From 512c1f05c37c612347dd1fda4771a09744a1a3cd Mon Sep 17 00:00:00 2001 From: eldritch horrors Date: Fri, 8 Mar 2024 03:05:47 +0100 Subject: Unify and refactor value printing Previously, there were two mostly-identical value printers -- one in `libexpr/eval.cc` (which didn't force values) and one in `libcmd/repl.cc` (which did force values and also printed ANSI color codes). This PR unifies both of these printers into `print.cc` and provides a `PrintOptions` struct for controlling the output, which allows for toggling whether values are forced, whether repeated values are tracked, and whether ANSI color codes are displayed. Additionally, `PrintOptions` allows tuning the maximum number of attributes, list items, and bytes in a string that will be displayed; this makes it ideal for contexts where printing too much output (e.g. all of Nixpkgs) is distracting. (As requested by @roberth in https://github.com/NixOS/nix/pull/9554#issuecomment-1845095735) Please read the tests for example output. Future work: - It would be nice to provide this function as a builtin, perhaps `builtins.toStringDebug` -- a printing function that never fails would be useful when debugging Nix code. - It would be nice to support customizing `PrintOptions` members on the command line, e.g. `--option to-string-max-attrs 1000`. (cherry picked from commit 0fa08b451682fb3311fe58112ff05c4fe5bee3a4, ) === Restore ambiguous value printer for `nix-instantiate` The Nix team has requested that this output format remain unchanged. I've added a warning to the man page explaining that `nix-instantiate --eval` output will not parse correctly in many situations. (cherry picked from commit df84dd4d8dd3fd6381ac2ca3064432ab31a16b79) Change-Id: I7cca6b4b53cd0642f2d49af657d5676a8554c9f8 --- src/libutil/english.hh | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) create mode 100644 src/libutil/english.hh (limited to 'src/libutil/english.hh') diff --git a/src/libutil/english.hh b/src/libutil/english.hh new file mode 100644 index 000000000..9c6c93571 --- /dev/null +++ b/src/libutil/english.hh @@ -0,0 +1,18 @@ +#pragma once + +#include + +namespace nix { + +/** + * Pluralize a given value. + * + * If `count == 1`, prints `1 {single}` to `output`, otherwise prints `{count} {plural}`. + */ +std::ostream & pluralize( + std::ostream & output, + unsigned int count, + const std::string_view single, + const std::string_view plural); + +} -- cgit v1.2.3