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InstallableFlake::toDerivedPaths(): Support paths and store paths

Browse source 
This makes 'nix build' work on paths (which will be copied to the
store) and store paths (returned as is). E.g. the following flake
output attributes can be built using 'nix build .#foo':

  foo = ./src;
  foo = self.outPath;
  foo = builtins.fetchTarball { ... };
  foo = (builtins.fetchTree { .. }).outPath;
  foo = builtins.fetchTree { .. } + "/README.md";
  foo = builtins.storePath /nix/store/...;

Note that this is potentially risky, e.g.

  foo = /.;

will cause Nix to try to copy the entire file system to the store.

What doesn't work yet:

  foo = self;
  foo = builtins.fetchTree { .. };

because we don't handle attrsets with an outPath attribute in it yet,
and

  foo = builtins.storePath /nix/store/.../README.md;

since result symlinks have to point to a store path currently (rather
than a file inside a store path).

Fixes #7417.
This commit is contained in:
Eelco Dolstra 2022-12-15 23:01:15 +01:00
parent bda879170f
commit 5c97b5a398
3 changed files with 99 additions and 2 deletions
Download patch file Download diff file Expand all files Collapse all files

34
src/libcmd/installables.cc
View file

@ -610,8 +610,38 @@ DerivedPathsWithInfo InstallableFlake::toDerivedPaths()
auto attrPath = attr->getAttrPathStr();
if (!attr->isDerivation())
throw Error("flake output attribute '%s' is not a derivation", attrPath);
if (!attr->isDerivation()) {
// FIXME: use eval cache?
auto v = attr->forceValue();
if (v.type() == nPath) {
PathSet context;
auto storePath = state->copyPathToStore(context, Path(v.path));
return {{
.path = DerivedPath::Opaque {
.path = std::move(storePath),
}
}};
}
else if (v.type() == nString) {
PathSet context;
auto s = state->forceString(v, context);
auto storePath = state->store->maybeParseStorePath(s);
if (storePath && context.count(std::string(s))) {
return {{
.path = DerivedPath::Opaque {
.path = std::move(*storePath),
}
}};
} else
throw Error("flake output attribute '%s' evaluates to a string that does not denote a store path", attrPath);
}
else
throw Error("flake output attribute '%s' is not a derivation or path", attrPath);
}
auto drvPath = attr->forceDerivation();