tests: enable the exceptions category for all targets (nim-works#1082)

## Summary

Clean up the category and enable it for all targets by default. This
significantly increases test coverage of exceptions for the JS and VM
targets.

## Details

**General changes/cleanup:**
* references to issues like `nim-works#1234` are replaced with proper GitHub
  links
* the `targets` key is removed for tests that should be run on all
  targets
* usage of `cmd` is replaced with usage of `matrix` (allowing for
  multi-target testing)
* `write(stdout, ...)` is replaced with `echo` in order to support the
  JS and VM targets
* execution of `static:` blocks is replaced with using the VM target,
  when the test is not specific to compile-time execution
* tests that don't work but should are marked as `knownIssue`

**Specific changes:**
* where not necessary for the test, `getCurrentExceptionMsg` is
  replaced with `getCurrentException().msg`, as the former is not yet
  supported by the VM
* `texceptions2.nim` is removed -- it's redundant with `texception.nim`
* `texception_message_null_byte.nim` is turned into a normal test that
  doesn't rely on self-execution

testament/testament.nim

@@ -1110,7 +1110,7 @@ func nativeTarget(): TTarget {.inline.} =
 func defaultTargets(category: Category): set[TTarget] =
   const standardTargets = {nativeTarget()}
   case category.string
-  of "lang", "lang_callable":
+  of "lang", "lang_callable", "exception":
     {targetC, targetJs, targetVM}
   of "arc", "avr", "destructor", "distros", "dll", "gc", "osproc", "parallel",
      "realtimeGC", "threads", "views", "valgrind":

tests/exception/tassignment.nim

@@ -1,5 +1,4 @@
 discard """
-  targets: "c js vm"
   description: '''
     Tests for assignments where an exception is raised during evaluation of
     the right-hand side

tests/exception/tasync_stacktrace_gc.nim

@@ -1,5 +1,4 @@
 discard """
-  matrix: "--gc:arc"
   description: '''
   . From https://github.com/nim-lang/Nim/issues/18620
     Stacktrace when using async with arc/orc is different than
@@ -9,6 +8,7 @@ discard """
     the stacktrace with arc/orc gives little help in finding out
     where the problem is.
   '''
+  knownIssue.js vm: "`getStackTraceEntries` is not yet supported"
 """
 
 proc hello() =

tests/exception/tcontinuexc.nim

@@ -1,5 +1,7 @@
 discard """
-  outputsub: "ECcaught"
+  outputsub: '''E
+C
+caught'''
   exitcode: "1"
 """
 type
@@ -17,8 +19,8 @@ try:
     try:
       genErrors("error!")
     except ESomething:
-      stdout.write("E")
-    stdout.write("C")
+      echo "E"
+    echo "C"
     raise newException(EsomeotherErr, "bla")
 finally:
   echo "caught"

tests/exception/tdefer1.nim

@@ -7,7 +7,7 @@ B
 A'''
 """
 
-# bug #1742
+# bug https://github.com/nim-lang/nim/issues/1742
 
 import strutils
 let x = try: parseInt("133a")

tests/exception/tdont_overwrite_typename.nim

@@ -1,10 +1,9 @@
 discard """
-  targets: "c"
   output: '''Check passed
 Check passed'''
 """
 
-# bug #5628
+# bug https://github.com/nim-lang/nim/issues/5628
 
 proc checkException(ex: ref Exception) =
   doAssert(ex.name == cstring"ValueError")

tests/exception/texcas.nim

@@ -1,5 +1,4 @@
 discard """
-  targets: "c"
   output: '''
 Hello
 Hello
@@ -34,7 +33,7 @@ test[Exception]()
 test2()
 testTryAsExpr(5)
 
-# see bug #7115
+# bug https://github.com/nim-lang/nim/issues/7115
 doAssert(not compiles(
   try: 
     echo 1

tests/exception/texception_inference.nim

@@ -1,7 +1,6 @@
 discard """
   output: '''good'''
-  joinable: false
-  cmd: "nim c --gc:orc -d:release $file"
+  matrix: "-d:release"
 """
 
 type

tests/exception/texception_message_null_byte.nim

@@ -5,46 +5,14 @@ description: '''
   . Error output produced by raise newException is inconsistent with other
     IO such as echo or stdout.write.
 '''
-joinable: false
+matrix: ";-d:debug;-d:danger"
+outputsub: "` and works fine! [Exception]"
+exitcode: 1
 """
 
-# marked as not joinable because this test self-executes
-
+# `\0` not preserved on windows, so only the trailing part can be reliably
+# tested for
 const msg = "This char is `" & '\0' & "` and works fine!"
 
