Implement a config override for the default #[cfg(test)] in cargo crates

Fixes crates which vanish when the 'test' cfg atom is set.

Fix rust-lang#7243.
Fix rust-lang#9203.
Fix rust-lang#7225.

crates/cfg/src/lib.rs

@@ -52,6 +52,7 @@ impl CfgOptions {
     }
 }
 
+#[derive(Clone, Debug, PartialEq, Eq)]
 pub struct CfgDiff {
     // Invariants: No duplicates, no atom that's both in `enable` and `disable`.
     enable: Vec<CfgAtom>,

crates/project_model/src/cargo_workspace.rs

@@ -1,5 +1,6 @@
 //! See [`CargoWorkspace`].
 
+use std::iter;
 use std::path::PathBuf;
 use std::{convert::TryInto, ops, process::Command, sync::Arc};
 
@@ -12,6 +13,7 @@ use rustc_hash::FxHashMap;
 use serde::Deserialize;
 use serde_json::from_value;
 
+use crate::CfgOverrides;
 use crate::{build_data::BuildDataConfig, utf8_stdout};
 
 /// [`CargoWorkspace`] represents the logical structure of, well, a Cargo
@@ -76,6 +78,21 @@ pub struct CargoConfig {
 
     /// rustc private crate source
     pub rustc_source: Option<RustcSource>,
+
+    /// crates to disable `#[cfg(test)]` on
+    pub unset_test_crates: Vec<String>,
+}
+
+impl CargoConfig {
+    pub fn cfg_overrides(&self) -> CfgOverrides {
+        self.unset_test_crates
+            .iter()
+            .cloned()
+            .zip(iter::repeat_with(|| {
+                cfg::CfgDiff::new(Vec::new(), vec![cfg::CfgAtom::Flag("test".into())]).unwrap()
+            }))
+            .collect()
+    }
 }
 
 pub type Package = Idx<PackageData>;

crates/project_model/src/lib.rs

@@ -41,7 +41,7 @@ pub use crate::{
     },
     project_json::{ProjectJson, ProjectJsonData},
     sysroot::Sysroot,
-    workspace::{PackageRoot, ProjectWorkspace},
+    workspace::{CfgOverrides, PackageRoot, ProjectWorkspace},
 };
 
 pub use proc_macro_api::ProcMacroClient;

crates/project_model/src/workspace.rs

@@ -7,7 +7,7 @@ use std::{collections::VecDeque, fmt, fs, path::Path, process::Command};
 use anyhow::{format_err, Context, Result};
 use base_db::{CrateDisplayName, CrateGraph, CrateId, CrateName, Edition, Env, FileId, ProcMacro};
 use cargo_workspace::DepKind;
-use cfg::{CfgAtom, CfgDiff, CfgOptions};
+use cfg::{CfgDiff, CfgOptions};
 use paths::{AbsPath, AbsPathBuf};
 use proc_macro_api::ProcMacroClient;
 use rustc_hash::{FxHashMap, FxHashSet};
@@ -22,6 +22,8 @@ use crate::{
     Sysroot, TargetKind,
 };
 
+pub type CfgOverrides = FxHashMap<String, CfgDiff>;
+
 /// `PackageRoot` describes a package root folder.
 /// Which may be an external dependency, or a member of
 /// the current workspace.
@@ -46,6 +48,7 @@ pub enum ProjectWorkspace {
         /// FIXME: make this a per-crate map, as, eg, build.rs might have a
         /// different target.
         rustc_cfg: Vec<CfgFlag>,
+        cfg_overrides: CfgOverrides,
     },
     /// Project workspace was manually specified using a `rust-project.json` file.
     Json { project: ProjectJson, sysroot: Option<Sysroot>, rustc_cfg: Vec<CfgFlag> },
@@ -67,7 +70,7 @@ impl fmt::Debug for ProjectWorkspace {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         // Make sure this isn't too verbose.
         match self {
-            ProjectWorkspace::Cargo { cargo, sysroot, rustc, rustc_cfg } => f
+            ProjectWorkspace::Cargo { cargo, sysroot, rustc, rustc_cfg, cfg_overrides } => f
                 .debug_struct("Cargo")
                 .field("root", &cargo.workspace_root().file_name())
                 .field("n_packages", &cargo.packages().len())
@@ -77,6 +80,7 @@ impl fmt::Debug for ProjectWorkspace {
                     &rustc.as_ref().map_or(0, |rc| rc.packages().len()),
                 )
                 .field("n_rustc_cfg", &rustc_cfg.len())
+                .field("n_cfg_overrides", &cfg_overrides.len())
                 .finish(),
             ProjectWorkspace::Json { project, sysroot, rustc_cfg } => {
                 let mut debug_struct = f.debug_struct("Json");
@@ -164,7 +168,9 @@ impl ProjectWorkspace {
                 };
 
                 let rustc_cfg = rustc_cfg::get(Some(&cargo_toml), config.target.as_deref());
-                ProjectWorkspace::Cargo { cargo, sysroot, rustc, rustc_cfg }
+
+                let cfg_overrides = config.cfg_overrides();
+                ProjectWorkspace::Cargo { cargo, sysroot, rustc, rustc_cfg, cfg_overrides }
             }
         };
 
