Rust Cargo linter: Improve workspace support (#1679)

* Rust Cargo linter: Improve workspace support

When using Cargo workspaces [1], there is a 'Cargo.toml' directory in a
top level directory, listing all the crates in the project. If we are
currently editing one of the crates, 'cargo build' should execute in
that directory for that crate's separate `Cargo.toml`, otherwise Cargo
may spend more time possibly rebuilding the entire workspace, and maybe
failing on one of the other crates, instead of succeeding on the current.

[1] https://doc.rust-lang.org/book/second-edition/ch14-03-cargo-workspaces.html

1 files changed, 14 insertions, 1 deletions

diff --git a/ale_linters/rust/cargo.vim b/ale_linters/rust/cargo.vim
index ef0c3bd1..e6c3870a 100644
--- a/ale_linters/rust/cargo.vim
+++ b/ale_linters/rust/cargo.vim
@@ -6,6 +6,7 @@ call ale#Set('rust_cargo_use_check', 1)
 call ale#Set('rust_cargo_check_all_targets', 0)
 call ale#Set('rust_cargo_check_examples', 0)
 call ale#Set('rust_cargo_check_tests', 0)
+call ale#Set('rust_cargo_avoid_whole_workspace', 1)
 call ale#Set('rust_cargo_default_feature_behavior', 'default')
 call ale#Set('rust_cargo_include_features', '')
 
@@ -45,6 +46,18 @@ function! ale_linters#rust#cargo#GetCommand(buffer, version_output) abort
         let l:include_features = ' --features ' . ale#Escape(l:include_features)
     endif
 
+    let l:avoid_whole_workspace = ale#Var(a:buffer, 'rust_cargo_avoid_whole_workspace')
+    let l:nearest_cargo_prefix = ''
+
+    if l:avoid_whole_workspace
+        let l:nearest_cargo = ale#path#FindNearestFile(a:buffer, 'Cargo.toml')
+        let l:nearest_cargo_dir = fnamemodify(l:nearest_cargo, ':h')
+
+        if l:nearest_cargo_dir isnot# '.'
+            let l:nearest_cargo_prefix = 'cd '. ale#Escape(l:nearest_cargo_dir) .' && '
+        endif
+    endif
+
     let l:default_feature_behavior = ale#Var(a:buffer, 'rust_cargo_default_feature_behavior')
     if l:default_feature_behavior is# 'all'
         let l:include_features = ''
@@ -55,7 +68,7 @@ function! ale_linters#rust#cargo#GetCommand(buffer, version_output) abort
         let l:default_feature = ''
     endif
 
-    return 'cargo '
+    return l:nearest_cargo_prefix . 'cargo '
     \   . (l:use_check ? 'check' : 'build')
     \   . (l:use_all_targets ? ' --all-targets' : '')
     \   . (l:use_examples ? ' --examples' : '')