0fa08b4516
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`.
63 lines
1.8 KiB
C++
63 lines
1.8 KiB
C++
#pragma once
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/**
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* @file
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* @brief Common printing functions for the Nix language
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*
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* While most types come with their own methods for printing, they share some
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* functions that are placed here.
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*/
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#include <iostream>
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#include "eval.hh"
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#include "print-options.hh"
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namespace nix {
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/**
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* Print a string as a Nix string literal.
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*
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* Quotes and fairly minimal escaping are added.
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*
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* @param o The output stream to print to
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* @param s The logical string
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*/
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std::ostream & printLiteralString(std::ostream & o, std::string_view s);
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inline std::ostream & printLiteralString(std::ostream & o, const char * s) {
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return printLiteralString(o, std::string_view(s));
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}
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inline std::ostream & printLiteralString(std::ostream & o, const std::string & s) {
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return printLiteralString(o, std::string_view(s));
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}
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/** Print `true` or `false`. */
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std::ostream & printLiteralBool(std::ostream & o, bool b);
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/**
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* Print a string as an attribute name in the Nix expression language syntax.
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*
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* Prints a quoted string if necessary.
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*/
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std::ostream & printAttributeName(std::ostream & o, std::string_view s);
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/**
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* Returns `true' is a string is a reserved keyword which requires quotation
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* when printing attribute set field names.
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*/
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bool isReservedKeyword(const std::string_view str);
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/**
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* Print a string as an identifier in the Nix expression language syntax.
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*
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* FIXME: "identifier" is ambiguous. Identifiers do not have a single
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* textual representation. They can be used in variable references,
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* let bindings, left-hand sides or attribute names in a select
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* expression, or something else entirely, like JSON. Use one of the
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* `print*` functions instead.
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*/
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std::ostream & printIdentifier(std::ostream & o, std::string_view s);
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void printValue(EvalState & state, std::ostream & str, Value & v, PrintOptions options = PrintOptions {});
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}
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