Stabilize automatic garbage collection.

src/cargo/core/gc.rs

@@ -49,9 +49,6 @@ const DEFAULT_AUTO_FREQUENCY: &str = "1 day";
 /// It should be cheap to call this multiple times (subsequent calls are
 /// ignored), but try not to abuse that.
 pub fn auto_gc(gctx: &GlobalContext) {
-    if !gctx.cli_unstable().gc {
-        return;
-    }
     if !gctx.network_allowed() {
         // As a conservative choice, auto-gc is disabled when offline. If the
         // user is indefinitely offline, we don't want to delete things they
@@ -174,49 +171,74 @@ impl GcOpts {
         let config = gctx
             .get::<Option<GlobalCleanConfig>>("cache.global-clean")?
             .unwrap_or_default();
-        self.update_for_auto_gc_config(&config)
+        self.update_for_auto_gc_config(&config, gctx.cli_unstable().gc)
     }
 
-    fn update_for_auto_gc_config(&mut self, config: &GlobalCleanConfig) -> CargoResult<()> {
+    fn update_for_auto_gc_config(
+        &mut self,
+        config: &GlobalCleanConfig,
+        unstable_allowed: bool,
+    ) -> CargoResult<()> {
+        macro_rules! config_default {
+            ($config:expr, $field:ident, $default:expr, $unstable_allowed:expr) => {
+                if !unstable_allowed {
+                    // These config options require -Zgc
+                    $default
+                } else {
+                    $config.$field.as_deref().unwrap_or($default)
+                }
+            };
+        }
+
         self.max_src_age = newer_time_span_for_config(
             self.max_src_age,
-            "cache.global-clean.max-src-age",
-            config
-                .max_src_age
-                .as_deref()
-                .unwrap_or(DEFAULT_MAX_AGE_EXTRACTED),
+            "gc.auto.max-src-age",
+            config_default!(
+                config,
+                max_src_age,
+                DEFAULT_MAX_AGE_EXTRACTED,
+                unstable_allowed
+            ),
         )?;
         self.max_crate_age = newer_time_span_for_config(
             self.max_crate_age,
-            "cache.global-clean.max-crate-age",
-            config
-                .max_crate_age
-                .as_deref()
-                .unwrap_or(DEFAULT_MAX_AGE_DOWNLOADED),
+            "gc.auto.max-crate-age",
+            config_default!(
+                config,
+                max_crate_age,
+                DEFAULT_MAX_AGE_DOWNLOADED,
+                unstable_allowed
+            ),
         )?;
         self.max_index_age = newer_time_span_for_config(
             self.max_index_age,
-            "cache.global-clean.max-index-age",
-            config
-                .max_index_age
-                .as_deref()
-                .unwrap_or(DEFAULT_MAX_AGE_DOWNLOADED),
+            "gc.auto.max-index-age",
+            config_default!(
+                config,
+                max_index_age,
+                DEFAULT_MAX_AGE_DOWNLOADED,
+                unstable_allowed
+            ),
         )?;
         self.max_git_co_age = newer_time_span_for_config(
             self.max_git_co_age,
-            "cache.global-clean.max-git-co-age",
-            config
-                .max_git_co_age
-                .as_deref()
-                .unwrap_or(DEFAULT_MAX_AGE_EXTRACTED),
+            "gc.auto.max-git-co-age",
+            config_default!(
+                config,
+                max_git_co_age,
+                DEFAULT_MAX_AGE_EXTRACTED,
+                unstable_allowed
+            ),
         )?;
         self.max_git_db_age = newer_time_span_for_config(
             self.max_git_db_age,
-            "cache.global-clean.max-git-db-age",
-            config
-                .max_git_db_age
-                .as_deref()
-                .unwrap_or(DEFAULT_MAX_AGE_DOWNLOADED),
+            "gc.auto.max-git-db-age",
+            config_default!(
+                config,
+                max_git_db_age,
+                DEFAULT_MAX_AGE_DOWNLOADED,
+                unstable_allowed
+            ),
         )?;
         Ok(())
     }
@@ -255,9 +277,6 @@ impl<'a, 'gctx> Gc<'a, 'gctx> {
     /// This returns immediately without doing work if garbage collection has
     /// been performed recently (since `cache.auto-clean-frequency`).
     fn auto(&mut self, clean_ctx: &mut CleanContext<'gctx>) -> CargoResult<()> {
-        if !self.gctx.cli_unstable().gc {
-            return Ok(());
-        }
         let freq = self
             .gctx
             .get::<Option<String>>("cache.auto-clean-frequency")?;
@@ -274,7 +293,7 @@ impl<'a, 'gctx> Gc<'a, 'gctx> {
             .unwrap_or_default();
 
