Squelching all byte and native compilation warnings from batch package installation

Question

I have to copy my .emacs.d to different computers a lot, so I keep init.el etc in version control and pair it with a batch Elisp script that re-downloads all of my selected packages. I'd like this script to be less noisy, and in particular I'd like it to not bother me with compilation diagnostics for packages that I have no interest in hacking on.

I tried to squelch all the warnings like so:

(package-refresh-contents)
(let ((package-native-compile t)
      (byte-compile-warnings nil)
      (native-comp-async-report-warnings-errors nil))
  (package-install-selected-packages t)

  ;; Block until native compilation has finished.
  (while (or comp-files-queue
             (> (comp-async-runnings) 0))
    (sleep-for 1)))

...but this (specifically, the let-binding of byte-compile-warnings and native-comp-async-report-warnings-errors) appears to have no effect (it's possible that it is suppressing some warnings, but not the particular ones that flood my terminal). What should I be doing instead of, or in addition to, this?

Note: the bootstrap script is not itself byte-compiled, and does not use lexical binding mode.

Note: examples of the warnings I'm still seeing with this code:

json-snatcher.el:222:25: Warning: value returned from (match-end 0) is unused
polymode-core:0: Warning: Not registering prefix "pm".  Affects: (...)
Warning (comp): mime-w3.el:52:45: Warning: reference to free variable ‘w3-mode-map’
Warning (comp): mime-w3.el:62:21: Warning: Use ‘with-current-buffer’ rather than save-excursion+set-buffer
Warning (comp): mime-w3.el:50:12: Warning: the function ‘w3-region’ is not known to be defined.Warning (comp): web-mode.el:11455:36: Warning: Unused lexical variable `end'

P.S. If anyone knows how to cut down the spew generated by package-install itself, that'd also be great. Ideally I would like to see just "Package ‘foo’ installed" for each package, and not the rest of this:

Contacting host: melpa.org:443
Parsing tar file...
Parsing tar file...done
Extracting... \
Extracting...done
  INFO     Scraping files for cython-mode-autoloads.el...
  INFO     Scraping files for cython-mode-autoloads.el...done
Checking .../elpa/cython-mode-20221130.1257...
Compiling .../elpa/cython-mode-20221130.1257/cython-mode-autoloads.el...
Compiling .../elpa/cython-mode-20221130.1257/cython-mode-pkg.el...
Compiling .../elpa/cython-mode-20221130.1257/cython-mode.el...
Done (Total of 1 file compiled, 2 skipped)
Package ‘cython-mode’ installed.

Answer 1

[Not a complete answer: I don't have native compilation set up, so I cannot say anything about that part of it]

I tried the following script:

(message "FOO/")
(require 'package)
(add-to-list 'package-archives
             ;; choose either the stable or the latest git version:
             ;;'("melpa-stable" . "http://melpa-stable.org/packages/")
             '("melpa-unstable" . "http://melpa.org/packages/")
             )

(package-refresh-contents)
(setq package-selected-packages '(json-snatcher))
(message "%S" package-selected-packages)
(let ((byte-compile-warnings nil))       ;; or t
  (package-install-selected-packages t))
(message "/FOO")

and the following command line:

emacs -batch -l /tmp/foo.el

When I tried it with byte-compile-warnings set to t, I get the following output (complete):

FOO/
Importing package-keyring.gpg...
Importing package-keyring.gpg...done
Contacting host: melpa.org:80
Contacting host: melpa.org:80
Package refresh done
Contacting host: elpa.gnu.org:443
Package refresh done
Contacting host: elpa.nongnu.org:443
Package refresh done
(json-snatcher)
Contacting host: melpa.org:80
Parsing tar file... 
Parsing tar file...done
Extracting... \ 
Extracting...done
  INFO     Scraping files for loaddefs... 
  INFO     Scraping files for loaddefs...done
  GEN      json-snatcher-autoloads.el
Checking /home/nick/.config/emacs/elpa/json-snatcher-20200916.1717...
Compiling /home/nick/.config/emacs/elpa/json-snatcher-20200916.1717/json-snatcher-autoloads.el...
Compiling /home/nick/.config/emacs/elpa/json-snatcher-20200916.1717/json-snatcher-pkg.el...
Compiling /home/nick/.config/emacs/elpa/json-snatcher-20200916.1717/json-snatcher.el...

In toplevel form:
json-snatcher.el:79:2: Warning: defvar `jsons-parsed-regions' docstring wider than 80 characters

In jsons-get-path:
json-snatcher.el:205:2: Warning: docstring wider than 80 characters

In jsons-is-number:
json-snatcher.el:225:6: Warning: value from call to ‘match-end’ is unused
json-snatcher.el:229:14: Warning: value from call to ‘match-end’ is unused

In jsons-print-to-buffer:
json-snatcher.el:250:2: Warning: docstring wider than 80 characters

In jsons-print-path-python:
json-snatcher.el:308:2: Warning: docstring wider than 80 characters
Done (Total of 1 file compiled, 2 skipped)
Package ‘json-snatcher’ installed.
/FOO

With byte-compile-warnings set to nil I get this:

FOO/
Importing package-keyring.gpg...
Importing package-keyring.gpg...done
Contacting host: melpa.org:80
Contacting host: melpa.org:80
Package refresh done
Contacting host: elpa.gnu.org:443
Package refresh done
Package refresh done
(json-snatcher)
Contacting host: melpa.org:80
Parsing tar file... 
Parsing tar file...done
Extracting... \ 
Extracting...done
  INFO     Scraping files for loaddefs... 
  INFO     Scraping files for loaddefs...done
  GEN      json-snatcher-autoloads.el
Checking /home/nick/.config/emacs/elpa/json-snatcher-20200916.1717...
Compiling /home/nick/.config/emacs/elpa/json-snatcher-20200916.1717/json-snatcher-autoloads.el...
Compiling /home/nick/.config/emacs/elpa/json-snatcher-20200916.1717/json-snatcher-pkg.el...
Compiling /home/nick/.config/emacs/elpa/json-snatcher-20200916.1717/json-snatcher.el...
Done (Total of 1 file compiled, 2 skipped)
Package ‘json-snatcher’ installed.
/FOO

So it certainly makes a difference. I suspect that the messages you are seeing (in your example) are from native compilation (e.g. the first one about json-snatcher looks different from any of the ones I get from byte compilation), but I can't help with that.

As for the messages from package-install, you might be able to shut them off through Emacs means, but it is easier to use the shell. All of them are produced through message and, in batch mode, they are all redirected to stderr, so you can do something like this to shut them all off:

  emacs -batch -l /tmp/foo.el 2>/dev/null

or if you want to see the installed message, do this:

 emacs -batch -l /tmp/foo.el 2>&1 | grep 'Package .* installed\.'

which produces just this output:

Package ‘json-snatcher’ installed.

You can also play around with the regexp if you want to see a bit more. That's assuming some sort of Unix shell available and I/O redirection to match: I don't know what Emacs does on Windows and whether you can do this in WSL e.g. but it should work fine on Linux and other Unixes (including macOS).