allow using null to unset an environment variable

this makes three changes:
- all callsites of `toolchain::command` are changed to use
  `command(path, extra_env)`, instead of manually adding the env after
  the fact.
- all `map<str, str>` are changed to `map<str, option<str>>`.
- `command` checks for None and calls `env_remove` if so.

this caught several places where environment variables weren't being
propagated:
- when running `rustc --print=target-libdir`
- when running `cargo rustc -- --print=target-spec-json`
- when running the custom DiscoverLinkedProjects config. I *think* this
  is for use with non-cargo build systems, so I didn't change it.

crates/rust-analyzer/src/config.rs

@@ -602,7 +602,7 @@ config_data! {
         cargo_extraArgs: Vec<String> = vec![],
         /// Extra environment variables that will be set when running cargo, rustc
         /// or other commands within the workspace. Useful for setting RUSTFLAGS.
-        cargo_extraEnv: FxHashMap<String, String> = FxHashMap::default(),
+        cargo_extraEnv: FxHashMap<String, Option<String>> = FxHashMap::default(),
         /// List of features to activate.
         ///
         /// Set this to `"all"` to pass `--all-features` to cargo.
@@ -652,7 +652,7 @@ config_data! {
         check_extraArgs | checkOnSave_extraArgs: Vec<String>             = vec![],
         /// Extra environment variables that will be set when running `cargo check`.
         /// Extends `#rust-analyzer.cargo.extraEnv#`.
-        check_extraEnv | checkOnSave_extraEnv: FxHashMap<String, String> = FxHashMap::default(),
+        check_extraEnv | checkOnSave_extraEnv: FxHashMap<String, Option<String>> = FxHashMap::default(),
         /// List of features to activate. Defaults to
         /// `#rust-analyzer.cargo.features#`.
         ///
@@ -1879,7 +1879,10 @@ impl Config {
         self.cargo_extraArgs(source_root)
     }
 
-    pub fn extra_env(&self, source_root: Option<SourceRootId>) -> &FxHashMap<String, String> {
+    pub fn extra_env(
+        &self,
+        source_root: Option<SourceRootId>,
+    ) -> &FxHashMap<String, Option<String>> {
         self.cargo_extraEnv(source_root)
     }
 
@@ -1889,7 +1892,10 @@ impl Config {
         extra_args
     }
 
-    pub fn check_extra_env(&self, source_root: Option<SourceRootId>) -> FxHashMap<String, String> {
+    pub fn check_extra_env(
+        &self,
+        source_root: Option<SourceRootId>,
+    ) -> FxHashMap<String, Option<String>> {
         let mut extra_env = self.cargo_extraEnv(source_root).clone();
         extra_env.extend(self.check_extraEnv(source_root).clone());
         extra_env

crates/rust-analyzer/src/discover.rs

@@ -3,6 +3,7 @@
 use std::{io, path::Path};
 
 use crossbeam_channel::Sender;
+use ide_db::FxHashMap;
 use paths::{AbsPathBuf, Utf8Path, Utf8PathBuf};
 use project_model::ProjectJsonData;
 use serde::{Deserialize, Serialize};
@@ -62,7 +63,8 @@ impl DiscoverCommand {
             })
             .collect();
 
-        let mut cmd = toolchain::command(command, current_dir);
+        // TODO: are we sure the extra env should be empty?
+        let mut cmd = toolchain::command(command, current_dir, &FxHashMap::default());
         cmd.args(args);
 
         Ok(DiscoverHandle {

crates/rust-analyzer/src/flycheck.rs

@@ -35,7 +35,7 @@ pub(crate) struct CargoOptions {
     pub(crate) features: Vec<String>,
     pub(crate) extra_args: Vec<String>,
     pub(crate) extra_test_bin_args: Vec<String>,
-    pub(crate) extra_env: FxHashMap<String, String>,
+    pub(crate) extra_env: FxHashMap<String, Option<String>>,
     pub(crate) target_dir: Option<Utf8PathBuf>,
 }
 
@@ -69,7 +69,6 @@ impl CargoOptions {
         if let Some(target_dir) = &self.target_dir {
             cmd.arg("--target-dir").arg(target_dir);
         }
-        cmd.envs(&self.extra_env);
     }
 }
 
