Add support for env variable TACH_CACHE_DIR

docs/usage/caching.md

@@ -32,7 +32,7 @@ When all of these match a previous cache entry, the cached results are printed d
 
 ## Cache storage
 
-The computation cache exists within the `.tach` directory in your project root. The directory is managed by Tach, and your cached results are stored on-disk on each machine where tasks are run.
+The computation cache exists within the directory defined by the `TACH_CACHE_DIR` environment variable (default is `.tach` in your project root). The directory is managed by Tach, and your cached results are stored on-disk on each machine where tasks are run.
 
 We are currently working on a _remote cache_ backend, which will allow multiple developers and CI environments to share a centralized cache to maximize the hit rate. If you are interested in this functionality, reach out through a [GitHub issue](https://github.com/gauge-sh/tach/issues) or via email: [evan@gauge.sh](mailto://evan@gauge.sh); [caelean@gauge.sh](mailto://caelean@gauge.sh)!
 

python/tach/cache/access.py

@@ -3,23 +3,23 @@
 import uuid
 from typing import TYPE_CHECKING
 
-from tach.cache.setup import resolve_dot_tach
+from tach.cache.setup import get_cache_path, resolve_cache_path
 
 if TYPE_CHECKING:
     from pathlib import Path
 
 
 def get_uid(project_root: Path) -> uuid.UUID | None:
-    info_path = project_root / ".tach" / "tach.info"
+    info_path = get_cache_path(project_root) / "tach.info"
     if not info_path.exists():
-        resolve_dot_tach(project_root)
+        resolve_cache_path(project_root)
     contents = info_path.read_text().strip()
     uid = uuid.UUID(contents)
     return uid
 
 
 def get_latest_version(project_root: Path) -> str | None:
-    latest_version_path = project_root / ".tach" / ".latest-version"
+    latest_version_path = get_cache_path(project_root) / ".latest-version"
     if not latest_version_path.exists():
         return
     version = latest_version_path.read_text().strip()

python/tach/cache/setup.py

@@ -1,24 +1,38 @@
 from __future__ import annotations
 
+import pathlib
 import uuid
+from os import getenv
 from pathlib import Path
 
 from tach import __version__
 
 
-def resolve_dot_tach(project_root: Path) -> Path | None:
+def get_cache_path(project_root: Path) -> Path:
+    env_value = getenv("TACH_CACHE_DIR")
+
+    if env_value is None:
+        return project_root / ".tach"
+
+    if not pathlib.Path.is_absolute(pathlib.PurePath(env_value)):
+        return project_root / env_value
+
+    return Path(env_value)
+
+
+def resolve_cache_path(project_root: Path) -> Path | None:
     def _create(path: Path, is_file: bool = False, file_content: str = "") -> None:
         if not path.exists():
             if is_file:
                 path.write_text(file_content.strip())
             else:
                 path.mkdir()
 
-    # Create .tach
-    tach_path = project_root / ".tach"
-    _create(tach_path)
+    # Create cache dir
+    cache_dir = get_cache_path(project_root)
+    _create(cache_dir)
     # Create info
-    info_path = tach_path / "tach.info"
+    info_path = cache_dir / "tach.info"
     _create(info_path, is_file=True, file_content=str(uuid.uuid4()))
     # Create .gitignore
     gitignore_content = """
@@ -27,9 +41,9 @@ def _create(path: Path, is_file: bool = False, file_content: str = "") -> None:
 # gitignore all content, including this .gitignore
 *
     """
-    gitignore_path = tach_path / ".gitignore"
+    gitignore_path = cache_dir / ".gitignore"
     _create(gitignore_path, is_file=True, file_content=gitignore_content)
     # Create version
-    version_path = tach_path / ".latest-version"
+    version_path = cache_dir / ".latest-version"
     _create(version_path, is_file=True, file_content=__version__)
-    return Path(tach_path)
+    return Path(cache_dir)

python/tests/test_cache.py

@@ -4,29 +4,29 @@
 from unittest.mock import patch
 
 from tach.cache.access import get_latest_version, get_uid
-from tach.cache.setup import resolve_dot_tach
+from tach.cache.setup import get_cache_path, resolve_cache_path
 
 
-def test_resolve_dot_tach(tmp_path):
+def test_resolve_cache_path(tmp_path):
     project_path = tmp_path / "project"
     project_path.mkdir(parents=True, exist_ok=True)
     version = "1.0.0"
 
     with patch("tach.cache.setup.__version__", version):
-        result = resolve_dot_tach(project_path)
+        result = resolve_cache_path(project_path)
 
-    tach_path = project_path / ".tach"
-    assert tach_path.exists()
-    assert (tach_path / "tach.info").exists()
-    assert (tach_path / "tach.info").read_text().strip() != ""
-    assert (tach_path / ".gitignore").exists()
-    assert (tach_path / ".latest-version").exists()
-    assert (tach_path / ".latest-version").read_text().strip() == version
-    assert result == tach_path
+    cache_path = get_cache_path(project_path)
+    assert cache_path.exists()
+    assert (cache_path / "tach.info").exists()
+    assert (cache_path / "tach.info").read_text().strip() != ""
+    assert (cache_path / ".gitignore").exists()
+    assert (cache_path / ".latest-version").exists()
+    assert (cache_path / ".latest-version").read_text().strip() == version
+    assert result == cache_path
 
 
-@patch("tach.cache.access.resolve_dot_tach")
-def test_get_uid(mock_resolve_dot_tach, tmp_path):
+@patch("tach.cache.access.resolve_cache_path")
+def test_get_uid(mock_resolve_cache_path, tmp_path):
     project_path = tmp_path / "project"
     tach_info_path = project_path / ".tach" / "tach.info"
     tach_info_path.parent.mkdir(parents=True, exist_ok=True)
@@ -39,7 +39,8 @@ def test_get_uid(mock_resolve_dot_tach, tmp_path):
 
 def test_get_latest_version(tmp_path):
     project_path = tmp_path / "project"
-    latest_version_path = project_path / ".tach" / ".latest-version"
+    cache_path = get_cache_path(project_path)
+    latest_version_path = cache_path / ".latest-version"
     latest_version_path.parent.mkdir(parents=True, exist_ok=True)
     version = "1.0.0"
     latest_version_path.write_text(version)

src/cache.rs

@@ -36,7 +36,8 @@ impl FromIterator<u8> for CacheKey {
     }
 }
 
-static CACHE_DIR: &str = ".tach";
+static ENV_KEY_CACHE_DIR: &str = "TACH_CACHE_DIR";
+static DEFAULT_CACHE_DIR: &str = ".tach";
 
 pub type ComputationCacheValue = (Vec<(u8, String)>, u8);
 
@@ -48,7 +49,12 @@ fn build_computation_cache<P: AsRef<Path>>(
             .set_disk_directory(
                 project_root
                     .as_ref()
-                    .join(CACHE_DIR)
+                    .join(
+                        match env::var(ENV_KEY_CACHE_DIR) {
+                            Ok(env_value) => env_value,
+                            Err() => DEFAULT_CACHE_DIR,
+                        }
+                    )
                     .join("computation-cache"),
             )
             .build()?,