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lix/src/libexpr/primops/fetchTree.cc
Kevin Amado e5a27a3b4e
fetchTree: add pos to EvalState::forceValue 
- This way we improve error messages
  on infinite recursion
- Demo:
  ```nix
  let x = builtins.fetchTree {
    type = "git";
    inherit x;
  };
  in x
  ```
- Before:
  ```bash
  $ nix-instantiate --extra-experimental-features flakes --strict
  error: infinite recursion encountered
  ```
- After:
  ```bash
  $ nix-instantiate --extra-experimental-features flakes --strict
  error: infinite recursion encountered

       at /data/github/kamadorueda/nix/test.nix:3:10:

            2|   type = "git";
            3|   inherit x;
             |          ^
            4| };
  ```

Mentions: #3505
2021-10-15 19:25:19 -05:00

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#include "primops.hh"
#include "eval-inline.hh"
#include "store-api.hh"
#include "fetchers.hh"
#include "filetransfer.hh"
#include "registry.hh"
#include <ctime>
#include <iomanip>
#include <regex>
namespace nix {
void emitTreeAttrs(
EvalState & state,
const fetchers::Tree & tree,
const fetchers::Input & input,
Value & v,
bool emptyRevFallback,
bool forceDirty)
{
assert(input.isImmutable());
state.mkAttrs(v, 8);
auto storePath = state.store->printStorePath(tree.storePath);
mkString(*state.allocAttr(v, state.sOutPath), storePath, PathSet({storePath}));
// FIXME: support arbitrary input attributes.
auto narHash = input.getNarHash();
assert(narHash);
mkString(*state.allocAttr(v, state.symbols.create("narHash")),
narHash->to_string(SRI, true));
if (input.getType() == "git")
mkBool(*state.allocAttr(v, state.symbols.create("submodules")),
fetchers::maybeGetBoolAttr(input.attrs, "submodules").value_or(false));
if (!forceDirty) {
if (auto rev = input.getRev()) {
mkString(*state.allocAttr(v, state.symbols.create("rev")), rev->gitRev());
mkString(*state.allocAttr(v, state.symbols.create("shortRev")), rev->gitShortRev());
} else if (emptyRevFallback) {
// Backwards compat for `builtins.fetchGit`: dirty repos return an empty sha1 as rev
auto emptyHash = Hash(htSHA1);
mkString(*state.allocAttr(v, state.symbols.create("rev")), emptyHash.gitRev());
mkString(*state.allocAttr(v, state.symbols.create("shortRev")), emptyHash.gitShortRev());
}
if (auto revCount = input.getRevCount())
mkInt(*state.allocAttr(v, state.symbols.create("revCount")), *revCount);
else if (emptyRevFallback)
mkInt(*state.allocAttr(v, state.symbols.create("revCount")), 0);
}
if (auto lastModified = input.getLastModified()) {
mkInt(*state.allocAttr(v, state.symbols.create("lastModified")), *lastModified);
mkString(*state.allocAttr(v, state.symbols.create("lastModifiedDate")),
fmt("%s", std::put_time(std::gmtime(&*lastModified), "%Y%m%d%H%M%S")));
}
v.attrs->sort();
}
std::string fixURI(std::string uri, EvalState & state, const std::string & defaultScheme = "file")
{
state.checkURI(uri);
return uri.find("://") != std::string::npos ? uri : defaultScheme + "://" + uri;
}
std::string fixURIForGit(std::string uri, EvalState & state)
{
static std::regex scp_uri("([^/].*)@(.*):(.*)");
if (uri[0] != '/' && std::regex_match(uri, scp_uri))
return fixURI(std::regex_replace(uri, scp_uri, "$1@$2/$3"), state, "ssh");
else
return fixURI(uri, state);
}
struct FetchTreeParams {
bool emptyRevFallback = false;
bool allowNameArgument = false;
};
static void fetchTree(
EvalState & state,
const Pos & pos,
Value * * args,
Value & v,
std::optional<std::string> type,
const FetchTreeParams & params = FetchTreeParams{}
) {
fetchers::Input input;
PathSet context;
state.forceValue(*args[0], pos);
if (args[0]->type() == nAttrs) {
state.forceAttrs(*args[0], pos);
fetchers::Attrs attrs;
if (auto aType = args[0]->attrs->get(state.sType)) {
if (type)
throw Error({
.msg = hintfmt("unexpected attribute 'type'"),
.errPos = pos
});
type = state.forceStringNoCtx(*aType->value, *aType->pos);
} else if (!type)
throw Error({
.msg = hintfmt("attribute 'type' is missing in call to 'fetchTree'"),
.errPos = pos
});
attrs.emplace("type", type.value());
for (auto & attr : *args[0]->attrs) {
if (attr.name == state.sType) continue;
