Add "export" to Nix

This adds a ‘nix export’ command which hooks into nix-bundle. It can
be used in a similar way as nix-bundle, with the benefit of hooking
into the new “app” functionality. For instance,

$ nix export nixpkgs#jq
$ ./jq --help
jq - commandline JSON processor [version 1.6]
...
$ scp jq machine-without-nix:
$ ssh machine-without-nix ./jq
jq - commandline JSON processor [version 1.6]
...

Note that nix-bundle currently requires Linux to run. Other exporters
might not have that requirement.

“exporters” are meant to be reusable, so that, other repos can
implement their own bundling.

Fixes #3705
This commit is contained in:
Matthew Bauer 2020-07-30 11:33:22 -05:00
parent c159f48a39
commit 2f4250a416
2 changed files with 151 additions and 0 deletions

126
src/nix/export.cc Normal file
View file

@ -0,0 +1,126 @@
#include "command.hh"
#include "common-args.hh"
#include "shared.hh"
#include "store-api.hh"
#include "fs-accessor.hh"
using namespace nix;
struct CmdExport : InstallableCommand
{
std::string exporter = "github:matthewbauer/nix-bundle";
Path outLink;
CmdExport()
{
addFlag({
.longName = "exporter",
.description = "use custom exporter",
.labels = {"flake-url"},
.handler = {&exporter},
.completer = {[&](size_t, std::string_view prefix) {
completeFlakeRef(getStore(), prefix);
}}
});
addFlag({
.longName = "out-link",
.shortName = 'o',
.description = "path of the symlink to the build result",
.labels = {"path"},
.handler = {&outLink},
.completer = completePath
});
}
std::string description() override
{
return "export an application out of the Nix store";
}
Examples examples() override
{
return {
Example{
"To export Hello:",
"nix export hello"
},
};
}
Strings getDefaultFlakeAttrPaths() override
{
Strings res{"defaultApp." + settings.thisSystem.get()};
for (auto & s : SourceExprCommand::getDefaultFlakeAttrPaths())
res.push_back(s);
return res;
}
Strings getDefaultFlakeAttrPathPrefixes() override
{
Strings res{"apps." + settings.thisSystem.get() + ".", "packages"};
for (auto & s : SourceExprCommand::getDefaultFlakeAttrPathPrefixes())
res.push_back(s);
return res;
}
void run(ref<Store> store) override
{
auto evalState = getEvalState();
auto app = installable->toApp(*evalState);
store->buildPaths(app.context);
auto [exporterFlakeRef, exporterName] = parseFlakeRefWithFragment(exporter, absPath("."));
const flake::LockFlags lockFlags{ .writeLockFile = false };
auto exporter = InstallableFlake(
evalState, std::move(exporterFlakeRef),
Strings{exporterName == "" ? ("defaultExporter." + settings.thisSystem.get()) : exporterName},
Strings({"exporters." + settings.thisSystem.get() + "."}), lockFlags);
Value * arg = evalState->allocValue();
evalState->mkAttrs(*arg, 1);
PathSet context;
for (auto & i : app.context)
context.insert("=" + store->printStorePath(i.path));
mkString(*evalState->allocAttr(*arg, evalState->symbols.create("program")), app.program, context);
auto vRes = evalState->allocValue();
evalState->callFunction(*exporter.toValue(*evalState).first, *arg, *vRes, noPos);
if (!evalState->isDerivation(*vRes))
throw Error("the exporter '%s' does not produce a derivation", exporter.what());
Bindings::iterator i = vRes->attrs->find(evalState->sDrvPath);
if (i == vRes->attrs->end())
throw Error("the exporter '%s' does not produce a derivation", exporter.what());
PathSet context2;
StorePath drvPath = store->parseStorePath(evalState->coerceToPath(*i->pos, *i->value, context2));
i = vRes->attrs->find(evalState->sOutPath);
if (i == vRes->attrs->end())
throw Error("the exporter '%s' does not produce a derivation", exporter.what());
StorePath outPath = store->parseStorePath(evalState->coerceToPath(*i->pos, *i->value, context2));
store->buildPaths({{drvPath}});
auto accessor = store->getFSAccessor();
auto outPathS = store->printStorePath(outPath);
if (accessor->stat(outPathS).type != FSAccessor::tRegular)
throw Error("'%s' is not a file; an exporter must only create a single file", outPathS);
auto info = store->queryPathInfo(outPath);
if (!info->references.empty())
throw Error("'%s' has references; an exporter must not leave any references", outPathS);
if (outLink == "")
outLink = baseNameOf(app.program);
store.dynamic_pointer_cast<LocalFSStore>()->addPermRoot(outPath, absPath(outLink), true);
}
};
static auto r2 = registerCommand<CmdExport>("export");

View file

@ -368,6 +368,21 @@ struct CmdFlakeCheck : FlakeCommand
}
};
auto checkExporter = [&](const std::string & attrPath, Value & v, const Pos & pos) {
try {
state->forceValue(v, pos);
if (v.type != tLambda)
throw Error("exporter must be a function");
if (!v.lambda.fun->formals ||
v.lambda.fun->formals->argNames.find(state->symbols.create("program")) == v.lambda.fun->formals->argNames.end() ||
v.lambda.fun->formals->argNames.find(state->symbols.create("args")) == v.lambda.fun->formals->argNames.end())
throw Error("exporter must take formal arguments 'program' and 'args'");
} catch (Error & e) {
e.addTrace(pos, hintfmt("while checking the template '%s'", attrPath));
throw;
}
};
{
Activity act(*logger, lvlInfo, actUnknown, "evaluating flake");
@ -490,6 +505,16 @@ struct CmdFlakeCheck : FlakeCommand
*attr.value, *attr.pos);
}
else if (name == "defaultExporter")
checkExporter(name, vOutput, pos);
else if (name == "exporters") {
state->forceAttrs(vOutput, pos);
for (auto & attr : *vOutput.attrs)
checkExporter(fmt("%s.%s", name, attr.name),
*attr.value, *attr.pos);
}
else
warn("unknown flake output '%s'", name);