feat(mctx)!: configure separate state and cache directories by twitchyliquid64 · Pull Request #292 · gominimal/minimal

twitchyliquid64 · 2026-06-02T21:08:32Z

Under Minimal One, we are going to have minimal state (like sandboxes, sessions etc) live in one directory (typically $XDG_STATE_DIR/minimal or $HOME/.local/state/minimal) and cached objects (like the artifact cache, fetched sources etc) live in another ($XDG_CACHE_DIR/minimal or $HOME/.local/cache/minimal). This separation better follows the XDG specification.

The default remains the same when the directories are not specified via the mctx::ConfigBuilder. We should pick a date in the future to make a hard switch.

Summary by CodeRabbit

Refactor
- Separated state and cache storage into distinct base directories and updated local built-artifact cache handling. This clarifies where state vs. cache data live, improves isolation of cached artifacts, and makes cache initialization and access more predictable.

coderabbitai · 2026-06-02T21:08:44Z

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 2cc7e79d-3083-48b8-a339-40223117fc48

📥 Commits

Reviewing files that changed from the base of the PR and between f79d700 and a77c944.

📒 Files selected for processing (3)

crates/mctx/src/config.rs
crates/mctx/src/env.rs
crates/mctx/src/lib.rs

🚧 Files skipped from review as they are similar to previous changes (2)

crates/mctx/src/lib.rs
crates/mctx/src/config.rs

📝 Walkthrough

Walkthrough

The PR splits Config's single minimal directory into two bases: minimal_state_dir (state paths) and minimal_cache_dir (cache paths). Builder, Config, path helpers, Context cache initialization/accessor, a test, and a doc comment are updated to use the new layout.

Changes

Directory Layout Split

Layer / File(s)	Summary
Config builder and struct directory split `crates/mctx/src/config.rs`	ConfigBuilder fields and Config struct now use `minimal_state_dir` and `minimal_cache_dir`. Adds `with_cache_dir()` and updates `with_state_dir()` to target `minimal_state_dir`.
Config initialization and round-trip conversion `crates/mctx/src/config.rs`	`ConfigBuilder::build()` initializes both minimal bases; `Config::into_builder()` reconstructs the builder preserving both fields.
Config directory helper methods `crates/mctx/src/config.rs`	Path helpers refactored: state paths (`builds_base_dir`, `state_base_dir`, `task_base_dir`) join from `minimal_state_dir`; cache paths (`built_cache_dir`, `downloads_dir`, `vcs_dir`, `index_dir`, `stdlib_dir`, `layer_cache_dir`) join from `minimal_cache_dir`. `cache_dir()` removed in favor of `built_cache_dir()`.
Context cache initialization and accessors `crates/mctx/src/lib.rs`	`Context::sub_setup` creates `built_cache_dir()` and initializes `Cache` with it. `Context::cache_base_dir()` returns `built_cache_dir()`.
Test adjustment and minimal_file() documentation `crates/mctx/src/env.rs`, `crates/mctx/src/lib.rs`	`env_channel_add_session` test uses `ctx.cache.temp_dir()` for rootfs and adds a pre-install assertion; `Context::minimal_file()` doc comment clarified.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Poem

🐰 Two burrows now, neatly aligned,
State for the roots, cache for the rind,
Builder hops, fields split in two,
Context finds the cache anew,
A little change, tidy and kind.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The pull request title accurately and specifically describes the main change: introducing separate configuration for state and cache directories in the mctx crate.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

crates/mctx/src/config.rs (1)

163-179: ⚠️ Potential issue | 🔴 Critical | ⚡ Quick win

Fix the fallback path: tilde won't expand in PathBuf.

The fallback PathBuf::from("~/.cache") (lines 165-166, 177-178) creates a path with a literal ~ character, not the user's home directory. Shell tilde expansion doesn't occur in PathBuf::from(). This will create a directory named ~ relative to the current directory, causing unexpected behavior.

