MarkdownToNotebook: Symbol-page Tech Notes build a malformed, double-nested TechNotesSection group (template ships a group + Tutorials placeholder, not a bare header cell)

[mbahram]

Summary

Symbol-page Tech Notes are filled by replacing the header cell (MarkdownToNotebook.wl, symbolNotebook, line 3966):

If[ rt =!= {} && paclet =!= "",
    nb = nb /. tns : Cell[_, "TechNotesSection", ___] :> techNotesGroup[tns, rt, paclet]
]

with techNotesGroup (line 2760) wrapping the matched cell into a fresh group:

techNotesGroup[header_Cell, entries_List, paclet_String] := Cell[CellGroupData[
    Prepend[tutorialLinkCell[#, paclet] & /@ entries, header], Open]]

Its comment (line ~2734) states the premise: the Symbol template "ships the TechNotesSection header as a bare cell rather than a group with a placeholder inside."

That premise is false on this installation. FunctionBaseTemplateExt.nb (loaded via docTemplate, from $InstallationDirectory/AddOns/Applications/DocumentationTools/FrontEnd/TextResources/) ships the header INSIDE an existing group:

CellGroupData[{ Cell[_, "TechNotesSection"], Cell[_, "Tutorials"] }, ...]

HEAD's own comment agrees (line 3846): "the XXXX placeholder the template ships inside the TechNotesSection group."

Effect

Because /. matches the inner Cell[_, "TechNotesSection", ___] (the header inside the existing group), techNotesGroup wraps that header into a new group, producing a group nested directly inside the original group. The result is a CellGroupData whose head cell is itself a Cell[CellGroupData[...]], i.e. an outer section with no heading cell at its own level.

Measured on a built Symbol page with RelatedTutorials set:

	working tree	HEAD (486a861)
TechNotesSection-bearing groups	2	1
malformed CellGroupData[{Cell[CellGroupData[..]], ...}]	1	0
group shape	{{GROUP, {TechNotesSection, Tutorials}}} nested	{TechNotesSection, Tutorials} flat

HEAD produces the correct flat group; the working tree produces a double-nested, malformed one.

Repro

sym.md:

---
Title: FooBar
Template: Symbol
Name: FooBar
Paclet: My`Pac`
Context: My`Pac`
RelatedTutorials:
  - Getting Started
  - [Advanced Topics](AdvancedGuide)
---

## Usage

`FooBar[x]` returns a thing.

Get[".../MarkdownToNotebook.wl"];
nb = MarkdownToNotebook["sym.md", "Evaluate" -> False];
Length @ Cases[nb, CellGroupData[{Cell[CellGroupData[__], ___], ___}, ___], Infinity]   (* 1, should be 0 *)

Which change introduced it

The uncommitted merge kept the local techNotesGroup / tutorialLinkCell implementation in place of upstream's techNoteContent + fillDocCells[nb, "Tutorials", ...]. fillDocCells fills the Tutorials placeholder inside the existing group and yields the correct flat structure; the wrap approach does not, given the actual template shape.

Fix options

• Revert to the fillDocCells[nb, "Tutorials", ...] approach (fills the placeholder in the group the template already ships), or
• Match and replace the whole group Cell[CellGroupData[{Cell[_, "TechNotesSection", ___], ___}, ___], ___] and rebuild it flat, rather than matching only the inner header cell.

Note

Correctness depends on the installed DocumentationTools template. On the current install the template ships a group, so the wrap approach is wrong. If a future template ships a bare TechNotesSection cell, the premise (and the wrap approach) would hold; the code should not silently assume one shape.

Severity

Medium-high: every Symbol page with RelatedTutorials builds a malformed TechNotesSection group.

[sw1sh]

Not reproducible on current `main` (4404dc5). Filed against an uncommitted working tree that was never committed.

`techNotesGroup` does not exist in the source — `grep` for it returns nothing. The only `TechNotesSection` mention is the comment the report itself quotes as HEAD's correct premise: "the XXXX placeholder the template ships inside the TechNotesSection group". So no group is re-wrapped and there is no double nesting.