
+    message::String
+end

test/matstr.jl

@@ -70,3 +70,33 @@ $d ...
 # Test strings with =
 text = "hello = world"
 @test mat"strfind($text, 'o = w')" == 5
+
+@testset "Propagate Matlab Exceptions" begin
+
+    # Checks should be enabled by default
+    @test MATLAB.has_exception_check_enabled() == true
+
+    # Test invalid command
+    @test_throws MATLAB.MatlabException mat"invalid_command"
+
+    # Test invalid assignment
+    @test_throws MATLAB.MatlabException mat"1 = 2"
+
+    # Test invalid command within a block
+    @test_throws MATLAB.MatlabException mat"""
+    xyz = 1 + 2;
+    invalid_command;
+    abc = 2 * xyz;
+    """
+
+    # Disable Checks
+    MATLAB.disable_exception_check!()
+    @test MATLAB.has_exception_check_enabled() == false
+
+    # Test invalid command
+    try
+        mat"invalid_command"
+    catch ex
+        @test false # should not throw an exception
+    end
+end