         let mut gc_opts = GcOpts::default();
-        gc_opts.update_for_auto_gc_config(&config)?;
+        gc_opts.update_for_auto_gc_config(&config, self.gctx.cli_unstable().gc)?;
         self.gc(clean_ctx, &gc_opts)?;
         if !clean_ctx.dry_run {
             self.global_cache_tracker.set_last_auto_gc()?;

src/doc/src/reference/config.md

@@ -95,6 +95,9 @@ ENV_VAR_NAME_3 = { value = "relative/path", relative = true }
 [future-incompat-report]
 frequency = 'always' # when to display a notification about a future incompat report
 
+[cache]
+auto-clean-frequency = "1 day"   # How often to perform automatic cache cleaning
+
 [cargo-new]
 vcs = "none"              # VCS to use ('git', 'hg', 'pijul', 'fossil', 'none')
 
@@ -664,6 +667,41 @@ Controls how often we display a notification to the terminal when a future incom
 * `always` (default): Always display a notification when a command (e.g. `cargo build`) produces a future incompat report
 * `never`: Never display a notification
 
+### `[cache]`
+
+The `[cache]` table defines settings for cargo's caches.
+
+#### Global caches
+
+When running `cargo` commands, Cargo will automatically track which files you are using within the global cache.
+Periodically, Cargo will delete files that have not been used for some period of time.
+It will delete files that have to be downloaded from the network if they have not been used in 3 months. Files that can be generated without network access will be deleted if they have not been used in 1 month.
+
+The automatic deletion of files only occurs when running commands that are already doing a significant amount of work, such as all of the build commands (`cargo build`, `cargo test`, `cargo check`, etc.), and `cargo fetch`.
+
+Automatic deletion is disabled if cargo is offline such as with `--offline` or `--frozen` to avoid deleting artifacts that may need to be used if you are offline for a long period of time.
+
+> **Note**: This tracking is currently only implemented for the global cache in Cargo's home directory.
+> This includes registry indexes and source files downloaded from registries and git dependencies.
+> Support for tracking build artifacts is not yet implemented, and tracked in [cargo#13136](https://github.com/rust-lang/cargo/issues/13136).
+>
+> Additionally, there is an unstable feature to support *manually* triggering cache cleaning, and to further customize the configuration options.
+> See the [Unstable chapter](unstable.md#gc) for more information.
+
+#### `cache.auto-clean-frequency`
+* Type: string
+* Default: `"1 day"`
+* Environment: `CARGO_CACHE_AUTO_CLEAN_FREQUENCY`
+
+This option defines how often Cargo will automatically delete unused files in the global cache.
+This does *not* define how old the files must be, those thresholds are described [above](#global-caches).
+
+It supports the following settings:
+
+* `"never"` --- Never deletes old files.
+* `"always"` --- Checks to delete old files every time Cargo runs.
+* An integer followed by "seconds", "minutes", "hours", "days", "weeks", or "months" --- Checks to delete old files at most the given time frame.
+
 ### `[http]`
 
 The `[http]` table defines settings for HTTP behavior. This includes fetching

src/doc/src/reference/environment-variables.md

@@ -99,6 +99,7 @@ In summary, the supported environment variables are:
 * `CARGO_BUILD_RUSTDOCFLAGS` --- Extra `rustdoc` flags, see [`build.rustdocflags`].
 * `CARGO_BUILD_INCREMENTAL` --- Incremental compilation, see [`build.incremental`].
 * `CARGO_BUILD_DEP_INFO_BASEDIR` --- Dep-info relative directory, see [`build.dep-info-basedir`].
+* `CARGO_CACHE_AUTO_CLEAN_FREQUENCY` --- Configures how often automatic cache cleaning runs, see [`cache.auto-clean-frequency`].
 * `CARGO_CARGO_NEW_VCS` --- The default source control system with [`cargo new`], see [`cargo-new.vcs`].
 * `CARGO_FUTURE_INCOMPAT_REPORT_FREQUENCY` --- How often we should generate a future incompat report notification, see [`future-incompat-report.frequency`].
 * `CARGO_HTTP_DEBUG` --- Enables HTTP debugging, see [`http.debug`].
@@ -163,6 +164,7 @@ In summary, the supported environment variables are:
 [`build.incremental`]: config.md#buildincremental
 [`build.dep-info-basedir`]: config.md#builddep-info-basedir
 [`doc.browser`]: config.md#docbrowser
+[`cache.auto-clean-frequency`]: config.md#cacheauto-clean-frequency
 [`cargo-new.name`]: config.md#cargo-newname
 [`cargo-new.email`]: config.md#cargo-newemail
 [`cargo-new.vcs`]: config.md#cargo-newvcs

