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Introduce explicit VFS in Python MjVfs

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This change introduces MjVFS, an explicit object to mirror the C mjVFS. This is meant to replace the MjSpec.assets dict. This latter while convenient guides users towards harmful authoring patterns with respect to data duplication and spec attachment workflows. Making VFS management explicit should encourage better memory usage and allow us to make better compile time optimizations.

From this change, `spec.assets` is deprecated. However we will temporarily support backwards compatibility due to the wide spread usage. An error will be thrown if calling code tries to use a spec that uses both the assets dict and the new MjVfs.

PiperOrigin-RevId: 908772050
Change-Id: I77c6d0369307fc300c954768fed17401261e18da
This commit is contained in:
Sam Haves
2026-05-01 09:33:43 -07:00
committed by Copybara-Service
parent 910b3336ed
commit 723b8b1ea6
10 changed files with 599 additions and 78 deletions
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python/mujoco/specs_wrapper.cc
+31 -29
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@@ -15,6 +15,7 @@
#include "specs_wrapper.h"
#include <cstddef> // IWYU pragma: keep
#include <optional>
#include <string>
#include <string_view> // IWYU pragma: keep
#include <vector> // IWYU pragma: keep
@@ -87,44 +88,45 @@ MjSpec& MjSpec::operator=(MjSpec&& other) {
MjSpec::~MjSpec() { mj_deleteSpec(ptr); }
raw::MjModel* MjSpec::Compile() {
if (assets.empty()) {
raw::MjModel* m;
{
// Release GIL before calling mj_compile which may spawn threads
py::gil_scoped_release no_gil;
m = mj_compile(ptr, 0);
}
if (!m || mjs_isWarning(ptr)) {
throw py::value_error(mjs_getError(ptr));
}
return m;
raw::MjModel* MjSpec::Compile(mjVFS* vfs) {
if (vfs != nullptr && !assets.empty()) {
throw py::value_error("Cannot specify both 'vfs' and 'assets'.");
}
mjVFS vfs;
mj_defaultVFS(&vfs);
for (const auto& asset : assets) {
std::string buffer_name = py::cast<std::string>(asset.first).c_str();
std::string buffer = py::cast<std::string>(asset.second);
const int vfs_error = InterceptMjErrors(mj_addBufferVFS)(
&vfs, buffer_name.c_str(), buffer.c_str(), buffer.size());
if (vfs_error) {
mj_deleteVFS(&vfs);
if (vfs_error == 2) {
throw py::value_error("Repeated file name in assets dict: " +
buffer_name);
} else {
throw py::value_error("Asset failed to load: " + buffer_name);
std::optional<mjVFS> local_vfs;
if (vfs == nullptr) {
vfs = &local_vfs.emplace();
mj_defaultVFS(vfs);
for (const auto& asset : assets) {
std::string buffer_name = py::cast<std::string>(asset.first).c_str();
std::string buffer = py::cast<std::string>(asset.second);
const int vfs_error = InterceptMjErrors(mj_addBufferVFS)(
vfs, buffer_name.c_str(), buffer.c_str(), buffer.size());
if (vfs_error) {
mj_deleteVFS(vfs);
if (vfs_error == 2) {
throw py::value_error("Repeated file name in assets dict: " +
buffer_name);
} else {
throw py::value_error("Asset failed to load: " + buffer_name);
}
}
}
}
raw::MjModel* m;
{
// Release GIL before calling mj_compile which may spawn threads
py::gil_scoped_release no_gil;
m = mj_compile(ptr, &vfs);
m = mj_compile(ptr, vfs);
}
mj_deleteVFS(&vfs);
if (local_vfs.has_value()) {
// vfs points at local_vfs value.
mj_deleteVFS(vfs);
local_vfs = std::nullopt;
}
if (!m || mjs_isWarning(ptr)) {
throw py::value_error(mjs_getError(ptr));
}