guix: substitutes: Make progress reporting configurable.

Rather than always outputting to (current-error-port) in
lookup-narinfos (which is called from within lookup-narinfos/diverse), take a
procedure which should return a progress reporter, and defer any output to
that.

As this is now general purpose code, make the default behaviour to output
nothing. Maintain the current behaviour of the substitute script by moving the
progress reporter implementation there, and passing it in when calling
lookup-narinfos/diverse.

These changes should be generally useful, but I'm particularly looking at
getting guix weather to do progress reporting differently, with this new
flexibility.

* guix/substitutes.scm (fetch-narinfos): Take a procedure to make a
progress-reporter, and use that rather than the hardcoded behaviour.
(lookup-narinfos): Add #:make-progress-reporter keyword argument, and pass
this through to fetch-narinfos.
(lookup-narinfos/diverse): Add a #:make-progress-reporter keyword argument,
and pass this through to lookup-narinfos.
* guix/scripts/substitute.scm (process-query): Pass a progress-reporter to
lookup-narinfos/diverse.

2 files changed, 43 insertions, 20 deletions

diff --git a/guix/scripts/substitute.scm b/guix/scripts/substitute.scm
index 5866b8bb0a..6892aa999b 100755
--- a/guix/scripts/substitute.scm
+++ b/guix/scripts/substitute.scm
@@ -288,12 +288,30 @@ authorized substitutes."
         (lambda (obj)
           (valid-narinfo? obj acl))))
 
+  (define* (make-progress-reporter total #:key url)
+    (define done 0)
+
+    (define (report-progress)
+      (erase-current-line (current-error-port)) ;erase current line
+      (force-output (current-error-port))
+      (format (current-error-port)
+              (G_ "updating substitutes from '~a'... ~5,1f%")
+              url (* 100. (/ done total)))
+      (set! done (+ 1 done)))
+
+    (progress-reporter
+     (start report-progress)
+     (report report-progress)
+     (stop (lambda ()
+             (newline (current-error-port))))))
+
   (match (string-tokenize command)
     (("have" paths ..1)
      ;; Return the subset of PATHS available in CACHE-URLS.
      (let ((substitutable (lookup-narinfos/diverse
                            cache-urls paths valid?
-                           #:open-connection open-connection-for-uri/cached)))
+                           #:open-connection open-connection-for-uri/cached
+                           #:make-progress-reporter make-progress-reporter)))
        (for-each (lambda (narinfo)
                    (format #t "~a~%" (narinfo-path narinfo)))
                  substitutable)
@@ -302,7 +320,8 @@ authorized substitutes."
      ;; Reply info about PATHS if it's in CACHE-URLS.
      (let ((substitutable (lookup-narinfos/diverse
                            cache-urls paths valid?
-                           #:open-connection open-connection-for-uri/cached)))
+                           #:open-connection open-connection-for-uri/cached
+                           #:make-progress-reporter make-progress-reporter)))
        (for-each display-narinfo-data substitutable)
        (newline)))
     (wtf
diff --git a/guix/substitutes.scm b/guix/substitutes.scm
index dc94ccc8e4..ef78013659 100644
--- a/guix/substitutes.scm
+++ b/guix/substitutes.scm
@@ -173,18 +173,14 @@ if file doesn't exist, and the narinfo otherwise."
           (apply throw args)))))
 
 (define* (fetch-narinfos url paths
-                         #:key (open-connection guix:open-connection-for-uri))
+                         #:key
+                         (open-connection guix:open-connection-for-uri)
+                         (make-progress-reporter
+                          (const progress-reporter/silent)))
   "Retrieve all the narinfos for PATHS from the cache at URL and return them."
-  (define update-progress!
-    (let ((done 0)
-          (total (length paths)))
-      (lambda ()
-        (display "\r\x1b[K" (current-error-port)) ;erase current line
-        (force-output (current-error-port))
-        (format (current-error-port)
-                (G_ "updating substitutes from '~a'... ~5,1f%")
-                url (* 100. (/ done total)))
-        (set! done (+ 1 done)))))
+  (define progress-reporter
+    (make-progress-reporter (length paths)
+                            #:url url))
 
   (define hash-part->path
     (let ((mapping (fold (lambda (path result)
@@ -206,7 +202,7 @@ if file doesn't exist, and the narinfo otherwise."
            (len    (response-content-length response))
            (cache  (response-cache-control response))
            (ttl    (and cache (assoc-ref cache 'max-age))))
-      (update-progress!)
+      (progress-reporter-report! progress-reporter)
 
       ;; Make sure to read no more than LEN bytes since subsequent bytes may
       ;; belong to the next response.
@@ -238,7 +234,7 @@ if file doesn't exist, and the narinfo otherwise."
        ;; narinfos, which provides a much stronger guarantee.
        (let* ((requests (map (cut narinfo-request url <>) paths))
               (result   (begin
-                          (update-progress!)
+                          (start-progress-reporter! progress-reporter)
                           (call-with-connection-error-handling
                            uri
                            (lambda ()
@@ -247,7 +243,7 @@ if file doesn't exist, and the narinfo otherwise."
                                                 requests
                                                 #:open-connection open-connection
                                                 #:verify-certificate? #f))))))
-         (newline (current-error-port))
+         (stop-progress-reporter! progress-reporter)
          result))
       ((file #f)
        (let* ((base  (string-append (uri-path uri) "/"))
@@ -297,7 +293,9 @@ for PATH."
       (values #f #f))))
 
 (define* (lookup-narinfos cache paths
-                          #:key (open-connection guix:open-connection-for-uri))
+                          #:key (open-connection guix:open-connection-for-uri)
+                          (make-progress-reporter
+                           (const progress-reporter/silent)))
   "Return the narinfos for PATHS, invoking the server at CACHE when no
 information is available locally."
   (let-values (((cached missing)
@@ -315,12 +313,16 @@ information is available locally."
     (if (null? missing)
         cached
         (let ((missing (fetch-narinfos cache missing
-                                       #:open-connection open-connection)))
+                                       #:open-connection open-connection
+                                       #:make-progress-reporter
+                                       make-progress-reporter)))
           (append cached (or missing '()))))))
 
 (define* (lookup-narinfos/diverse caches paths authorized?
                                   #:key (open-connection
-                                         guix:open-connection-for-uri))
+                                         guix:open-connection-for-uri)
+                                  (make-progress-reporter
+                                   (const progress-reporter/silent)))
   "Look up narinfos for PATHS on all of CACHES, a list of URLS, in that order.
 That is, when a cache lacks an AUTHORIZED? narinfo, look it up in the next
 cache, and so on.
@@ -353,7 +355,9 @@ AUTHORIZED? narinfo."
        (match caches
          ((cache rest ...)
           (let* ((narinfos (lookup-narinfos cache paths
-                                            #:open-connection open-connection))
+                                            #:open-connection open-connection
+                                            #:make-progress-reporter
+                                            make-progress-reporter))
                  (definite (map narinfo-path (filter authorized? narinfos)))
                  (missing  (lset-difference string=? paths definite))) ;XXX: perf
             (loop rest missing