refactor rustc_cfg to be more inline with docs/dev/style.md

crates/project-model/src/rustc_cfg.rs

@@ -2,15 +2,21 @@
 
 use std::process::Command;
 
+use anyhow::Context;
 use rustc_hash::FxHashMap;
 
 use crate::{cfg_flag::CfgFlag, utf8_stdout, ManifestPath, Sysroot};
 
+pub(crate) enum Config<'a> {
+    Cargo(&'a ManifestPath),
+    Explicit(&'a Sysroot),
+    Discover,
+}
+
 pub(crate) fn get(
-    cargo_toml: Option<&ManifestPath>,
-    sysroot: Option<&Sysroot>,
     target: Option<&str>,
     extra_env: &FxHashMap<String, String>,
+    config: Config<'_>,
 ) -> Vec<CfgFlag> {
     let _p = profile::span("rustc_cfg::get");
     let mut res = Vec::with_capacity(6 * 2 + 1);
@@ -26,64 +32,68 @@ pub(crate) fn get(
     // Add miri cfg, which is useful for mir eval in stdlib
     res.push(CfgFlag::Atom("miri".into()));
 
-    match get_rust_cfgs(cargo_toml, sysroot, target, extra_env) {
+    let rustc_cfgs = get_rust_cfgs(target, extra_env, config);
+
+    let rustc_cfgs = match rustc_cfgs {
+        Ok(cfgs) => cfgs,
+        Err(e) => {
+            tracing::error!(?e, "failed to get rustc cfgs");
+            return res;
+        }
+    };
+
+    let rustc_cfgs =
+        rustc_cfgs.lines().map(|it| it.parse::<CfgFlag>()).collect::<Result<Vec<_>, _>>();
+
+    match rustc_cfgs {
         Ok(rustc_cfgs) => {
-            tracing::debug!(
-                "rustc cfgs found: {:?}",
-                rustc_cfgs
-                    .lines()
-                    .map(|it| it.parse::<CfgFlag>().map(|it| it.to_string()))
-                    .collect::<Vec<_>>()
-            );
-            res.extend(rustc_cfgs.lines().filter_map(|it| it.parse().ok()));
+            tracing::debug!(?rustc_cfgs, "rustc cfgs found");
+            res.extend(rustc_cfgs);
+        }
+        Err(e) => {
+            tracing::error!(?e, "failed to get rustc cfgs")
         }
-        Err(e) => tracing::error!("failed to get rustc cfgs: {e:?}"),
     }
 
     res
 }
 
 fn get_rust_cfgs(
-    cargo_toml: Option<&ManifestPath>,
-    sysroot: Option<&Sysroot>,
     target: Option<&str>,
     extra_env: &FxHashMap<String, String>,
+    config: Config<'_>,
 ) -> anyhow::Result<String> {
-    if let Some(cargo_toml) = cargo_toml {
-        let mut cargo_config = Command::new(toolchain::cargo());
-        cargo_config.envs(extra_env);
-        cargo_config
-            .current_dir(cargo_toml.parent())
-            .args(["rustc", "-Z", "unstable-options", "--print", "cfg"])
-            .env("RUSTC_BOOTSTRAP", "1");
-        if let Some(target) = target {
-            cargo_config.args(["--target", target]);
-        }
-        match utf8_stdout(cargo_config) {
-            Ok(it) => return Ok(it),
-            Err(e) => tracing::debug!("{e:?}: falling back to querying rustc for cfgs"),
-        }
-    }
+    let mut cmd = match config {
+        Config::Cargo(cargo_toml) => {
+            let mut cmd = Command::new(toolchain::cargo());
+            cmd.envs(extra_env);
+            cmd.current_dir(cargo_toml.parent())
+                .args(["rustc", "-Z", "unstable-options", "--print", "cfg"])
+                .env("RUSTC_BOOTSTRAP", "1");
+            if let Some(target) = target {
+                cmd.args(["--target", target]);
+            }
 
