check-cfg: only print the list of expected names once

Urgau · Urgau · commit c66d4699cfaa · 2023-10-12T17:01:55.000+02:00
diff --git a/compiler/rustc_errors/src/diagnostic_builder.rs b/compiler/rustc_errors/src/diagnostic_builder.rs
@@ -659,6 +659,7 @@ impl<'a, G: EmissionGuarantee> DiagnosticBuilder<'a, G> {
         msg: impl Into<SubdiagnosticMessage>,
     ) -> &mut Self);
     forward!(pub fn help(&mut self, msg: impl Into<SubdiagnosticMessage>) -> &mut Self);
+    forward!(pub fn help_once(&mut self, msg: impl Into<SubdiagnosticMessage>) -> &mut Self);
     forward!(pub fn span_help(
         &mut self,
         sp: impl Into<MultiSpan>,
diff --git a/compiler/rustc_lint/src/context.rs b/compiler/rustc_lint/src/context.rs
@@ -759,7 +759,11 @@ pub trait LintContext: Sized {
 
                         if !possibilities.is_empty() {
                             let possibilities = possibilities.join("`, `");
-                            db.help(format!("expected names are: `{possibilities}`"));
+                            // The list of expected names can be long (even by default) and
+                            // so the diagnostic produced can take a lot of space. To avoid
+                            // cloging the user output we only want to print that diagnostic
+                            // once.
+                            db.help_once(format!("expected names are: `{possibilities}`"));
                         }
                     }
                 },
diff --git a/tests/ui/check-cfg/mix.stderr b/tests/ui/check-cfg/mix.stderr
@@ -73,24 +73,18 @@ warning: unexpected `cfg` condition name: `xxx`
    |
 LL |     cfg!(xxx = "foo");
    |          ^^^^^^^^^^^
-   |
-   = help: expected names are: `debug_assertions`, `doc`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `sanitize`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `test`, `unix`, `windows`
 
 warning: unexpected `cfg` condition name: `xxx`
   --> $DIR/mix.rs:48:10
    |
 LL |     cfg!(xxx);
    |          ^^^
-   |
-   = help: expected names are: `debug_assertions`, `doc`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `sanitize`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `test`, `unix`, `windows`
 
 warning: unexpected `cfg` condition name: `xxx`
   --> $DIR/mix.rs:50:14
    |
 LL |     cfg!(any(xxx, windows));
    |              ^^^
-   |
-   = help: expected names are: `debug_assertions`, `doc`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `sanitize`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `test`, `unix`, `windows`
 
 warning: unexpected `cfg` condition value: `bad`
   --> $DIR/mix.rs:52:14
@@ -105,48 +99,36 @@ warning: unexpected `cfg` condition name: `xxx`
    |
 LL |     cfg!(any(windows, xxx));
    |                       ^^^
-   |
-   = help: expected names are: `debug_assertions`, `doc`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `sanitize`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `test`, `unix`, `windows`
 
 warning: unexpected `cfg` condition name: `xxx`
   --> $DIR/mix.rs:56:20
    |
 LL |     cfg!(all(unix, xxx));
    |                    ^^^
-   |
-   = help: expected names are: `debug_assertions`, `doc`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `sanitize`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `test`, `unix`, `windows`
 
 warning: unexpected `cfg` condition name: `aa`
   --> $DIR/mix.rs:58:14
    |
 LL |     cfg!(all(aa, bb));
    |              ^^
-   |
-   = help: expected names are: `debug_assertions`, `doc`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `sanitize`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `test`, `unix`, `windows`
 
 warning: unexpected `cfg` condition name: `bb`
   --> $DIR/mix.rs:58:18
    |
 LL |     cfg!(all(aa, bb));
    |                  ^^
-   |
-   = help: expected names are: `debug_assertions`, `doc`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `sanitize`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `test`, `unix`, `windows`
 
 warning: unexpected `cfg` condition name: `aa`
   --> $DIR/mix.rs:61:14
    |
 LL |     cfg!(any(aa, bb));
    |              ^^
-   |
-   = help: expected names are: `debug_assertions`, `doc`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `sanitize`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `test`, `unix`, `windows`
 
 warning: unexpected `cfg` condition name: `bb`
   --> $DIR/mix.rs:61:18
    |
 LL |     cfg!(any(aa, bb));
    |                  ^^
-   |
-   = help: expected names are: `debug_assertions`, `doc`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `sanitize`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `test`, `unix`, `windows`
 
 warning: unexpected `cfg` condition value: `zebra`
   --> $DIR/mix.rs:64:20
@@ -161,8 +143,6 @@ warning: unexpected `cfg` condition name: `xxx`
    |
 LL |     cfg!(any(xxx, feature = "zebra"));
    |              ^^^
-   |
-   = help: expected names are: `debug_assertions`, `doc`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `sanitize`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `test`, `unix`, `windows`
 
 warning: unexpected `cfg` condition value: `zebra`
   --> $DIR/mix.rs:66:19
@@ -177,16 +157,12 @@ warning: unexpected `cfg` condition name: `xxx`
    |
 LL |     cfg!(any(xxx, unix, xxx));
    |              ^^^
-   |
-   = help: expected names are: `debug_assertions`, `doc`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `sanitize`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `test`, `unix`, `windows`
 
 warning: unexpected `cfg` condition name: `xxx`
   --> $DIR/mix.rs:69:25
    |
 LL |     cfg!(any(xxx, unix, xxx));
    |                         ^^^
-   |
-   = help: expected names are: `debug_assertions`, `doc`, `doctest`, `feature`, `miri`, `overflow_checks`, `panic`, `proc_macro`, `relocation_model`, `sanitize`, `target_abi`, `target_arch`, `target_endian`, `target_env`, `target_family`, `target_feature`, `target_has_atomic`, `target_has_atomic_equal_alignment`, `target_has_atomic_load_store`, `target_os`, `target_pointer_width`, `target_thread_local`, `target_vendor`, `test`, `unix`, `windows`
 
 warning: unexpected `cfg` condition value: `zebra`
   --> $DIR/mix.rs:72:14

Original file line number	Diff line number	Diff line change
`@@ -759,7 +759,11 @@ pub trait LintContext: Sized {`
`759`	`759`
`760`	`760`	`if !possibilities.is_empty() {`
`761`	`761`	let possibilities = possibilities.join("`, `");
`762`		- db.help(format!("expected names are: `{possibilities}`"));
	`762`	`+ // The list of expected names can be long (even by default) and`
	`763`	`+ // so the diagnostic produced can take a lot of space. To avoid`
	`764`	`+ // cloging the user output we only want to print that diagnostic`
	`765`	`+ // once.`
	`766`	+ db.help_once(format!("expected names are: `{possibilities}`"));
`763`	`767`	`}`
`764`	`768`	`}`
`765`	`769`	`},`