diff options
| -rw-r--r-- | guix/derivations.scm | 20 |
1 files changed, 13 insertions, 7 deletions
diff --git a/guix/derivations.scm b/guix/derivations.scm index 4b0048b54b..9b5ee367b6 100644 --- a/guix/derivations.scm +++ b/guix/derivations.scm @@ -225,22 +225,28 @@ download with a fixed hash (aka. `fetchurl')." (define* (substitution-oracle store drv) "Return a one-argument procedure that, when passed a store file name, returns #t if it's substitutable and #f otherwise. The returned procedure -knows about all substitutes for all the derivations listed in DRV and their -prerequisites. +knows about all substitutes for all the derivations listed in DRV; it also +knows about their prerequisites, unless they are themselves substitutable. Creating a single oracle (thus making a single 'substitutable-paths' call) and reusing it is much more efficient than calling 'has-substitutes?' or similar repeatedly, because it avoids the costs associated with launching the substituter many times." + (define valid? + (cut valid-path? store <>)) + (let* ((paths (delete-duplicates (fold (lambda (drv result) (let ((self (match (derivation->output-paths drv) (((names . paths) ...) - paths))) - (deps (append-map derivation-input-output-paths - (derivation-prerequisites - drv)))) - (append self deps result))) + paths)))) + (if (every valid? self) + result + (let ((deps + (append-map derivation-input-output-paths + (derivation-prerequisites drv)))) + (append (remove valid? (append self deps)) + result))))) '() drv))) (subst (list->set (substitutable-paths store paths)))) |