Add support for custom flycheck commands with JSON project workspaces

Enable flychecks with JSON project workspaces if an override command was provided as part
of the client configuration.

crates/project_model/src/project_json.rs

@@ -13,6 +13,7 @@ use crate::cfg_flag::CfgFlag;
 #[derive(Clone, Debug, Eq, PartialEq)]
 pub struct ProjectJson {
     pub(crate) sysroot_src: Option<AbsPathBuf>,
+    project_root: Option<AbsPathBuf>,
     crates: Vec<Crate>,
 }
 
@@ -36,6 +37,7 @@ impl ProjectJson {
     pub fn new(base: &AbsPath, data: ProjectJsonData) -> ProjectJson {
         ProjectJson {
             sysroot_src: data.sysroot_src.map(|it| base.join(it)),
+            project_root: base.parent().map(AbsPath::to_path_buf),
             crates: data
                 .crates
                 .into_iter()
@@ -89,6 +91,12 @@ impl ProjectJson {
     pub fn crates(&self) -> impl Iterator<Item = (CrateId, &Crate)> + '_ {
         self.crates.iter().enumerate().map(|(idx, krate)| (CrateId(idx as u32), krate))
     }
+    pub fn path(&self) -> Option<&AbsPath> {
+        match &self.project_root {
+            Some(p) => Some(p.as_path()),
+            None => None,
+        }
+    }
 }
 
 #[derive(Deserialize)]

crates/rust-analyzer/src/reload.rs

@@ -2,7 +2,7 @@
 use std::{mem, sync::Arc};
 
 use base_db::{CrateGraph, SourceRoot, VfsPath};
-use flycheck::FlycheckHandle;
+use flycheck::{FlycheckConfig, FlycheckHandle};
 use ide::AnalysisChange;
 use project_model::{ProcMacroClient, ProjectWorkspace};
 use vfs::{file_set::FileSetConfig, AbsPath, AbsPathBuf, ChangeKind};
@@ -244,13 +244,17 @@ impl GlobalState {
             .iter()
             // FIXME: Figure out the multi-workspace situation
             .find_map(|w| match w {
-                ProjectWorkspace::Cargo { cargo, sysroot: _ } => Some(cargo),
-                ProjectWorkspace::Json { .. } => None,
-            })
-            .map(move |cargo| {
-                let cargo_project_root = cargo.workspace_root().to_path_buf();
-                FlycheckHandle::spawn(sender, config, cargo_project_root.into())
+                ProjectWorkspace::Cargo { cargo, sysroot: _ } => Some(cargo.workspace_root()),
+                ProjectWorkspace::Json { project, .. } => {
+                    // Enable flychecks for json projects if a custom flycheck command was supplied
+                    // in the workspace configuration.
+                    match config {
+                        FlycheckConfig::CustomCommand { .. } => project.path(),
+                        _ => None,
+                    }
+                }
             })
+            .map(move |root| FlycheckHandle::spawn(sender, config, root.to_path_buf().into()))
     }
 }