add simple writeStackTrace for JS backend (nim-lang#16016)

* add simple writeStackTrace for JS backend

* add testcase for writeStackTrace

* changelog

changelog.md

@@ -47,6 +47,8 @@
 - `repr` now doesn't insert trailing newline; previous behavior was very inconsistent,
   see #16034. Use `-d:nimLegacyReprWithNewline` for previous behavior.
 
+- `writeStackTrace` is available in JS backend now.
+
 ## Language changes
 
 - `nimscript` now handles `except Exception as e`

lib/system.nim

@@ -1765,7 +1765,7 @@ when notJSnotNims and defined(nimSeqsV2):
 
 {.pop.}
 
-when notJSnotNims:
+when not defined(nimscript):
   proc writeStackTrace*() {.tags: [], gcsafe, raises: [].}
     ## Writes the current stack trace to ``stderr``. This is only works
     ## for debug builds. Since it's usually used for debugging, this

lib/system/jssys.nim

@@ -105,6 +105,11 @@ proc rawWriteStackTrace(): string =
   else:
     result = "No stack traceback available\n"
 
+proc writeStackTrace() =
+  var trace = rawWriteStackTrace()
+  trace.setLen(trace.len - 1)
+  echo trace
+
 proc getStackTrace*(): string = rawWriteStackTrace()
 proc getStackTrace*(e: ref Exception): string = e.trace
 

tests/js/twritestacktrace.nim

@@ -0,0 +1,12 @@
+discard """
+  cmd: "nim js --panics:on $file"
+  output: '''Traceback (most recent call last)
+twritestacktrace.nim(12) at module twritestacktrace
+twritestacktrace.nim(10) at twritestacktrace.hello
+'''
+"""
+
+proc hello() =
+  writeStackTrace()
+
+hello()