crates: add the Crate::purge_from_cache method

Author: pietroalbini

CHANGELOG.md

@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - New method `WorkspaceBuilder::fetch_registry_index_during_builds` to enable
   or disable fetching the registry's index during each build. The method is
   only available when the `unstable` rustwide feature is enabled.
+- New method `Crate::purge_from_cache` to remove the cached copy of a crate.
 
 ### Changed
 

src/crates/cratesio.rs

@@ -59,6 +59,14 @@ impl CrateTrait for CratesIOCrate {
         Ok(())
     }
 
+    fn purge_from_cache(&self, workspace: &Workspace) -> Result<(), Error> {
+        let path = self.cache_path(workspace);
+        if path.exists() {
+            std::fs::remove_file(&path)?;
+        }
+        Ok(())
+    }
+
     fn copy_source_to(&self, workspace: &Workspace, dest: &Path) -> Result<(), Error> {
         let cached = self.cache_path(workspace);
         let mut file = File::open(cached)?;

src/crates/git.rs

@@ -118,6 +118,14 @@ impl CrateTrait for GitRepo {
         }
     }
 
+    fn purge_from_cache(&self, workspace: &Workspace) -> Result<(), Error> {
+        let path = self.cached_path(workspace);
+        if path.exists() {
+            remove_dir_all::remove_dir_all(&path)?;
+        }
+        Ok(())
+    }
+
     fn copy_source_to(&self, workspace: &Workspace, dest: &Path) -> Result<(), Error> {
         Command::new(workspace, "git")
             .args(&["clone"])

src/crates/local.rs

@@ -21,6 +21,11 @@ impl CrateTrait for Local {
         Ok(())
     }
 
+    fn purge_from_cache(&self, _workspace: &Workspace) -> Result<(), Error> {
+        // There is no cache to purge for a local crate.
+        Ok(())
+    }
+
     fn copy_source_to(&self, _workspace: &Workspace, dest: &Path) -> Result<(), Error> {
         info!(
             "copying local crate from {} to {}",

src/crates/mod.rs

@@ -10,6 +10,7 @@ use std::path::Path;
 
 trait CrateTrait: std::fmt::Display {
     fn fetch(&self, workspace: &Workspace) -> Result<(), Error>;
+    fn purge_from_cache(&self, workspace: &Workspace) -> Result<(), Error>;
     fn copy_source_to(&self, workspace: &Workspace, dest: &Path) -> Result<(), Error>;
 }
 
@@ -47,6 +48,11 @@ impl Crate {
         self.as_trait().fetch(workspace)
     }
 
+    /// Remove the cached copy of this crate. The method will do nothing if the crate isn't cached.
+    pub fn purge_from_cache(&self, workspace: &Workspace) -> Result<(), Error> {
+        self.as_trait().purge_from_cache(workspace)
+    }
+
     /// Get this crate's git commit. This method is best-effort, and currently works just for git
     /// crates. If the commit can't be retrieved `None` will be returned.
     pub fn git_commit(&self, workspace: &Workspace) -> Option<String> {