Purge rustwide cargo caches when we get a new nightly version

Author: syphar

src/build_queue.rs

@@ -266,13 +266,27 @@ impl BuildQueue {
                 .map(|r| PackageKind::Registry(r.as_str()))
                 .unwrap_or(PackageKind::CratesIo);
 
-            if let Err(err) = builder
+            match builder
                 .update_toolchain()
                 .context("Updating toolchain failed, locking queue")
             {
-                report_error(&err);
-                self.lock()?;
-                return Err(err);
+                Err(err) => {
+                    report_error(&err);
+                    self.lock()?;
+                    return Err(err);
+                }
+                Ok(true) => {
+                    // toolchain has changed, purge caches
+                    if let Err(err) = builder
+                        .purge_caches()
+                        .context("purging rustwide caches failed, locking queue")
+                    {
+                        report_error(&err);
+                        self.lock()?;
+                        return Err(err);
+                    }
+                }
+                Ok(false) => {}
             }
 
             builder.build_package(&krate.name, &krate.version, kind)?;

src/docbuilder/rustwide_builder.rs

@@ -98,7 +98,14 @@ impl RustwideBuilder {
             .enable_networking(limits.networking())
     }
 
-    pub fn update_toolchain(&mut self) -> Result<()> {
+    pub fn purge_caches(&self) -> Result<()> {
+        self.workspace
+            .purge_all_caches()
+            .map_err(FailureError::compat)?;
+        Ok(())
+    }
+
+    pub fn update_toolchain(&mut self) -> Result<bool> {
         // Ignore errors if detection fails.
         let old_version = self.detect_rustc_version().ok();
 
@@ -157,11 +164,12 @@ impl RustwideBuilder {
         }
 
         self.rustc_version = self.detect_rustc_version()?;
-        if old_version.as_deref() != Some(&self.rustc_version) {
+
+        let has_changed = old_version.as_deref() != Some(&self.rustc_version);
+        if has_changed {
             self.add_essential_files()?;
         }
-
-        Ok(())
+        Ok(has_changed)
     }
 
     fn detect_rustc_version(&self) -> Result<String> {