e039ad26c5 [editor-core] extract logic for determining root doc from snapshot (#37043)
* [editor-core] hold the one threshold that decides which store owns the file tree

HISTORY_FILE_TREE_STAGE is five literals across the services that consume this
library -- web backend, web editor, real-time, third-party-datastore,
github-sync -- linked by comments saying which other copies they are aligned
with. What the docstring here says is what goes wrong: this is the single thing
that decides which storage is authoritative, a project crosses it once with no
way back, and a copy that drifts sends a whole service's writes to the store
nothing reads any more. Silently, and for good.

overleaf-editor-core is where it goes: every one of the five already depends on
it, the editor included, and the library that defines what a file tree is can say
where one lives. The consumers adopt it separately; this is the definition they
adopt.

historyIsSourceOfTruth goes with it, and refuses a stage that is neither absent
nor a number rather than reading it as low -- web's copy coerced, which turned a
corrupt stage into a permanent mongo write. Absent stays "below the gate": a
project that never migrated has no stage.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

* [editor-core] hold which doc a project opens on

History records it as `main: true` on the file, and nothing derives it: every
writer that creates a project has to record it, or the project compiles nothing
until the user picks a file. So the rule for choosing one, and the operations
that record it, go where a file tree is defined rather than with any one writer.

The rule is the one web has always applied, over a snapshot instead of a mongo
tree: of the docs that declare a document class, the one nearest the project
root, alphabetically among equals, so that the same files always give the same
answer. A project that already records a root doc keeps it -- that is a user's
choice and not something to re-derive.

Whether a doc could be the one is asked of content rather than of a store to read
it from: a writer creating a project has each doc's content in its hands as it
stores it, so reading them back would be a second read of every one. The choice
is then made from the pathnames alone.

The extension list joins the others in text_file_defaults for the reason they are
there: a writer holding a shorter copy leaves a project with nothing to compile.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

* [editor-core] say why a store built for a consumer does not need getBlob

ReadWriteBlobStore is BlobStore without the lookup by hash, and the type said so
without saying why a consumer can do without it. getBlob is reached only for a
file stored as a bare hash, and one of those does not leave history-v1:
chunk_store's lazyLoadHistoryFiles attaches blob metadata to every snapshot and
change it serves, so a file arrives already knowing its own lengths.

That is what the contract rests on, and a store that reimplemented the
classification rule to answer the lookup anyway would be a second opinion on
whether a file is editable. The reasoning was what was missing, rather than the
type.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

* [editor-core] say what makes a doc a root doc candidate

The sentence naming the two halves of the check had lost the first one, and read
"named as a root doc may be named". It is the extension that is tested: one of
DEFAULT_ROOT_DOC_EXTENSIONS, and a document class declared in the content.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

* [editor-core] hold the doc flags a file's metadata can carry in one place

`main` is not the only flag a doc carries -- `mainBibliography` marks the file
references are added to -- and both live in the same metadata, which
SetFileMetadataOperation replaces wholesale rather than merges. So every writer
that sets one has to write the others out again, and every reader that asks
whether a file is a doc has to know the whole list.

root_doc was spelling all three of those for itself against `main` alone: it
tested the key by hand, refused a file whose metadata held anything else, and
cleared the metadata to `{}` when moving the root doc elsewhere. Against a file
that is also the main bibliography, the first two refuse a legitimate root doc
and the third silently drops the bibliography.

The helpers answer it once: which keys are doc flags, whether metadata holds only
those, and what metadata with one flag changed looks like. root_doc uses them
throughout, and the schema takes both flags on one file.

Co-Authored-By: Mathias Jakobsen <mathias.jakobsen@overleaf.com>
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

* [editor-core] ask the snapshot which doc carries a flag

Finding the file a doc flag is set on is the same search whichever flag is being
asked about, and it belongs to the snapshot rather than to the caller: it walks
the snapshot's own pathnames, and it is the snapshot that knows a file's
metadata without its content being loaded.

root_doc's mainPathname is that search for `main`, and now delegates. It gains
the check it was missing: a file whose metadata holds anything besides doc flags
came from outside the editor, so a stale `main` on it does not make it the root
doc -- which is already what setMainPathnameOperations refuses to write.

Co-Authored-By: Mathias Jakobsen <mathias.jakobsen@overleaf.com>
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

* [editor-core] drop mainPathname for the snapshot method behind it

It became a second name for `snapshot.getPathnameWithDocFlag('main')` and nothing
in the library was left calling it but chooseRootDoc, which asks the snapshot
directly now. Its two tests go with it: Snapshot's own cover the same two answers,
and more of them.

Callers outside the library ask the snapshot too.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>
Co-authored-by: Mathias Jakobsen <mathias.jakobsen@overleaf.com>
GitOrigin-RevId: b3f503aa3e94ea8b6524d83f910fe33dc381c0a5
2026-09-17 12:08:31 +00:00
2026-03-09 09:06:41 +00:00


Overleaf

An open-source online real-time collaborative LaTeX editor.

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Figure 1: A screenshot of a project being edited in Overleaf Community Edition.

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