doAssertRaises improvements; nimscript supports except Exception as e (#15765)

* doAssertRaises now correctly handles foreign exceptions; now shows which exception is raised on mismatch
* nimscript now handles `Exception as e`
* remove catch-all doAssertRaises overload from this PR

Co-authored-by: Andreas Rumpf <[email protected]>

Author: timotheecour

changelog.md

@@ -31,10 +31,11 @@
 - Removed deprecated `iup` module from stdlib, it has already moved to
   [nimble](https://github.com/nim-lang/iup).
 
-
+- `doAssertRaises` now correctly handles foreign exceptions.
 
 ## Language changes
 
+- `nimscript` now handles `except Exception as e`
 - The `cstring` doesn't support `[]=` operator in JS backend.
 
 

lib/system.nim

@@ -2360,7 +2360,8 @@ when notJSnotNims and hostOS != "standalone":
     ##
     ## **Warning**: Only use this if you know what you are doing.
     currException = exc
-
+elif defined(nimscript):
+  proc getCurrentException*(): ref Exception {.compilerRtl.} = discard
 
 when notJSnotNims:
   {.push stackTrace: off, profiler: off.}

lib/system/assertions.nim

@@ -81,30 +81,31 @@ template onFailedAssert*(msg, code: untyped): untyped {.dirty.} =
     code
 
 template doAssertRaises*(exception: typedesc, code: untyped) =
-  ## Raises ``AssertionDefect`` if specified ``code`` does not raise the
-  ## specified exception. Example:
+  ## Raises ``AssertionDefect`` if specified ``code`` does not raise `exception`.
+  ## Example:
   ##
   ## .. code-block:: nim
   ##  doAssertRaises(ValueError):
   ##    raise newException(ValueError, "Hello World")
   var wrong = false
+  const begin = "expected raising '" & astToStr(exception) & "', instead"
+  const msgEnd = " by: " & astToStr(code)
+  template raisedForeign = raiseAssert(begin & " raised foreign exception" & msgEnd)
   when Exception is exception:
     try:
       if true:
         code
       wrong = true
-    except Exception:
-      discard
+    except Exception as e: discard
+    except: raisedForeign()
   else:
     try:
       if true:
         code
       wrong = true
     except exception:
       discard
-    except Exception:
-      raiseAssert(astToStr(exception) &
-                  " wasn't raised, another error was raised instead by:\n"&
-                  astToStr(code))
+    except Exception as e: raiseAssert(begin & " raised '" & $e.name & "'" & msgEnd)
+    except: raisedForeign()
   if wrong:
-    raiseAssert(astToStr(exception) & " wasn't raised by:\n" & astToStr(code))
+    raiseAssert(begin & " nothing was raised" & msgEnd)

tests/test_nimscript.nims

@@ -81,3 +81,9 @@ block: # #14142
   discard dirExists("/usr")
   discard fileExists("/usr/foo")
   discard findExe("nim")
+
+block:
+  doAssertRaises(AssertionDefect): doAssert false
+  try: doAssert false
+  except Exception as e:
+    discard