Subject: [bug#50238] [PATCH] build-self: Try printing nicer error messages.

From: Maxime Devos <[email-masked]>
Date: Sat, 28 Aug 2021 16:36:48 +0200

Hi guix,

This patch improves the error message generated by "guix time-machine"
and presumably "guix pull" as well when the guix derivation fails to
compute.

Before: something like <https://issues.guix.gnu.org/50232>.
After: something like

[...]
substitute: lijst van substitutes van ?[...]? aan het bijwerken... 100.0%
/gnu/store/4yx3vms0rfpzd1430za3g4pa6jvjsfw9-nowhere.tar.bz2.drv bouwen...
/error: build of `/gnu/store/6s0cmkfa4hq7d9w8g08mv2rhq0cr7wqc-subversion-1.14.1.drv' failed
guix time-machine: fout: You found a bug: the program '/gnu/store/j07lizpjf7v65shdgxyxddz171g6vjvx-compute-guix-derivation'
failed to compute the derivation for Guix (version: "9fc551e089c25f510f918a2c52917ba4e842f1c3"; system: "x86_64-linux";
host version: "75a3413b4e5c1f7443eb944a36ff364f4c4085f4"; pull-version: 1).
Please report it by email to <[email-masked]

To test, apply the patch, and introduce an error in the hash of subversion:

;;; (gnu packages version-control)
(define-public subversion
  (package
    (name "subversion")
    (version "1.14.1")
    (source (origin
             (method url-fetch)
             ;; Oops!
             (uri "http://localhost/nowhere.tar.bz2")
             #;(string-append "mirror://apache/subversion/"
                                 "subversion-" version ".tar.bz2")
             (sha256
              (base32
               ;; Oops! 1->0
               #;"1ag1hvcm9q92kgalzbbgcsq9clxnzmbj9nciz9lmabjx4lyajp9c"
               "0ag1hvcm9q92kgalzbbgcsq9clxnzmbj9nciz9lmabjx4lyajp9c"))))
    (build-system gnu-build-system)
    [...]

and commit that mistake.  Then run
  guix time-machine --branch=master --url=$PWD --disable-authentication

Repeat without the error in subversion.

Greetings,
Maxime
From 9dbcd5cedeb861c27aec2b41fcbe6aba92de6c2e Mon Sep 17 00:00:00 2001
From: Maxime Devos <[email-masked]>
Date: Sat, 28 Aug 2021 14:42:32 +0200
Subject: [PATCH] build-self: Try printing nicer error messages.

This prevents daunting backtraces like in
<https://issues.guix.gnu.org/50232> by only printing
the relevant information: that 'subversion' fails to
build.

* build-aux/self.scm (build-program): Wrap the 'run-with-store'
  in a 'with-error-handling'.
---
 build-aux/build-self.scm | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/build-aux/build-self.scm b/build-aux/build-self.scm
index f100ff4aae..1dbaf52061 100644
--- a/build-aux/build-self.scm
+++ b/build-aux/build-self.scm
@@ -1,5 +1,6 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2014, 2016, 2017, 2018, 2019, 2020, 2021 Ludovic Courtès <[email-masked]>
+;;; Copyright © 2021 Maxime Devos <[email-masked]>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -280,6 +281,7 @@ interface (FFI) of Guile.")
 
                            ,@(source-module-closure `((guix store)
                                                       (guix self)
+                                                      (guix ui)
                                                       (guix derivations)
                                                       (gnu packages bootstrap))
                                                     (list source)
@@ -316,6 +318,7 @@ interface (FFI) of Guile.")
                         (read-disable 'positions))
 
                       (use-modules (guix store)
+                                   (guix ui)
                                    (guix self)
                                    (guix derivations)
                                    (srfi srfi-1))
@@ -347,14 +350,18 @@ interface (FFI) of Guile.")
                              (parameterize ((current-warning-port
                                              (%make-void-port "w"))
                                             (current-build-output-port sock))
-                               (run-with-store store
-                                 (guix-derivation source version
-                                                  #$guile-version
-                                                  #:channel-metadata
-                                                  '#$channel-metadata
-                                                  #:pull-version
-                                                  #$pull-version)
-                                 #:system system))
+                               ;; Use 'with-error-handling' to prevent scary
+                               ;; backtraced like
+                               ;; <https://issues.guix.gnu.org/50232>.
+                               (with-error-handling
+                                 (run-with-store store
+                                   (guix-derivation source version
+                                                    #$guile-version
+                                                    #:channel-metadata
+                                                    '#$channel-metadata
+                                                    #:pull-version
+                                                    #$pull-version)
+                                   #:system system)))
                              derivation-file-name))))))
                   #:module-path (list source))))

base-commit: b4d132f98e03fae559db832e88897f1e166c4d47
prerequisite-patch-id: 91a26ba19372112a11a0eea2b066d2f63641deb1
-- 
2.33.0