state.forceValue(*attr.value, *attr.pos);
if (attr.value->type() == nPath || attr.value->type() == nString) {
auto s = state.coerceToString(*attr.pos, *attr.value, context, false, false);
attrs.emplace(attr.name,
attr.name == "url"
? type == "git"
? fixURIForGit(s, state)
: fixURI(s, state)
: s);
}
else if (attr.value->type() == nBool)
attrs.emplace(attr.name, Explicit<bool>{attr.value->boolean});
else if (attr.value->type() == nInt)
attrs.emplace(attr.name, uint64_t(attr.value->integer));
else
throw TypeError("fetchTree argument '%s' is %s while a string, Boolean or integer is expected",
attr.name, showType(*attr.value));
}
if (!params.allowNameArgument)
if (auto nameIter = attrs.find("name"); nameIter != attrs.end())
throw Error({
.msg = hintfmt("attribute 'name' isn’t supported in call to 'fetchTree'"),
.errPos = pos
});
input = fetchers::Input::fromAttrs(std::move(attrs));
} else {
auto url = state.coerceToString(pos, *args[0], context, false, false);
if (type == "git") {
fetchers::Attrs attrs;
attrs.emplace("type", "git");
attrs.emplace("url", fixURIForGit(url, state));
input = fetchers::Input::fromAttrs(std::move(attrs));
} else {
input = fetchers::Input::fromURL(fixURI(url, state));
}
}
if (!evalSettings.pureEval && !input.isDirect())
input = lookupInRegistries(state.store, input).first;
if (evalSettings.pureEval && !input.isImmutable())
throw Error("in pure evaluation mode, 'fetchTree' requires an immutable input, at %s", pos);
auto [tree, input2] = input.fetch(state.store);
state.allowPath(tree.storePath);
emitTreeAttrs(state, tree, input2, v, params.emptyRevFallback, false);
}
static void prim_fetchTree(EvalState & state, const Pos & pos, Value * * args, Value & v)
{
settings.requireExperimentalFeature("flakes");
fetchTree(state, pos, args, v, std::nullopt, FetchTreeParams { .allowNameArgument = false });
}
// FIXME: document
static RegisterPrimOp primop_fetchTree("fetchTree", 1, prim_fetchTree);
static void fetch(EvalState & state, const Pos & pos, Value * * args, Value & v,
const string & who, bool unpack, std::string name)
{
std::optional<std::string> url;
std::optional<Hash> expectedHash;
state.forceValue(*args[0]);
if (args[0]->type() == nAttrs) {
state.forceAttrs(*args[0], pos);
for (auto & attr : *args[0]->attrs) {
string n(attr.name);
if (n == "url")
url = state.forceStringNoCtx(*attr.value, *attr.pos);
else if (n == "sha256")
expectedHash = newHashAllowEmpty(state.forceStringNoCtx(*attr.value, *attr.pos), htSHA256);
else if (n == "name")
name = state.forceStringNoCtx(*attr.value, *attr.pos);
else
throw EvalError({
.msg = hintfmt("unsupported argument '%s' to '%s'", attr.name, who),
.errPos = *attr.pos
});
}
if (!url)
throw EvalError({
.msg = hintfmt("'url' argument required"),
.errPos = pos
});
} else
url = state.forceStringNoCtx(*args[0], pos);
url = resolveUri(*url);
state.checkURI(*url);
if (name == "")
name = baseNameOf(*url);
if (evalSettings.pureEval && !expectedHash)
throw Error("in pure evaluation mode, '%s' requires a 'sha256' argument", who);
auto storePath =
unpack
? fetchers::downloadTarball(state.store, *url, name, (bool) expectedHash).first.storePath
: fetchers::downloadFile(state.store, *url, name, (bool) expectedHash).storePath;
if (expectedHash) {
auto hash = unpack
? state.store->queryPathInfo(storePath)->narHash
: hashFile(htSHA256, state.store->toRealPath(storePath));
if (hash != *expectedHash)
throw Error((unsigned int) 102, "hash mismatch in file downloaded from '%s':\n specified: %s\n got: %s",
*url, expectedHash->to_string(Base32, true), hash.to_string(Base32, true));
}
state.allowPath(storePath);
auto path = state.store->printStorePath(storePath);
mkString(v, path, PathSet({path}));
}
static void prim_fetchurl(EvalState & state, const Pos & pos, Value * * args, Value & v)
{
fetch(state, pos, args, v, "fetchurl", false, "");
}
static RegisterPrimOp primop_fetchurl({
.name = "__fetchurl",
.args = {"url"},
.doc = R"(
Download the specified URL and return the path of the downloaded
file. This function is not available if [restricted evaluation
mode](../command-ref/conf-file.md) is enabled.
