1 files changed, 50 insertions, 0 deletions
diff --git a/guix-build-coordinator/utils.scm b/guix-build-coordinator/utils.scm
index ef26d3a..7b38130 100644
--- a/guix-build-coordinator/utils.scm
+++ b/guix-build-coordinator/utils.scm
@@ -36,6 +36,7 @@
             call-with-streaming-http-request
             make-chunked-input-port*
 
+            find-missing-substitutes-for-output
             has-substiutes-no-cache?
 
             substitute-derivation
@@ -256,6 +257,55 @@ upcoming chunk."
               (values response
                       body))))))))
 
+(define (find-missing-substitutes-for-output substitute-urls output)
+  (define %narinfo-cache-directory
+    (if (zero? (getuid))
+        (or (and=> (getenv "XDG_CACHE_HOME")
+                   (cut string-append <> "/guix/substitute"))
+            (string-append %state-directory "/substitute/cache"))
+        (string-append (cache-directory #:ensure? #f) "/substitute")))
+
+  ;; Because there's no control over the caching of 404 lookups, and I'd
+  ;; rather not reach inside and monkey patch the Guix code, just delete any
+  ;; cache files
+  (let ((hash-part (store-path-hash-part output))
+        (directories
+         (scandir %narinfo-cache-directory
+                  (lambda (s) (= (string-length s) 52)))))
+
+    (for-each (lambda (directory)
+                (let ((cache-file
+                       (string-append
+                        %narinfo-cache-directory "/"
+                        directory "/" hash-part)))
+                  (when (file-exists? cache-file)
+                    (with-exception-handler
+                        (lambda (exn)
+                          (simple-format
+                           (current-error-port)
+                           "error: when deleting substitute cache file: ~A\n"
+                           exn))
+                      (lambda ()
+                        (delete-file cache-file))
+                      #:unwind? #t))))
+              (or directories '())))
+
+  (let ((narinfo
+         (any (lambda (substitute-url)
+                (let ((result (lookup-narinfos substitute-url (list output))))
+                  (if (null? result)
+                      #f
+                      (first result))))
+              substitute-urls)))
+    (if narinfo
+        (append-map
+         (lambda (referenced-output)
+           (peek "REF" referenced-output)
+           (find-missing-substitutes-for-output substitute-urls
+                                                referenced-output))
+         (narinfo-references narinfo))
+        (list output))))
+
 (define (has-substiutes-no-cache? substitute-urls file)
   (define %narinfo-cache-directory
     (if (zero? (getuid))