Make fastprogress an optional dependency (#853)

* Make fastprogress an optional dependency

fastprogress 1.1.0+ introduced an unconditional top-level IPython import
and a heavy python-fasthtml transitive dependency (starlette, uvicorn,
etc.), breaking imports in environments without IPython installed.

Fixes #812, addresses PR #852:
- Remove fastprogress and ipython from hard dependencies
- Add fastprogress>=1.0.0,<1.1 as optional extra: pip install "blackjax[progress]"
- Lazy-import fastprogress inside _update_bar() so it is only required
  when progress_bar=True is actually used

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* ci: install blackjax[progress] in test env

Tests that use progress_bar=True need fastprogress, which is now an
optional dependency. Install it via the [progress] extra.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: junpenglao

.github/workflows/test.yml

@@ -34,7 +34,7 @@ jobs:
     - name: Set up test environment
       run: |
         python -m pip install --upgrade pip
-        pip install .
+        pip install ".[progress]"
         less requirements.txt | grep 'pytest\|chex' | xargs -i -t pip install {}
     - name: Run tests
       run: |

blackjax/progress_bar.py

@@ -16,7 +16,6 @@
 """
 from threading import Lock
 
-from fastprogress.fastprogress import progress_bar
 from jax import lax
 from jax.experimental import io_callback
 from jax.numpy import array
@@ -42,6 +41,13 @@ def _calc_chain_idx(iter_num):
         return idx
 
     def _update_bar(arg, chain_id):
+        try:
+            from fastprogress.fastprogress import progress_bar
+        except ImportError as e:
+            raise ImportError(
+                "fastprogress is required to use progress bars. "
+                "Install it with: pip install fastprogress"
+            ) from e
         chain_id = int(chain_id)
         if arg == 0:
             chain_id = _calc_chain_idx(arg)

pyproject.toml

@@ -31,8 +31,6 @@ classifiers = [
     "Topic :: Scientific/Engineering :: Mathematics",
 ]
 dependencies = [
-    "fastprogress>=1.0.0",
-    "ipython",
     "jax>=0.9.0",
     "jaxlib>=0.9.0",
     "numpy>=1.25",
@@ -42,6 +40,9 @@ dependencies = [
 ]
 dynamic = ["version"]
 
+[project.optional-dependencies]
+progress = ["fastprogress>=1.0.0,<1.1"]
+
 [project.urls]
 homepage = "https://github.com/blackjax-devs/blackjax"
 documentation = "https://blackjax-devs.github.io/blackjax/"