-    let rustc = match sysroot {
-        Some(sysroot) => {
-            let rustc = sysroot.discover_rustc()?.into();
-            tracing::debug!(?rustc, "using rustc from sysroot");
-            rustc
+            return utf8_stdout(cmd).context("Unable to run `cargo rustc`");
+        }
+        Config::Explicit(sysroot) => {
+            let rustc: std::path::PathBuf = sysroot.discover_rustc()?.into();
+            tracing::debug!(?rustc, "using explicit rustc from sysroot");
+            Command::new(rustc)
         }
-        None => {
+        Config::Discover => {
             let rustc = toolchain::rustc();
             tracing::debug!(?rustc, "using rustc from env");
-            rustc
+            Command::new(rustc)
         }
     };
 
-    // using unstable cargo features failed, fall back to using plain rustc
-    let mut cmd = Command::new(rustc);
     cmd.envs(extra_env);
     cmd.args(["--print", "cfg", "-O"]);
     if let Some(target) = target {
         cmd.args(["--target", target]);
     }
-    utf8_stdout(cmd)
+
+    let out = utf8_stdout(cmd).context("Unable to run `rustc`")?;
+    Ok(out)
 }

crates/project-model/src/workspace.rs

@@ -280,10 +280,9 @@ impl ProjectWorkspace {
                 });
 
                 let rustc_cfg = rustc_cfg::get(
-                    Some(&cargo_toml),
-                    None,
                     config.target.as_deref(),
                     &config.extra_env,
+                    rustc_cfg::Config::Cargo(cargo_toml),
                 );
 
                 let cfg_overrides = config.cfg_overrides.clone();
@@ -335,11 +334,18 @@ impl ProjectWorkspace {
             }
             (None, None) => Err(None),
         };
-        if let Ok(sysroot) = &sysroot {
-            tracing::info!(src_root = %sysroot.src_root(), root = %sysroot.root(), "Using sysroot");
-        }
+        let config = match &sysroot {
+            Ok(sysroot) => {
+                tracing::debug!(src_root = %sysroot.src_root(), root = %sysroot.root(), "Using sysroot");
+                rustc_cfg::Config::Explicit(sysroot)
+            }
+            Err(_) => {
+                tracing::debug!("discovering sysroot");
+                rustc_cfg::Config::Discover
+            }
+        };
 
-        let rustc_cfg = rustc_cfg::get(None, sysroot.as_ref().ok(), target, extra_env);
+        let rustc_cfg = rustc_cfg::get(target, extra_env, config);
         ProjectWorkspace::Json { project: project_json, sysroot, rustc_cfg, toolchain }
     }
 
@@ -361,10 +367,18 @@ impl ProjectWorkspace {
             }
             None => Err(None),
         };
-        if let Ok(sysroot) = &sysroot {
-            tracing::info!(src_root = %sysroot.src_root(), root = %sysroot.root(), "Using sysroot");
-        }
-        let rustc_cfg = rustc_cfg::get(None, sysroot.as_ref().ok(), None, &Default::default());
+        let rustc_config = match &sysroot {
+            Ok(sysroot) => {
+                tracing::info!(src_root = %sysroot.src_root(), root = %sysroot.root(), "Using sysroot");
+                rustc_cfg::Config::Explicit(sysroot)
+            }
+            Err(_) => {
+                tracing::info!("discovering sysroot");
+                rustc_cfg::Config::Discover
+            }
+        };
+
+        let rustc_cfg = rustc_cfg::get(None, &FxHashMap::default(), rustc_config);
         Ok(ProjectWorkspace::DetachedFiles { files: detached_files, sysroot, rustc_cfg })
     }
 
@@ -758,9 +772,14 @@ fn project_json_to_crate_graph(
                 let env = env.clone().into_iter().collect();
 
                 let target_cfgs = match target.as_deref() {
-                    Some(target) => cfg_cache
-                        .entry(target)
-                        .or_insert_with(|| rustc_cfg::get(None, sysroot, Some(target), extra_env)),
+                    Some(target) => cfg_cache.entry(target).or_insert_with(|| {
+                        let rustc_cfg = match sysroot {
+                            Some(sysroot) => rustc_cfg::Config::Explicit(sysroot),
+                            None => rustc_cfg::Config::Discover,
+                        };
+
+                        rustc_cfg::get(Some(target), extra_env, rustc_cfg)
+                    }),
                     None => &rustc_cfg,
                 };