fixes #19396; Nimdoc hide nonexported fields (#21305)

* suppresses non-exported fields of types and adds command-line option to re-enable this if desired

* corrected the doctest that produced a CI error

* an embarrassingly bad error in reasoning

* modified a nimdoc test to reflect updated behavior

* needed another change to bring utils.html doctest in sync with update

* add info

* fix nimdoc

* lint

* render postfix

* fixes a problem

* fixes nimdoc

* fix nimdoc

---------

Co-authored-by: johnperry-math <john.perry@usm.edu>
Co-authored-by: johnperry-math <devotus@yahoo.com>

compiler/renderer.nim

@@ -23,7 +23,8 @@ type
   TRenderFlag* = enum
     renderNone, renderNoBody, renderNoComments, renderDocComments,
     renderNoPragmas, renderIds, renderNoProcDefs, renderSyms, renderRunnableExamples,
-    renderIr, renderExpandUsing
+    renderIr, renderNonExportedFields, renderExpandUsing
+
   TRenderFlags* = set[TRenderFlag]
   TRenderTok* = object
     kind*: TokType
@@ -652,7 +653,7 @@ proc gcommaAux(g: var TSrcGen, n: PNode, ind: int, start: int = 0,
     inHideable = false
 
 proc gcomma(g: var TSrcGen, n: PNode, c: TContext, start: int = 0,
-            theEnd: int = - 1) =
+            theEnd: int = -1) =
   var ind: int
   if rfInConstExpr in c.flags:
     ind = g.indent + IndentWidth
@@ -1481,9 +1482,11 @@ proc gsub(g: var TSrcGen, n: PNode, c: TContext, fromStmtList = false) =
   of nkRecList:
     indentNL(g)
     for i in 0..<n.len:
-      optNL(g)
-      gsub(g, n[i], c)
-      gcoms(g)
+      if n[i].kind == nkIdentDefs and n[i][0].kind == nkPostfix or
+                        renderNonExportedFields in g.flags:
+        optNL(g)
+        gsub(g, n[i], c)
+        gcoms(g)
     dedent(g)
     putNL(g)
   of nkOfInherit: