forked from lix-project/lix
Explain how Nix handles antiquotation of paths
Specifically, explain why Nix does not _re_evaluate paths during a `nix repl` session. This is a thing that bit me while playing around with paths and antiquotation in `nix repl` while reading the Nix language tutorial at https://nix.dev/tutorials/nix-language. Co-authored-by: Valentin Gagarin <valentin.gagarin@tweag.io>
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@ -150,6 +150,20 @@
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recognized as a path. `a.${foo}/b.${bar}` is a syntactically valid division
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operation. `./a.${foo}/b.${bar}` is a path.
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When a path appears in an antiquotation, and is thus coerced into a string,
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the path is first copied into the Nix store and the resulting string is
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the Nix store path. For instance `"${./foo.txt}" will cause `foo.txt` in
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the current directory to be copied into the Nix store and result in the
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string `"/nix/store/<HASH>-foo.txt"`.
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Note that the Nix language assumes that all input files will remain
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_unchanged_ during the course of the Nix expression evaluation.
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If you for example antiquote a file path during a `nix repl` session, and
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then later in the same session, after having changed the file contents,
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evaluate the antiquotation with the file path again, then Nix will still
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return the first store path. It will _not_ reread the file contents to
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produce a different Nix store path.
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- <a id="type-boolean" href="#type-boolean">Boolean</a>
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*Booleans* with values `true` and `false`.
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