@@ -213,43 +219,45 @@ impl ProjectWorkspace {
                     })
                 }))
                 .collect::<Vec<_>>(),
-            ProjectWorkspace::Cargo { cargo, sysroot, rustc, rustc_cfg: _ } => cargo
-                .packages()
-                .map(|pkg| {
-                    let is_member = cargo[pkg].is_member;
-                    let pkg_root = cargo[pkg].root().to_path_buf();
-
-                    let mut include = vec![pkg_root.clone()];
-                    include.extend(
-                        build_data
-                            .and_then(|it| it.get(cargo.workspace_root()))
-                            .and_then(|map| map.get(&cargo[pkg].id))
-                            .and_then(|it| it.out_dir.clone()),
-                    );
+            ProjectWorkspace::Cargo { cargo, sysroot, rustc, rustc_cfg: _, cfg_overrides: _ } => {
+                cargo
+                    .packages()
+                    .map(|pkg| {
+                        let is_member = cargo[pkg].is_member;
+                        let pkg_root = cargo[pkg].root().to_path_buf();
+
+                        let mut include = vec![pkg_root.clone()];
+                        include.extend(
+                            build_data
+                                .and_then(|it| it.get(cargo.workspace_root()))
+                                .and_then(|map| map.get(&cargo[pkg].id))
+                                .and_then(|it| it.out_dir.clone()),
+                        );
 
-                    let mut exclude = vec![pkg_root.join(".git")];
-                    if is_member {
-                        exclude.push(pkg_root.join("target"));
-                    } else {
-                        exclude.push(pkg_root.join("tests"));
-                        exclude.push(pkg_root.join("examples"));
-                        exclude.push(pkg_root.join("benches"));
-                    }
-                    PackageRoot { is_member, include, exclude }
-                })
-                .chain(sysroot.crates().map(|krate| PackageRoot {
-                    is_member: false,
-                    include: vec![sysroot[krate].root_dir().to_path_buf()],
-                    exclude: Vec::new(),
-                }))
-                .chain(rustc.into_iter().flat_map(|rustc| {
-                    rustc.packages().map(move |krate| PackageRoot {
+                        let mut exclude = vec![pkg_root.join(".git")];
+                        if is_member {
+                            exclude.push(pkg_root.join("target"));
+                        } else {
+                            exclude.push(pkg_root.join("tests"));
+                            exclude.push(pkg_root.join("examples"));
+                            exclude.push(pkg_root.join("benches"));
+                        }
+                        PackageRoot { is_member, include, exclude }
+                    })
+                    .chain(sysroot.crates().map(|krate| PackageRoot {
                         is_member: false,
-                        include: vec![rustc[krate].root().to_path_buf()],
+                        include: vec![sysroot[krate].root_dir().to_path_buf()],
                         exclude: Vec::new(),
-                    })
-                }))
-                .collect(),
+                    }))
+                    .chain(rustc.into_iter().flat_map(|rustc| {
+                        rustc.packages().map(move |krate| PackageRoot {
+                            is_member: false,
+                            include: vec![rustc[krate].root().to_path_buf()],
+                            exclude: Vec::new(),
+                        })
+                    }))
+                    .collect()
+            }
             ProjectWorkspace::DetachedFiles { files, sysroot, .. } => files
                 .into_iter()
                 .map(|detached_file| PackageRoot {
@@ -299,16 +307,22 @@ impl ProjectWorkspace {
                 project,
                 sysroot,
             ),
-            ProjectWorkspace::Cargo { cargo, sysroot, rustc, rustc_cfg } => cargo_to_crate_graph(
-                rustc_cfg.clone(),
-                &proc_macro_loader,
-                load,
-                cargo,
-                build_data.and_then(|it| it.get(cargo.workspace_root())),
-                sysroot,
-                rustc,
-                rustc.as_ref().zip(build_data).and_then(|(it, map)| map.get(it.workspace_root())),
-            ),
+            ProjectWorkspace::Cargo { cargo, sysroot, rustc, rustc_cfg, cfg_overrides } => {
+                cargo_to_crate_graph(
+                    rustc_cfg.clone(),
+                    cfg_overrides,
+                    &proc_macro_loader,
+                    load,
+                    cargo,
+                    build_data.and_then(|it| it.get(cargo.workspace_root())),
+                    sysroot,
+                    rustc,
+                    rustc
+                        .as_ref()
+                        .zip(build_data)
+                        .and_then(|(it, map)| map.get(it.workspace_root())),
+                )
+            }
             ProjectWorkspace::DetachedFiles { files, sysroot, rustc_cfg } => {
                 detached_files_to_crate_graph(rustc_cfg.clone(), load, files, sysroot)
             }
@@ -398,6 +412,7 @@ fn project_json_to_crate_graph(
 
