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Quote reserved keywords when printing expressions #8110

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merged 3 commits into from
May 9, 2023
Merged

Quote reserved keywords when printing expressions #8110

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b72bc4a
libexpr: quote reserved keys when printing
aakropotkin May 9, 2023
82296f8
prevent double quotation
aakropotkin May 9, 2023
82d1d74
quote subshell expansion in tests/eval.sh
aakropotkin May 9, 2023
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1 change: 0 additions & 1 deletion src/libexpr/eval.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -94,7 +94,6 @@ RootValue allocRootValue(Value * v)
#endif
}


void Value::print(const SymbolTable & symbols, std::ostream & str,
std::set<const void *> * seen) const
{
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20 changes: 18 additions & 2 deletions src/libexpr/print.cc
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@@ -1,4 +1,5 @@
#include "print.hh"
#include <unordered_set>

namespace nix {

Expand All @@ -25,11 +26,26 @@ printLiteralBool(std::ostream & str, bool boolean)
return str;
}

// Returns `true' is a string is a reserved keyword which requires quotation
// when printing attribute set field names.
//
// This list should generally be kept in sync with `./lexer.l'.
// You can test if a keyword needs to be added by running:
// $ nix eval --expr '{ <KEYWORD> = 1; }'
// For example `or' doesn't need to be quoted.
bool isReservedKeyword(const std::string_view str)
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Hmm, technically reserved keywords would be keywords that aren't in use. I don't think Nix has any of those.
IIRC JavaScript reserved some Java/C/C++ keywords early on, that remain reserved and unused until this day.

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Want to rename it?

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When anyone has time.

{
static const std::unordered_set<std::string_view> reservedKeywords = {
"if", "then", "else", "assert", "with", "let", "in", "rec", "inherit"
};
return reservedKeywords.contains(str);
}

std::ostream &
printIdentifier(std::ostream & str, std::string_view s) {
if (s.empty())
str << "\"\"";
else if (s == "if") // FIXME: handle other keywords
else if (isReservedKeyword(s))
str << '"' << s << '"';
else {
char c = s[0];
Expand All @@ -50,10 +66,10 @@ printIdentifier(std::ostream & str, std::string_view s) {
return str;
}

// FIXME: keywords
static bool isVarName(std::string_view s)
{
if (s.size() == 0) return false;
if (isReservedKeyword(s)) return false;
char c = s[0];
if ((c >= '0' && c <= '9') || c == '-' || c == '\'') return false;
for (auto & i : s)
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6 changes: 6 additions & 0 deletions src/libexpr/print.hh
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Expand Up @@ -35,6 +35,12 @@ namespace nix {
*/
std::ostream & printAttributeName(std::ostream & o, std::string_view s);

/**
* Returns `true' is a string is a reserved keyword which requires quotation
* when printing attribute set field names.
*/
bool isReservedKeyword(const std::string_view str);

/**
* Print a string as an identifier in the Nix expression language syntax.
*
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6 changes: 4 additions & 2 deletions tests/eval.sh
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Expand Up @@ -16,19 +16,21 @@ nix eval --expr 'assert 1 + 2 == 3; true'
[[ $(nix eval int -f "./eval.nix") == 123 ]]
[[ $(nix eval str -f "./eval.nix") == '"foo"' ]]
[[ $(nix eval str --raw -f "./eval.nix") == 'foo' ]]
[[ $(nix eval attr -f "./eval.nix") == '{ foo = "bar"; }' ]]
[[ "$(nix eval attr -f "./eval.nix")" == '{ foo = "bar"; }' ]]
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[[ $(nix eval attr --json -f "./eval.nix") == '{"foo":"bar"}' ]]
[[ $(nix eval int -f - < "./eval.nix") == 123 ]]
[[ "$(nix eval --expr '{"assert"=1;bar=2;}')" == '{ "assert" = 1; bar = 2; }' ]]

# Check if toFile can be utilized during restricted eval
[[ $(nix eval --restrict-eval --expr 'import (builtins.toFile "source" "42")') == 42 ]]

nix-instantiate --eval -E 'assert 1 + 2 == 3; true'
[[ $(nix-instantiate -A int --eval "./eval.nix") == 123 ]]
[[ $(nix-instantiate -A str --eval "./eval.nix") == '"foo"' ]]
[[ $(nix-instantiate -A attr --eval "./eval.nix") == '{ foo = "bar"; }' ]]
[[ "$(nix-instantiate -A attr --eval "./eval.nix")" == '{ foo = "bar"; }' ]]
[[ $(nix-instantiate -A attr --eval --json "./eval.nix") == '{"foo":"bar"}' ]]
[[ $(nix-instantiate -A int --eval - < "./eval.nix") == 123 ]]
[[ "$(nix-instantiate --eval -E '{"assert"=1;bar=2;}')" == '{ "assert" = 1; bar = 2; }' ]]

# Check that symlink cycles don't cause a hang.
ln -sfn cycle.nix $TEST_ROOT/cycle.nix
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