@@ -83,7 +82,7 @@ pub(crate) enum FlycheckConfig {
     CustomCommand {
         command: String,
         args: Vec<String>,
-        extra_env: FxHashMap<String, String>,
+        extra_env: FxHashMap<String, Option<String>>,
         invocation_strategy: InvocationStrategy,
     },
 }
@@ -468,7 +467,8 @@ impl FlycheckActor {
     ) -> Option<Command> {
         match &self.config {
             FlycheckConfig::CargoCommand { command, options, ansi_color_output } => {
-                let mut cmd = toolchain::command(Tool::Cargo.path(), &*self.root);
+                let mut cmd =
+                    toolchain::command(Tool::Cargo.path(), &*self.root, &options.extra_env);
                 if let Some(sysroot_root) = &self.sysroot_root {
                     cmd.env("RUSTUP_TOOLCHAIN", AsRef::<std::path::Path>::as_ref(sysroot_root));
                 }
@@ -516,8 +516,7 @@ impl FlycheckActor {
                         &*self.root
                     }
                 };
-                let mut cmd = toolchain::command(command, root);
-                cmd.envs(extra_env);
+                let mut cmd = toolchain::command(command, root, extra_env);
 
                 // If the custom command has a $saved_file placeholder, and
                 // we're saving a file, replace the placeholder in the arguments.

crates/rust-analyzer/src/handlers/request.rs

@@ -2315,8 +2315,11 @@ fn run_rustfmt(
     let mut command = match snap.config.rustfmt(source_root_id) {
         RustfmtConfig::Rustfmt { extra_args, enable_range_formatting } => {
             // FIXME: Set RUSTUP_TOOLCHAIN
-            let mut cmd = toolchain::command(toolchain::Tool::Rustfmt.path(), current_dir);
-            cmd.envs(snap.config.extra_env(source_root_id));
+            let mut cmd = toolchain::command(
+                toolchain::Tool::Rustfmt.path(),
+                current_dir,
+                snap.config.extra_env(source_root_id),
+            );
             cmd.args(extra_args);
 
             if let Some(edition) = edition {
@@ -2358,6 +2361,7 @@ fn run_rustfmt(
         RustfmtConfig::CustomCommand { command, args } => {
             let cmd = Utf8PathBuf::from(&command);
             let target_spec = TargetSpec::for_file(snap, file_id)?;
+            let extra_env = snap.config.extra_env(source_root_id);
             let mut cmd = match target_spec {
                 Some(TargetSpec::Cargo(_)) => {
                     // approach: if the command name contains a path separator, join it with the project root.
@@ -2370,12 +2374,11 @@ fn run_rustfmt(
                     } else {
                         cmd
                     };
-                    toolchain::command(cmd_path, current_dir)
+                    toolchain::command(cmd_path, current_dir, extra_env)
                 }
-                _ => toolchain::command(cmd, current_dir),
+                _ => toolchain::command(cmd, current_dir, extra_env),
             };
 
-            cmd.envs(snap.config.extra_env(source_root_id));
             cmd.args(args);
             cmd
         }

crates/rust-analyzer/src/reload.rs

@@ -652,12 +652,14 @@ impl GlobalState {
                     | ProjectWorkspaceKind::DetachedFile { cargo: Some((cargo, ..)), .. } => cargo
                         .env()
                         .into_iter()
-                        .chain(self.config.extra_env(None))
-                        .map(|(a, b)| (a.clone(), b.clone()))
+                        .map(|(k, v)| (k.clone(), Some(v.clone())))
+                        .chain(
+                            self.config.extra_env(None).iter().map(|(k, v)| (k.clone(), v.clone())),
+                        )
                         .chain(
                             ws.sysroot
                                 .root()
-                                .map(|it| ("RUSTUP_TOOLCHAIN".to_owned(), it.to_string())),
+                                .map(|it| ("RUSTUP_TOOLCHAIN".to_owned(), Some(it.to_string()))),
                         )
                         .collect(),
 
@@ -893,7 +895,7 @@ impl GlobalState {
 // FIXME: Move this into load-cargo?
 pub fn ws_to_crate_graph(
     workspaces: &[ProjectWorkspace],
-    extra_env: &FxHashMap<String, String>,
+    extra_env: &FxHashMap<String, Option<String>>,
     mut load: impl FnMut(&AbsPath) -> Option<vfs::FileId>,
 ) -> (CrateGraphBuilder, Vec<ProcMacroPaths>) {
     let mut crate_graph = CrateGraphBuilder::default();

crates/rust-analyzer/src/test_runner.rs

@@ -101,7 +101,7 @@ impl CargoTestHandle {
         test_target: TestTarget,
         sender: Sender<CargoTestMessage>,
     ) -> std::io::Result<Self> {
-        let mut cmd = toolchain::command(Tool::Cargo.path(), root);
+        let mut cmd = toolchain::command(Tool::Cargo.path(), root, &options.extra_env);
         cmd.env("RUSTC_BOOTSTRAP", "1");
         cmd.arg("test");