59 lines
1.6 KiB
Markdown
59 lines
1.6 KiB
Markdown
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---
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synopsis: "Eliminate some pretty-printing surprises"
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cls: [1616, 1617, 1618]
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prs: [11100]
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credits: [alois31, roberth]
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category: Improvements
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---
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Some inconsistent and surprising behaviours have been eliminated from the pretty-printing used by the REPL and `nix eval`:
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* Lists and attribute sets that contain only a single item without nested structures are no longer sometimes inappropriately indented in the REPL, depending on internal state of the evaluator.
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* Empty attribute sets and derivations are no longer shown as `«repeated»`, since they are always cheap to print.
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This matches the existing behaviour of `nix-instantiate` on empty attribute sets.
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Empty lists were never printed as `«repeated»` already.
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* The REPL by default does not print nested attribute sets and lists, and indicates elided items with an ellipsis.
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Previously, the ellipsis was printed even when the structure was empty, so that such items do not in fact exist.
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Since this behaviour was confusing, it does not happen any more.
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Before:
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```
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nix-repl> :p let x = 1 + 2; in [ [ x ] [ x ] ]
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[
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[
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3
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]
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[ 3 ]
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]
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nix-repl> let inherit (import <nixpkgs> { }) hello; in [ hello hello ]
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[
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«derivation /nix/store/fqs92lzychkm6p37j7fnj4d65nq9fzla-hello-2.12.1.drv»
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«repeated»
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]
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nix-repl> let x = {}; in [ x ]
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[
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{ ... }
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]
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```
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After:
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```
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nix-repl> :p let x = 1 + 2; in [ [ x ] [ x ] ]
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[
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[ 3 ]
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[ 3 ]
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]
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nix-repl> let inherit (import <nixpkgs> { }) hello; in [ hello hello ]
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[
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«derivation /nix/store/fqs92lzychkm6p37j7fnj4d65nq9fzla-hello-2.12.1.drv»
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«derivation /nix/store/fqs92lzychkm6p37j7fnj4d65nq9fzla-hello-2.12.1.drv»
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]
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nix-repl> let x = {}; in [ x ]
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[
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{ }
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]
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```
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