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nix eval: Add option to write a directory

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This is useful for generating the nix manpages, but it may have other
applications (like generating configuration files without a Nix store).
This commit is contained in:
Eelco Dolstra 2020-12-02 21:25:32 +01:00
parent 148608ba6d
commit df552a2645
2 changed files with 59 additions and 4 deletions
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55
src/nix/eval.cc
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@ -3,6 +3,7 @@
#include "shared.hh"
#include "store-api.hh"
#include "eval.hh"
#include "eval-inline.hh"
#include "json.hh"
#include "value-to-json.hh"
#include "progress-bar.hh"
@ -13,6 +14,7 @@ struct CmdEval : MixJSON, InstallableCommand
{
bool raw = false;
std::optional<std::string> apply;
std::optional<Path> writeTo;
CmdEval()
{
@ -24,6 +26,13 @@ struct CmdEval : MixJSON, InstallableCommand
.labels = {"expr"},
.handler = {&apply},
});
addFlag({
.longName = "write-to",
.description = "write a string or attrset of strings to 'path'",
.labels = {"path"},
.handler = {&writeTo},
});
}
std::string description() override
@ -66,7 +75,7 @@ struct CmdEval : MixJSON, InstallableCommand
auto state = getEvalState();
auto v = installable->toValue(*state).first;
auto [v, pos] = installable->toValue(*state);
PathSet context;
if (apply) {
@ -77,13 +86,51 @@ struct CmdEval : MixJSON, InstallableCommand
v = vRes;
}
if (raw) {
if (writeTo) {
stopProgressBar();
if (pathExists(*writeTo))
throw Error("path '%s' already exists", *writeTo);
std::function<void(Value & v, const Pos & pos, const Path & path)> recurse;
recurse = [&](Value & v, const Pos & pos, const Path & path)
{
state->forceValue(v);
if (v.type == tString)
// FIXME: disallow strings with contexts?
writeFile(path, v.string.s);
else if (v.type == tAttrs) {
if (mkdir(path.c_str(), 0777) == -1)
throw SysError("creating directory '%s'", path);
for (auto & attr : *v.attrs)
try {
if (attr.name == "." || attr.name == "..")
throw Error("invalid file name '%s'", attr.name);
recurse(*attr.value, *attr.pos, path + "/" + std::string(attr.name));
} catch (Error & e) {
e.addTrace(*attr.pos, hintfmt("while evaluating the attribute '%s'", attr.name));
throw;
}
}
else
throw TypeError("value at '%s' is not a string or an attribute set", pos);
};
recurse(*v, pos, *writeTo);
}
else if (raw) {
stopProgressBar();
std::cout << state->coerceToString(noPos, *v, context);
} else if (json) {
}
else if (json) {
JSONPlaceholder jsonOut(std::cout);
printValueAsJSON(*state, true, *v, jsonOut, context);
} else {
}
else {
state->forceValueDeep(*v);
logger->cout("%s", *v);
}

8
tests/pure-eval.sh
View file

@ -16,3 +16,11 @@ nix eval --expr 'assert 1 + 2 == 3; true'
[[ $(nix eval --impure --expr "(import (builtins.fetchurl { url = file://$(pwd)/pure-eval.nix; })).x") == 123 ]]
(! nix eval --expr "(import (builtins.fetchurl { url = file://$(pwd)/pure-eval.nix; })).x")
nix eval --expr "(import (builtins.fetchurl { url = file://$(pwd)/pure-eval.nix; sha256 = \"$(nix hash-file pure-eval.nix --type sha256)\"; })).x"
rm -rf $TEST_ROOT/eval-out
nix eval --store dummy:// --write-to $TEST_ROOT/eval-out --expr '{ x = "foo" + "bar"; y = { z = "bla"; }; }'
[[ $(cat $TEST_ROOT/eval-out/x) = foobar ]]
[[ $(cat $TEST_ROOT/eval-out/y/z) = bla ]]
rm -rf $TEST_ROOT/eval-out
(! nix eval --store dummy:// --write-to $TEST_ROOT/eval-out --expr '{ "." = "bla"; }')