Prevent calling rustc_version::version_meta() multiple times

Cargo.toml

@@ -17,6 +17,7 @@ version = "0.3.3"
 [dependencies]
 cargo_metadata = "0.11"
 clap = "2.33"
+lazy_static = "1.4"
 regex = "1.3"
 rustc-cfg = "0.4"
 rustc-demangle = "0.1"

src/lib.rs

@@ -61,10 +61,10 @@ impl Context {
             // TODO: How will custom profiles impact this?
             if path == "debug" || path == "release" {
                 // Looks like this artifact was built for the host.
-                rustc_version::version_meta()?.host
+                rustc::version_meta()?.host.as_str().into()
             } else {
                 // The artifact
-                path.to_string()
+                path
             }
         } else {
             unreachable!();
@@ -76,7 +76,7 @@ impl Context {
     /// Get a context structure from a provided target flag, used when cargo
     /// was not used to build the binary.
     fn from_flag(metadata: Metadata, target_flag: Option<&str>) -> Result<Self> {
-        let host_target_name = rustc_version::version_meta()?.host;
+        let host_target_name = rustc::version_meta()?.host.as_str();
 
         // Get the "default" target override in .cargo/config.
         let mut config_target_name = None;
@@ -93,7 +93,7 @@ impl Context {
         // Find the actual target.
         let target_name = target_flag
             .or(config_target_name)
-            .unwrap_or(&host_target_name);
+            .unwrap_or(host_target_name);
 
         Self::from_target_name(target_name)
     }

src/rustc.rs

@@ -1,8 +1,41 @@
 use std::env;
+use std::error::Error;
+use std::fmt::{self, Debug, Display, Formatter};
 use std::path::PathBuf;
 use std::process::Command;
 
 use anyhow::Result;
+use rustc_version::VersionMeta;
+
+struct RefError<'a, T>(&'a T);
+
+impl<'a, T: Debug> Debug for RefError<'a, T> {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        Debug::fmt(self.0, f)
+    }
+}
+
+impl<'a, T: Display> Display for RefError<'a, T> {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        Display::fmt(self.0, f)
+    }
+}
+
+impl<'a, T: Error> Error for RefError<'a, T> {
+    fn source(&self) -> Option<&(dyn Error + 'static)> {
+        self.0.source()
+    }
+}
+
+lazy_static::lazy_static! {
+    static ref VERSION_META: Result<VersionMeta, rustc_version::Error> = rustc_version::version_meta();
+}
+
+pub fn version_meta() -> Result<&'static VersionMeta> {
+    VERSION_META
+        .as_ref()
+        .map_err(|error| RefError(error).into())
+}
 
 pub fn sysroot() -> Result<String> {
     let rustc = env::var_os("RUSTC").unwrap_or_else(|| "rustc".into());
@@ -17,7 +50,7 @@ pub fn rustlib() -> Result<PathBuf> {
     let mut pathbuf = PathBuf::from(sysroot);
     pathbuf.push("lib");
     pathbuf.push("rustlib");
-    pathbuf.push(rustc_version::version_meta()?.host); // TODO: Prevent calling rustc_version::version_meta() multiple times
+    pathbuf.push(&version_meta()?.host);
     pathbuf.push("bin");
     Ok(pathbuf)
 }