src/doc/src/reference/unstable.md

@@ -1588,37 +1588,16 @@ This will not affect any hard-coded paths in the source code, such as in strings
 
 * Tracking Issue: [#12633](https://github.com/rust-lang/cargo/issues/12633)
 
-The `-Zgc` flag enables garbage-collection within cargo's global cache within the cargo home directory.
-This includes downloaded dependencies such as compressed `.crate` files, extracted `src` directories, registry index caches, and git dependencies.
-When `-Zgc` is present, cargo will track the last time any index and dependency was used,
-and then uses those timestamps to manually or automatically delete cache entries that have not been used for a while.
-
-```sh
-cargo build -Zgc
-```
-
-### Automatic garbage collection
-
-Automatic deletion happens on commands that are already doing a significant amount of work,
-such as all of the build commands (`cargo build`, `cargo test`, `cargo check`, etc.), and `cargo fetch`.
-The deletion happens just after resolution and packages have been downloaded.
-Automatic deletion is only done once per day (see `cache.auto-clean-frequency` to configure).
-Automatic deletion is disabled if cargo is offline such as with `--offline` or `--frozen` to avoid deleting artifacts that may need to be used if you are offline for a long period of time.
+The `-Zgc` flag is used to enable certain features related to garbage-collection of cargo's global cache within the cargo home directory.
 
 #### Automatic gc configuration
 
-The automatic gc behavior can be specified via a cargo configuration setting.
+The `-Zgc` flag will enable Cargo to read extra configuration options related to garbage collection.
 The settings available are:
 
 ```toml
 # Example config.toml file.
 
-# This table defines settings for cargo's caches.
-[cache]
-# The maximum frequency that automatic cleaning of the cache happens.
-# Can be "never" to disable, or "always" to run on every command.
-auto-clean-frequency = "1 day"
-
 # Sub-table for defining specific settings for cleaning the global cache.
 [cache.global-clean]
 # Anything older than this duration will be deleted in the source cache.
@@ -1633,9 +1612,13 @@ max-git-co-age = "1 month"
 max-git-db-age = "3 months"
 ```
 
+Note that the [`cache.auto-clean-frequency`] option was stabilized in Rust 1.88.
+
+[`cache.auto-clean-frequency`]: config.md#cacheauto-clean-frequency
+
 ### Manual garbage collection with `cargo clean`
 
-Manual deletion can be done with the `cargo clean gc` command.
+Manual deletion can be done with the `cargo clean gc -Zgc` command.
 Deletion of cache contents can be performed by passing one of the cache options:
 
 - `--max-src-age=DURATION` --- Deletes source cache files that have not been used since the given age.
@@ -1654,9 +1637,9 @@ A DURATION is specified in the form "N seconds/minutes/days/weeks/months" where
 A SIZE is specified in the form "N *suffix*" where *suffix* is B, kB, MB, GB, kiB, MiB, or GiB, and N is an integer or floating point number. If no suffix is specified, the number is the number of bytes.
 
 ```sh
-cargo clean gc
-cargo clean gc --max-download-age=1week
-cargo clean gc --max-git-size=0 --max-download-size=100MB
+cargo clean gc -Zgc
+cargo clean gc -Zgc --max-download-age=1week
+cargo clean gc -Zgc --max-git-size=0 --max-download-size=100MB
 ```
 
 ## open-namespaces
@@ -2166,3 +2149,7 @@ The 2024 edition has been stabilized in the 1.85 release.
 See the [`edition` field](manifest.md#the-edition-field) for more information on setting the edition.
 See [`cargo fix --edition`](../commands/cargo-fix.md) and [The Edition Guide](../../edition-guide/index.html) for more information on migrating existing projects.
 
+## Automatic garbage collection
+
+Support for automatically deleting old files was stabilized in Rust 1.88.
+More information can be found in the [config chapter](config.md#cache).