Fix rustfmt during builds by reading edition from manifest

rls/src/actions/mod.rs

@@ -23,6 +23,7 @@ use crate::project_model::{ProjectModel, RacerFallbackModel, RacerProjectModel};
 use crate::server::Output;
 
 use std::collections::{HashMap, HashSet};
+use std::convert::TryFrom;
 use std::io;
 use std::path::{Path, PathBuf};
 use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering};
@@ -281,12 +282,21 @@ impl InitActionContext {
     fn file_edition(&self, file: PathBuf) -> Option<Edition> {
         let files_to_crates = self.file_to_crates.lock().unwrap();
 
-        let editions: HashSet<_> = files_to_crates.get(&file)?.iter().map(|c| c.edition).collect();
+        let editions: HashSet<_> = files_to_crates
+            .get(&file)
+            .map(|crates| crates.iter().map(|c| c.edition).collect())
+            .unwrap_or_default();
 
         let mut iter = editions.into_iter();
         match (iter.next(), iter.next()) {
             (ret @ Some(_), None) => ret,
-            _ => None,
+            (Some(_), Some(_)) => None,
+            _ => {
+                // fall back on checking the root manifest for package edition
+                let manifest_path =
+                    cargo::util::important_paths::find_root_manifest_for_wd(&file).ok()?;
+                edition_from_manifest(manifest_path)
+            }
         }
     }
 
@@ -425,6 +435,24 @@ impl InitActionContext {
     }
 }
 
+/// Read package edition from the Cargo manifest
+fn edition_from_manifest<P: AsRef<Path>>(manifest_path: P) -> Option<Edition> {
+    #[derive(Debug, serde::Deserialize)]
+    struct Manifest {
+        package: Package,
+    }
+    #[derive(Debug, serde::Deserialize)]
+    struct Package {
+        edition: Option<String>,
+    }
+
+    let manifest: Manifest = toml::from_str(&std::fs::read_to_string(manifest_path).ok()?).ok()?;
+    match manifest.package.edition {
+        Some(edition) => Edition::try_from(edition.as_str()).ok(),
+        None => Some(Edition::default()),
+    }
+}
+
 /// Some notifications come with sequence numbers, we check that these are in
 /// order. However, clients might be buggy about sequence numbers so we do cope
 /// with them being wrong.
@@ -662,4 +690,28 @@ mod test {
         assert!(!watch.is_relevant_save_doc(&did_save("file:///c:/some/dir/inner/Cargo.lock")));
         assert!(!watch.is_relevant_save_doc(&did_save("file:///c:/Cargo.toml")));
     }
+
+    #[test]
+    fn explicit_edition_from_manifest() -> Result<(), std::io::Error> {
+        use std::{fs::File, io::Write};
+
+        let dir = tempfile::tempdir()?;
+
+        let manifest_path = {
+            let path = dir.path().join("Cargo.toml");
+            let mut m = File::create(&path)?;
+            writeln!(
+                m,
+                "[package]\n\
+                 name = \"foo\"\n\
+                 version = \"1.0.0\"\n\
+                 edition = \"2018\""
+            )?;
+            path
+        };
+
+        assert_eq!(edition_from_manifest(manifest_path), Some(Edition::Edition2018));
+
+        Ok(())
+    }
 }

rls/src/build/plan.rs

@@ -242,3 +242,15 @@ impl Default for Edition {
         Edition::Edition2015
     }
 }
+
+impl std::convert::TryFrom<&str> for Edition {
+    type Error = &'static str;
+
+    fn try_from(val: &str) -> Result<Self, Self::Error> {
+        Ok(match val {
+            "2015" => Edition::Edition2015,
+            "2018" => Edition::Edition2018,
+            _ => return Err("unknown"),
+        })
+    }
+}