mojom/mojom_parser/generated/README.md

Generated  Files
==================

The intermediate representation passed from the Mojom parser (the frontend
of the Mojom compiler) to the code generators (the backend of the Mojom
Compiler) is a `MojomFileGraph` described in  mojom_types.mojom and
mojom_files.mojom in mojo/public/interfaces/bindings. Thus the Mojom compiler
uses Mojo serialization to serialize the intermediate representation.

This situation potentially entails a circular dependency because it means that
in  order to build the Mojom compiler it is necessary to use code that has been
generated by the Mojom compiler. In order to break this circular dependency we
check in the generated code needed by the compiler rather than generating it
while building the compiler.

This directory contains the checked-in generated Go code used by the frontend
of the compiler:
mojom_files/mojom_files.mojom.go and
mojom_types/mojom_types.mojom.go.

The backend of the Mojom compiler is  written in Python and the corresponding
generated Python files may be found in
mojo/public/tools/bindings/pylib/mojom/generate/generated/mojom_files_mojom.py
and
mojo/public/tools/bindings/pylib/mojom/generate/generated/mojom_types_mojom.py

### Instructions for updating these files
1) Make changes to mojom_types.mojom and mojom_files.mojom. This may be done
either in the same patch as everything below or in its own initial patch.
2) Compile these files to produce new generated files:
ninja -C out/Debug mojo/public/interfaces/bindings.
3) Copy the newly generated mojom_files.mojom.go and mojom_types.mojom.go
into the appropriate locations in this directory.
4) mojom_files.mojom.go needs to be manually patched in a minor way. In the
import section at the top replace "mojo/public/interfaces/bindings/mojom_types"
with "mojom/mojom_parser/generated/mojom_types".
5) Update the Go code in the serialization module of the parser to compensate
for the changes if necessary. (Not necessary if the changes in step 1 were
backward compatible.)
6) Perform the analog of steps 3, 4, 5 for the Python code in the backend of
the compiler. See
mojo/public/tools/bindings/pylib/mojom/generate/generated/README.md
for instructions.
7) Land a patch containing your changes from steps 3 through 6.