A simple declaration exporter for Lean 4 using the Lean 4 NDJSON export format

How to Run

1. Build lean4export with lake build

2. Call the lean4export binary with the correct lake env set up.

lake env <path to lean4export binary> <lean file without .lean suffix>+

For example, let's assume we're working in the mathlib4 directory, with the following structure:

|__ mathlib4 (*we are here)
|__ lean4export

We can invoke the exporter on the "top level" mathlib file and export mathlib with the following command:

lake env ../lean4export/.lake/build/bin/lean4export Mathlib > out.ndjson

This exports the contents of the given Lean module (here just the top level Mathlib module in the Mathlib.lean file), and its transitive dependencies. A specific list of declarations to be exported from these modules can be given after a separating --, and more than one module can be passed to the initial invocation by including more than one name (separated with a space).

Options

The option --export-unsafe can be used to include unsafe and partial declarations in the export file, which are omitted by default. This may be useful for testing and debugging other tools, where unsafe or partial declarations can serve as negative examples.

The option --export-mdata can be used to include Expr.mdata items in the export file, which are removed by default as they should not have an effect on type checking.

The option --ignore-missing can be used to skip constants that are not found in the imported environment, rather than panicking.