lix/tests/unit
eldritch horrors 512c1f05c3 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 0fa08b4516, )

===

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 df84dd4d8d)

Change-Id: I7cca6b4b53cd0642f2d49af657d5676a8554c9f8
2024-03-09 03:50:06 +01:00
..
libexpr Unify and refactor value printing 2024-03-09 03:50:06 +01:00
libexpr-support Add missing -pthread for test support libraries 2023-12-05 23:44:41 +00:00
libstore Merge pull request #9560 from obsidiansystems/serve-proto-unkeyed-valid-path-info-serializer 2024-03-07 12:37:33 +01:00
libstore-support Merge pull request #10074 from lf-/jade/ban-implicit-fallthrough 2024-03-07 00:11:12 -07:00
libutil fix: nlohmann::adl_serializer for std::optional (#9147) 2024-03-04 07:11:25 +01:00
libutil-support Add missing -pthread for test support libraries 2023-12-05 23:44:41 +00:00