Rust checker: allow secondary spans to be ignored (#1696)

* Rust checker: allow secondary spans to be ignored
* test/handler/test_rust_handler.vader: Add tests for g:ale_rust_ignore_secondary_spans

3 files changed, 169 insertions, 0 deletions

diff --git a/autoload/ale/handlers/rust.vim b/autoload/ale/handlers/rust.vim
index f12c53be..c6a4b670 100644
--- a/autoload/ale/handlers/rust.vim
+++ b/autoload/ale/handlers/rust.vim
@@ -7,6 +7,10 @@ if !exists('g:ale_rust_ignore_error_codes')
     let g:ale_rust_ignore_error_codes = []
 endif
 
+if !exists('g:ale_rust_ignore_secondary_spans')
+    let g:ale_rust_ignore_secondary_spans = 0
+endif
+
 function! s:FindSpan(buffer, span) abort
     if ale#path#IsBufferPath(a:buffer, a:span.file_name) || a:span.file_name is# '<anon>'
         return a:span
@@ -47,6 +51,10 @@ function! ale#handlers#rust#HandleRustErrors(buffer, lines) abort
         for l:root_span in l:error.spans
             let l:span = s:FindSpan(a:buffer, l:root_span)
 
+            if ale#Var(a:buffer, 'rust_ignore_secondary_spans') && !get(l:span, 'is_primary', 1)
+                continue
+            endif
+
             if !empty(l:span)
                 call add(l:output, {
                 \   'lnum': l:span.line_start,
diff --git a/doc/ale-rust.txt b/doc/ale-rust.txt
index ce5634ae..7510dfbd 100644
--- a/doc/ale-rust.txt
+++ b/doc/ale-rust.txt
@@ -198,6 +198,22 @@ g:ale_rust_ignore_error_codes                   *g:ale_rust_ignore_error_codes*
   >
   let g:ale_rust_ignore_error_codes = ['E0432', 'E0433']
 
+g:ale_rust_ignore_secondary_spans           *g:ale_rust_ignore_secondary_spans*
+                                            *b:ale_rust_ignore_secondary_spans*
+  Type: Number
+  Default: 0
+
+	When set to 1, instructs the Rust error repporting to ignore secondary
+	spans. The problem with secondary spans is that they sometimes appear in
+	error messages before the main cause of the error, for example: >
+
+  1 src/main.rs|98 col 5 error| this function takes 4 parameters but 5
+	parameters were supplied: defined here
+  2 src/main.rs|430 col 32 error| this function takes 4 parameters but 5
+	parameters were supplied: expected 4 parameters
+<
+  This is due to the sorting by line numbers. With this option set to 1,
+  the 'defined here' span will not be presented.
 