-when defined nim_t13115:
-  # bug #13115
-  template fn =
-    raise newException(Exception, msg)
-  when defined nim_t13115_static:
-    static: fn()
-  fn()
-else:
-  import std/[osproc,strformat,os,strutils]
-  proc main =
-    const nim = getCurrentCompilerExe()
-    const file = currentSourcePath
-    for b in "c js".split:
-      when defined(openbsd):
-        if b == "js":
-          # xxx bug: pending #13115
-          # remove special case once nodejs updated >= 12.16.2
-          # refs https://github.com/nim-lang/Nim/pull/16167#issuecomment-738270751
-          continue
-
-      # save CI time by avoiding mostly redundant combinations as far as this bug is concerned
-      var opts = case b
-        of "c": @["", "-d:nim_t13115_static", "-d:danger", "-d:debug"]
-        of "js": @["", "-d:nim_t13115_static"]
-        else: @[""]
-
-      for opt in opts:
-        let cmd = fmt"{nim} r -b:{b} -d:nim_t13115 {opt} --hints:off {file}"
-        let (outp, exitCode) = execCmdEx(cmd)
-        when defined windows:
-          # `\0` not preserved on windows
-          doAssert "` and works fine!" in outp, cmd & "\n" & msg
-        else:
-          doAssert msg in outp, cmd & "\n" & msg
-        doAssert exitCode == 1
-  main()
+# bug https://github.com/nim-lang/nim/issues/13115
+raise newException(Exception, msg)

tests/exception/texception_name.nim

@@ -1,6 +1,5 @@
 discard """
   description: "Tests to make sure that the Exception.name field is set"
-  targets: "c js"
 """
 
 template test(desc, body) {.dirty.} =
@@ -9,8 +8,6 @@ template test(desc, body) {.dirty.} =
     proc wrapper() =
       body
 
-    # TODO: once it's available in testament, use the VM target instead
-    static: wrapper()
     wrapper()
 
 
@@ -46,10 +43,12 @@ test "Name is set on raise if it was unset":
   except IOError as e:
     doAssert e.name == "IOError"
 
-
-# fails for the VM. See ``texception_name_vm_issue.nim``
-block no_override_empty:
+test "Don't override an explicitly empty name":
   try:
     raise (ref IOError)(name: "") # explicitly set name to an empty string
   except IOError as e:
-    doAssert e.name == ""
+    when defined(vm):
+      # see ``texception_name_vm_issue.nim``
+      doAssert e.name != "", "works now"
+    else:
+      doAssert e.name == ""

tests/exception/texception_name_vm_issue.nim

@@ -1,14 +1,13 @@
 discard """
-  action: compile
+  target: "vm"
   description: '''An empty exception name is overridden on raise when run in
                   the VM'''
   knownIssue
 """
 
 # The VM treats `cstring(nil)` and `cstring("")` as the same thing
 
-static:
-  try:
-    raise (ref CatchableError)(name: "")
-  except CatchableError as e:
-    doAssert e.name == ""
+try:
+  raise (ref CatchableError)(name: "")
+except CatchableError as e:
+  doAssert e.name == ""

tests/exception/texceptions.nim

@@ -1,5 +1,4 @@
 discard """
-  matrix: "--exceptions:goto"
   output: '''
 
 BEFORE
@@ -14,6 +13,9 @@ BEFORE
 EXCEPT: IOError: hi
 FINALLY
 '''
+  knownIssue.vm: '''
+    Exception/finally handling is largely disfunctional in the VM
+  '''
 """
 
 echo ""
@@ -57,7 +59,8 @@ proc return_in_except =
     raise newException(IOError, "hi")
 
   except:
-    echo "EXCEPT: ", getCurrentException().name, ": ", getCurrentExceptionMsg()
+    let e = getCurrentException()
+    echo "EXCEPT: ", e.name, ": ", e.msg
     return
 
   finally:
@@ -66,7 +69,7 @@ proc return_in_except =
 try: return_in_except()
 except: echo "RECOVER"
 
-block: #10417
+block: # https://github.com/nim-lang/nim/issues/10417
   proc moo() {.noreturn.} = discard
 
   let bar =
@@ -84,10 +87,10 @@ block:
       try:
         raise newException(ValueError, "xx")
       except:
-        doAssert("xx" == getCurrentExceptionMsg())
+        doAssert("xx" == getCurrentException().msg)
         raise newException(KeyError, "yy")
     except:
-      doAssert("yy" == getCurrentExceptionMsg())
+      doAssert("yy" == getCurrentException().msg)
       result.add(1212)
     try:
       try:

tests/exception/texcpt1.nim

@@ -29,7 +29,7 @@ proc blah(): int =
 
 echo blah()
 
-# Issue #7845, raise generic exception
+# https://github.com/nim-lang/nim/issues/7845, raise generic exception
 var x: ref ESomethingGen[int]
 new(x)
 try: