11use crate :: Task ;
22use linkme:: distributed_slice;
3+ use std:: sync:: OnceLock ;
34
45/// Compat encapsulate functions to find async runtimes to spawn task.
56pub enum Compat {
7+ /// Named global function to spawn task.
8+ NamedGlobal { name : & ' static str , spawn : fn ( Task ) } ,
69 /// Global function to spawn task.
7- ///
8- /// [spawn](`crate::spawn()`) will panic if there is no local spawners but multiple global spawners.
10+ # [ doc ( hidden ) ]
11+ # [ deprecated ( since = "1.0.3" , note = "use NamedGlobal instead" ) ]
912 Global ( fn ( Task ) ) ,
1013 #[ allow( clippy:: type_complexity) ]
1114 /// Local function to detect async runtimes.
@@ -16,33 +19,85 @@ pub enum Compat {
1619#[ distributed_slice]
1720pub static COMPATS : [ Compat ] = [ ..] ;
1821
19- pub ( crate ) fn find_spawn ( ) -> Option < fn ( Task ) > {
20- match COMPATS . len ( ) {
21- 0 => return None ,
22- 1 => match COMPATS [ 0 ] {
23- Compat :: Global ( inject) => return Some ( inject) ,
24- Compat :: Local ( detect) => return detect ( ) ,
25- } ,
26- _ => { }
27- }
22+ #[ derive( Clone , Copy ) ]
23+ pub ( crate ) enum Failure {
24+ NotFound ,
25+ #[ allow( dead_code) ]
26+ MultipleGlobals ,
27+ }
2828
29- let mut last_global = None ;
29+ fn pick_global ( choose : Option < & str > ) -> Result < fn ( Task ) , Failure > {
3030 let mut globals = 0 ;
31- match COMPATS . iter ( ) . find_map ( |injection| match injection {
32- Compat :: Local ( local) => local ( ) ,
31+ let mut last_named = None ;
32+ let mut last_unnamed = None ;
33+ match COMPATS . iter ( ) . find_map ( |compat| match compat {
34+ Compat :: Local ( _) => None ,
35+ #[ allow( deprecated) ]
3336 Compat :: Global ( global) => {
3437 globals += 1 ;
35- last_global = Some ( global) ;
38+ last_unnamed = Some ( global) ;
3639 None
3740 }
41+ Compat :: NamedGlobal { spawn, name } => {
42+ if choose == Some ( name) {
43+ Some ( spawn)
44+ } else {
45+ globals += 1 ;
46+ last_named = Some ( spawn) ;
47+ None
48+ }
49+ }
3850 } ) {
39- Some ( spawn) => Some ( spawn) ,
51+ Some ( spawn) => Ok ( * spawn) ,
4052 None => {
4153 #[ cfg( feature = "panic-multiple-global-spawners" ) ]
4254 if globals > 1 {
43- panic ! ( "multiple global spawners" )
55+ return Err ( Failure :: MultipleGlobals ) ;
4456 }
45- last_global. copied ( )
57+ last_named
58+ . or ( last_unnamed)
59+ . ok_or ( Failure :: NotFound )
60+ . copied ( )
4661 }
4762 }
4863}
64+
65+ fn find_global ( ) -> Result < fn ( Task ) , Failure > {
66+ static FOUND : OnceLock < Result < fn ( Task ) , Failure > > = OnceLock :: new ( ) ;
67+ if let Some ( found) = FOUND . get ( ) {
68+ return * found;
69+ }
70+ let choose = std:: env:: var ( "SPAWNS_GLOBAL_SPAWNER" ) . ok ( ) ;
71+ let result = pick_global ( choose. as_deref ( ) ) ;
72+ * FOUND . get_or_init ( || result)
73+ }
74+
75+ fn find_local ( ) -> Option < fn ( Task ) > {
76+ COMPATS . iter ( ) . find_map ( |compat| match compat {
77+ Compat :: Local ( local) => local ( ) ,
78+ #[ allow( deprecated) ]
79+ Compat :: Global ( _) => None ,
80+ Compat :: NamedGlobal { .. } => None ,
81+ } )
82+ }
83+
84+ pub ( crate ) fn find_spawn ( ) -> Option < fn ( Task ) > {
85+ match COMPATS . len ( ) {
86+ 0 => return None ,
87+ 1 => match COMPATS [ 0 ] {
88+ Compat :: NamedGlobal { spawn, .. } => return Some ( spawn) ,
89+ #[ allow( deprecated) ]
90+ Compat :: Global ( spawn) => return Some ( spawn) ,
91+ Compat :: Local ( local) => return local ( ) ,
92+ } ,
93+ _ => { }
94+ }
95+ match find_local ( )
96+ . ok_or ( Failure :: NotFound )
97+ . or_else ( |_| find_global ( ) )
98+ {
99+ Ok ( spawn) => Some ( spawn) ,
100+ Err ( Failure :: NotFound ) => None ,
101+ Err ( Failure :: MultipleGlobals ) => panic ! ( "multiple global spawners" ) ,
102+ }
103+ }
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