The TODO comments at lines 159 and 171 show the correct approach using dirs::home_dir().

🐛 Proposed fix using dirs::home_dir()

             minimal_state_dir: self.minimal_state_dir.unwrap_or_else(|| {
                 dirs::cache_dir()
-                    .unwrap_or_else(|| PathBuf::from("~/.cache"))
+                    .unwrap_or_else(|| dirs::home_dir().unwrap_or_else(|| PathBuf::from(".")).join(".cache"))
                     .join("minimal")
             }),

             minimal_cache_dir: self.minimal_cache_dir.unwrap_or_else(|| {
                 dirs::cache_dir()
-                    .unwrap_or_else(|| PathBuf::from("~/.cache"))
+                    .unwrap_or_else(|| dirs::home_dir().unwrap_or_else(|| PathBuf::from(".")).join(".cache"))
                     .join("minimal")
             }),

Note: Added a final fallback to . (current directory) in case both dirs::cache_dir() and dirs::home_dir() return None, which can happen in unusual environments.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@crates/mctx/src/config.rs` around lines 163 - 179, The fallback
PathBuf::from("~/.cache") used when building minimal_state_dir and
minimal_cache_dir is incorrect because tilde isn't expanded; replace that
fallback with logic that uses dirs::home_dir() to construct
home_dir.join(".cache") and, if both dirs::cache_dir() and dirs::home_dir() are
None, fall back to PathBuf::from(".") (current directory); update the
expressions for minimal_state_dir and minimal_cache_dir (referencing
minimal_state_dir, minimal_cache_dir, dirs::cache_dir(), dirs::home_dir(), and
the existing unwrap_or_else closures) to build the cache path via home_dir
instead of the literal "~/.cache".

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Outside diff comments:
In `@crates/mctx/src/config.rs`:
- Around line 163-179: The fallback PathBuf::from("~/.cache") used when building
minimal_state_dir and minimal_cache_dir is incorrect because tilde isn't
expanded; replace that fallback with logic that uses dirs::home_dir() to
construct home_dir.join(".cache") and, if both dirs::cache_dir() and
dirs::home_dir() are None, fall back to PathBuf::from(".") (current directory);
update the expressions for minimal_state_dir and minimal_cache_dir (referencing
minimal_state_dir, minimal_cache_dir, dirs::cache_dir(), dirs::home_dir(), and
the existing unwrap_or_else closures) to build the cache path via home_dir
instead of the literal "~/.cache".

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: da113a19-145b-4c1c-80c2-4f09c992a6ca

📥 Commits

Reviewing files that changed from the base of the PR and between 105e63d and f79d700.

📒 Files selected for processing (2)

crates/mctx/src/config.rs
crates/mctx/src/lib.rs

norrietaylor

LGTM

twitchyliquid64 requested review from 0chroma and evanspearman June 2, 2026 21:08

coderabbitai Bot reviewed Jun 2, 2026

View reviewed changes

feat(mctx): configure separate state and cache directories

a77c944

twitchyliquid64 force-pushed the tom/update branch from f79d700 to a77c944 Compare June 2, 2026 21:33

norrietaylor approved these changes Jun 2, 2026

View reviewed changes

twitchyliquid64 merged commit 6e145ba into main Jun 2, 2026
9 checks passed

twitchyliquid64 deleted the tom/update branch June 2, 2026 22:31

coderabbitai Bot mentioned this pull request Jun 8, 2026

chore(mctx): set cache dir to avoid /tmp mount settings failing tests #370

Merged

coderabbitai Bot mentioned this pull request Jul 2, 2026

feat!: coalesce default dir computation across crates #619

Merged

gominimal-aw-bot Bot mentioned this pull request Jul 31, 2026

fix: correct --minimal-dir help to name the state dir and per-platform defaults #1136

Merged

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feat(mctx)!: configure separate state and cache directories - #292

feat(mctx)!: configure separate state and cache directories#292
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twitchyliquid64 commented Jun 2, 2026 •

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