 fn cargo_to_crate_graph(
     rustc_cfg: Vec<CfgFlag>,
+    override_cfg: &CfgOverrides,
     proc_macro_loader: &dyn Fn(&Path) -> Vec<ProcMacro>,
     load: &mut dyn FnMut(&AbsPath) -> Option<FileId>,
     cargo: &CargoWorkspace,
@@ -427,15 +442,16 @@ fn cargo_to_crate_graph(
     for pkg in cargo.packages() {
         let mut cfg_options = &cfg_options;
         let mut replaced_cfg_options;
-        if cargo[pkg].name == "core" {
-            // FIXME: in the specific case of libcore in rust-lang/rust (i.e. it is not coming from
-            // a sysroot), there's a `#![cfg(not(test))]` at the top of it that makes its contents
-            // get ignored by r-a. We should implement a more general solution for this
+        if let Some(overrides) = override_cfg.get(&cargo[pkg].name) {
+            // FIXME: this is sort of a hack to deal with #![cfg(not(test))] vanishing such as seen
+            // in ed25519_dalek (#7243), and libcore (#9203) (although you only hit that one while
+            // working on rust-lang/rust as that's the only time it appears outside sysroot).
+            //
+            // A more ideal solution might be to reanalyze crates based on where the cursor is and
+            // figure out the set of cfgs that would have to apply to make it active.
 
             replaced_cfg_options = cfg_options.clone();
-            replaced_cfg_options.apply_diff(
-                CfgDiff::new(Default::default(), vec![CfgAtom::Flag("test".into())]).unwrap(),
-            );
+            replaced_cfg_options.apply_diff(overrides.clone());
             cfg_options = &replaced_cfg_options;
         };
 

crates/rust-analyzer/src/config.rs

@@ -55,6 +55,8 @@ config_data! {
         cargo_autoreload: bool           = "true",
         /// Activate all available features (`--all-features`).
         cargo_allFeatures: bool          = "false",
+        /// Unsets `#[cfg(test)]` for the specified crates.
+        cargo_unsetTest: Vec<String>   = "[\"core\"]",
         /// List of features to activate.
         cargo_features: Vec<String>      = "[]",
         /// Run build scripts (`build.rs`) for more precise code analysis.
@@ -595,8 +597,10 @@ impl Config {
             target: self.data.cargo_target.clone(),
             rustc_source,
             no_sysroot: self.data.cargo_noSysroot,
+            unset_test_crates: self.data.cargo_unsetTest.clone(),
         }
     }
+
     pub fn rustfmt(&self) -> RustfmtConfig {
         match &self.data.rustfmt_overrideCommand {
             Some(args) if !args.is_empty() => {

docs/user/generated_config.adoc

@@ -39,6 +39,11 @@ Automatically refresh project info via `cargo metadata` on
 --
 Activate all available features (`--all-features`).
 --
+[[rust-analyzer.cargo.unsetTest]]rust-analyzer.cargo.unsetTest (default: `["core"]`)::
++
+--
+Unsets `#[cfg(test)]` for the specified crates.
+--
 [[rust-analyzer.cargo.features]]rust-analyzer.cargo.features (default: `[]`)::
 +
 --

editors/code/package.json

@@ -452,6 +452,16 @@
                     "default": false,
                     "type": "boolean"
                 },
+                "rust-analyzer.cargo.unsetTest": {
+                    "markdownDescription": "Unsets `#[cfg(test)]` for the specified crates.",
+                    "default": [
+                        "core"
+                    ],
+                    "type": "array",
+                    "items": {
+                        "type": "string"
+                    }
+                },
                 "rust-analyzer.cargo.features": {
                     "markdownDescription": "List of features to activate.",
                     "default": [],