fix open file leak when running --debugger:native (#13832)

compiler/cgen.nim

@@ -1924,8 +1924,8 @@ proc shouldRecompile(m: BModule; code: Rope, cfile: Cfile): bool =
 # it would generate multiple 'main' procs, for instance.
 
 proc writeModule(m: BModule, pending: bool) =
+  template onExit() = close(m.ndi, m.config)
   let cfile = getCFile(m)
-
   if true or optForceFullMake in m.config.globalOptions:
     if moduleHasChanged(m.g.graph, m.module):
       genInitCode(m)
@@ -1943,6 +1943,7 @@ proc writeModule(m: BModule, pending: bool) =
       when hasTinyCBackend:
         if conf.cmd == cmdRun:
           tccgen.compileCCode($code)
+          onExit()
           return
 
       if not shouldRecompile(m, code, cf): cf.flags = {CfileFlag.Cached}
@@ -1966,7 +1967,7 @@ proc writeModule(m: BModule, pending: bool) =
                    obj: completeCfilePath(m.config, toObjFile(m.config, cfile)), flags: {})
     if not fileExists(cf.obj): cf.flags = {CfileFlag.Cached}
     addFileToCompile(m.config, cf)
-  close(m.ndi)
+  onExit()
 
 proc updateCachedModule(m: BModule) =
   let cfile = getCFile(m)

compiler/ndi.nim

@@ -17,6 +17,8 @@ type
     enabled: bool
     f: File
     buf: string
+    filename: AbsoluteFile
+    syms: seq[PSym]
 
 proc doWrite(f: var NdiFile; s: PSym; conf: ConfigRef) =
   f.buf.setLen 0
@@ -28,13 +30,20 @@ proc doWrite(f: var NdiFile; s: PSym; conf: ConfigRef) =
   f.f.writeLine("\t", toFullPath(conf, s.info), "\t", f.buf)
 
 template writeMangledName*(f: NdiFile; s: PSym; conf: ConfigRef) =
-  if f.enabled: doWrite(f, s, conf)
+  if f.enabled: f.syms.add s
 
 proc open*(f: var NdiFile; filename: AbsoluteFile; conf: ConfigRef) =
   f.enabled = not filename.isEmpty
   if f.enabled:
-    f.f = open(filename.string, fmWrite, 8000)
+    f.filename = filename
     f.buf = newStringOfCap(20)
 
-proc close*(f: var NdiFile) =
-  if f.enabled: close(f.f)
+proc close*(f: var NdiFile, conf: ConfigRef) =
+  if f.enabled:
+    f.f = open(f.filename.string, fmWrite, 8000)
+    doAssert f.f != nil, f.filename.string
+    for s in f.syms:
+      doWrite(f, s, conf)
+    close(f.f)
+    f.syms.reset
+    f.filename.reset