src/samples/trycatch_test.mlua

   1 -{ extension 'trycatch' }
   2
   3
   4 ----------------------------------------------------------------------
   5 print "1) no error"
   6 try
   7    print("   Hi")
   8 end
   9
  10
  11 ----------------------------------------------------------------------
  12 print "2) caught error"
  13 try
  14    error "some_error"
  15 catch x ->
  16    printf("   Successfully caught %q", x)
  17 end
  18
  19
  20 ----------------------------------------------------------------------
  21 print "3) no error, with a finally"
  22 try
  23    print "   Hi"
  24 finally
  25    print "   Finally OK"
  26 end
  27
  28
  29 ----------------------------------------------------------------------
  30 print "4) error, with a finally"
  31 try
  32    print "   Hi"
  33    error "bang"
  34 catch "bang" ->
  35    -- nothing
  36 finally
  37    print "   Finally OK"
  38 end
  39
  40
  41 ----------------------------------------------------------------------
  42 print "5) nested catchers"
  43 try
  44    try
  45       error "some_error"
  46    catch "some_other_error" ->
  47       assert (false, "mismatch, this must not happen")
  48    end
  49 catch "some_error"/x ->
  50    printf("   Successfully caught %q across a try that didn't catch", x)
  51 | x ->
  52    assert (false, "We shouldn't reach this catch-all")
  53 end
  54
  55
  56 ----------------------------------------------------------------------
  57 print "6) nested catchers, with a 'finally in the inner one"
  58 try
  59    try
  60       error "some_error"
  61    catch "some_other_error" ->
  62       assert (false, "mismatch, this must not happen")
  63    finally
  64       print "   Leaving the inner try-catch"
  65    end
  66 catch "some_error"/x ->
  67    printf("   Successfully caught %q across a try that didn't catch", x)
  68 | x ->
  69    assert (false, "We shouldn't reach this catch-all")
  70 end
  71
  72
  73 ----------------------------------------------------------------------
  74 print "7) 'finally' intercepts a return from a function"
  75 function f()
  76    try
  77       print "   into f:"
  78       return "F_RESULT"
  79       assert (false, "I'll never go there")
  80    catch _ ->
  81       assert (false, "No exception should be thrown")
  82    finally
  83       print "   I do the finally before leaving f()"
  84    end
  85 end
  86 local fr = f()
  87 printf("   f returned %q", fr)
  88
  89
  90 ----------------------------------------------------------------------
  91 print "*) done."