publish: Do not publish nars for invalid store items.

Before that, /nar requests could succeed if the requested store item
exists but is invalid (although such requests were unlikely because the
corresponding narinfo request would have failed.)

* guix/scripts/publish.scm (render-nar): Add 'store' parameter.  Use
'valid-path?' instead of 'file-exists?'.
(make-request-handler): Adjust 'render-nar' call accordingly.
* tests/publish.scm ("/nar/invalid"): New test.

1 files changed, 8 insertions, 0 deletions

diff --git a/tests/publish.scm b/tests/publish.scm
index 0b92390900..6c710fe0a7 100644
--- a/tests/publish.scm
+++ b/tests/publish.scm
@@ -112,6 +112,14 @@ References: ~a~%"
        (call-with-input-string nar (cut restore-file <> temp)))
      (call-with-input-file temp read-string))))
 
+(test-equal "/nar/invalid"
+  404
+  (begin
+    (call-with-output-file (string-append (%store-prefix) "/invalid")
+      (lambda (port)
+        (display "This file is not a valid store item." port)))
+    (response-code (http-get (publish-uri (string-append "/nar/invalid"))))))
+
 (test-end "publish")