 ===============================================================================
 rustfmt                                                      *ale-rust-rustfmt*
diff --git a/test/handler/test_rust_handler.vader b/test/handler/test_rust_handler.vader
index e3ab3e86..4764e713 100644
--- a/test/handler/test_rust_handler.vader
+++ b/test/handler/test_rust_handler.vader
@@ -285,3 +285,148 @@ Execute(The Rust handler should find correct files):
   \     },
   \   }),
   \ ])
+
+Execute(The Rust handler should remove secondary spans if set):
+  call ale#test#SetFilename('src/noerrors/mod.rs')
+
+  let g:ale_rust_ignore_secondary_spans = 0
+  AssertEqual
+  \ [
+  \   {
+  \     'lnum': 1,
+  \     'end_lnum': 1,
+  \     'type': 'E',
+  \     'end_col': 21,
+  \     'col': 1,
+  \     'text': 'this function takes 1 parameter but 0 were supplied: defined here',
+  \   },
+  \   {
+  \     'lnum': 1,
+  \     'end_lnum': 1,
+  \     'type': 'E',
+  \     'end_col': 46,
+  \     'col': 40,
+  \     'text': 'this function takes 1 parameter but 0 were supplied: expected 1 parameter',
+  \   },
+  \ ],
+  \ ale#handlers#rust#HandleRustErrors(bufnr(''), [
+  \   '',
+  \   'fn test(x: u8) -> u8 { x } fn main() { x(); }',
+  \   json_encode({
+  \     'message': {
+  \       'code': {
+  \         'code': 'E0061',
+  \         'explanation': 'Dummy explanation; not used'
+  \       },
+  \       'level': 'error',
+  \       'message': 'this function takes 1 parameter but 0 were supplied',
+  \       'spans': [
+  \         {
+  \           'byte_end': 20,
+  \           'byte_start': 0,
+  \           'column_end': 21,
+  \           'column_start': 1,
+  \           'file_name': 'src/noerrors/mod.rs',
+  \           'is_primary': v:false,
+  \           'label': 'defined here',
+  \           'line_end': 1,
+  \           'line_start': 1,
+  \         },
+  \         {
+  \           'byte_end': 45,
+  \           'byte_start': 39,
+  \           'column_end': 46,
+  \           'column_start': 40,
+  \           'file_name': '<anon>',
+  \           'is_primary': v:true,
+  \           'label': 'expected 1 parameter',
+  \           'line_end': 1,
+  \           'line_start': 1,
+  \         },
+  \       ]
+  \     },
+  \   }),
+  \   json_encode({
+  \     'message': {
+  \       'code': v:null,
+  \       'level': 'error',
+  \       'message': 'aborting due to previous error',
+  \       'spans': []
+  \     },
+  \   }),
+  \   json_encode({
+  \     'message': {
+  \       'code': v:null,
+  \       'level': 'error',
+  \       'message': 'For more information about this error, try `rustc --explain E0061`.',
+  \       'spans': []
+  \     },
+  \   }),
+  \ ])
+
+  let g:ale_rust_ignore_secondary_spans = 1
+  AssertEqual
+  \ [
+  \   {
+  \     'lnum': 1,
+  \     'end_lnum': 1,
+  \     'type': 'E',
+  \     'end_col': 46,
+  \     'col': 40,
+  \     'text': 'this function takes 1 parameter but 0 were supplied: expected 1 parameter',
+  \   },
+  \ ],
+  \ ale#handlers#rust#HandleRustErrors(bufnr(''), [
+  \   '',
+  \   'fn test(x: u8) -> u8 { x } fn main() { x(); }',
+  \   json_encode({
+  \     'message': {
+  \       'code': {
+  \         'code': 'E0061',
+  \         'explanation': 'Dummy explanation; not used'
+  \       },
+  \       'level': 'error',
+  \       'message': 'this function takes 1 parameter but 0 were supplied',
+  \       'spans': [
+  \         {
+  \           'byte_end': 20,
+  \           'byte_start': 0,
+  \           'column_end': 21,
+  \           'column_start': 1,
+  \           'file_name': 'src/noerrors/mod.rs',
+  \           'is_primary': v:false,
+  \           'label': 'defined here',
+  \           'line_end': 1,
+  \           'line_start': 1,
+  \         },
+  \         {
+  \           'byte_end': 45,
+  \           'byte_start': 39,
+  \           'column_end': 46,
+  \           'column_start': 40,
+  \           'file_name': '<anon>',
+  \           'is_primary': v:true,
+  \           'label': 'expected 1 parameter',
+  \           'line_end': 1,
+  \           'line_start': 1,
+  \         },
+  \       ]
+  \     },
+  \   }),
+  \   json_encode({
+  \     'message': {
+  \       'code': v:null,
+  \       'level': 'error',
+  \       'message': 'aborting due to previous error',
+  \       'spans': []
+  \     },
+  \   }),
+  \   json_encode({
+  \     'message': {
+  \       'code': v:null,
+  \       'level': 'error',
+  \       'message': 'For more information about this error, try `rustc --explain E0061`.',
+  \       'spans': []
+  \     },
+  \   }),
+  \ ])