)",
.fun = prim_fetchurl,
});
static void prim_fetchTarball(EvalState & state, const Pos & pos, Value * * args, Value & v)
{
fetch(state, pos, args, v, "fetchTarball", true, "source");
}
static RegisterPrimOp primop_fetchTarball({
.name = "fetchTarball",
.args = {"args"},
.doc = R"(
Download the specified URL, unpack it and return the path of the
unpacked tree. The file must be a tape archive (`.tar`) compressed
with `gzip`, `bzip2` or `xz`. The top-level path component of the
files in the tarball is removed, so it is best if the tarball
contains a single directory at top level. The typical use of the
function is to obtain external Nix expression dependencies, such as
a particular version of Nixpkgs, e.g.
```nix
with import (fetchTarball https://github.com/NixOS/nixpkgs/archive/nixos-14.12.tar.gz) {};
stdenv.mkDerivation { … }
```
The fetched tarball is cached for a certain amount of time (1 hour
by default) in `~/.cache/nix/tarballs/`. You can change the cache
timeout either on the command line with `--option tarball-ttl number
of seconds` or in the Nix configuration file with this option: `
number of seconds to cache `.
Note that when obtaining the hash with ` nix-prefetch-url ` the
option `--unpack` is required.
This function can also verify the contents against a hash. In that
case, the function takes a set instead of a URL. The set requires
the attribute `url` and the attribute `sha256`, e.g.
```nix
with import (fetchTarball {
url = "https://github.com/NixOS/nixpkgs/archive/nixos-14.12.tar.gz";
sha256 = "1jppksrfvbk5ypiqdz4cddxdl8z6zyzdb2srq8fcffr327ld5jj2";
}) {};
stdenv.mkDerivation { … }
```
This function is not available if [restricted evaluation
mode](../command-ref/conf-file.md) is enabled.
)",
.fun = prim_fetchTarball,
});
static void prim_fetchGit(EvalState &state, const Pos &pos, Value **args, Value &v)
{
fetchTree(state, pos, args, v, "git", FetchTreeParams { .emptyRevFallback = true, .allowNameArgument = true });
}
static RegisterPrimOp primop_fetchGit({
.name = "fetchGit",
.args = {"args"},
.doc = R"(
Fetch a path from git. *args* can be a URL, in which case the HEAD
of the repo at that URL is fetched. Otherwise, it can be an
attribute with the following attributes (all except `url` optional):
- url\
The URL of the repo.
- name\
The name of the directory the repo should be exported to in the
store. Defaults to the basename of the URL.
- rev\
The git revision to fetch. Defaults to the tip of `ref`.
- ref\
The git ref to look for the requested revision under. This is
often a branch or tag name. Defaults to `HEAD`.
By default, the `ref` value is prefixed with `refs/heads/`. As
of Nix 2.3.0 Nix will not prefix `refs/heads/` if `ref` starts
with `refs/`.
- submodules\
A Boolean parameter that specifies whether submodules should be
checked out. Defaults to `false`.
- allRefs\
Whether to fetch all refs of the repository. With this argument being
true, it's possible to load a `rev` from *any* `ref` (by default only
`rev`s from the specified `ref` are supported).
Here are some examples of how to use `fetchGit`.
- To fetch a private repository over SSH:
```nix
builtins.fetchGit {
url = "git@github.com:my-secret/repository.git";
ref = "master";
rev = "adab8b916a45068c044658c4158d81878f9ed1c3";
}
```
- To fetch an arbitrary reference:
```nix
builtins.fetchGit {
url = "https://github.com/NixOS/nix.git";
ref = "refs/heads/0.5-release";
}
```
- If the revision you're looking for is in the default branch of
the git repository you don't strictly need to specify the branch
name in the `ref` attribute.
However, if the revision you're looking for is in a future
branch for the non-default branch you will need to specify the
the `ref` attribute as well.
```nix
builtins.fetchGit {
url = "https://github.com/nixos/nix.git";
rev = "841fcbd04755c7a2865c51c1e2d3b045976b7452";
ref = "1.11-maintenance";
}
```
> **Note**
>
> It is nice to always specify the branch which a revision
> belongs to. Without the branch being specified, the fetcher
> might fail if the default branch changes. Additionally, it can
> be confusing to try a commit from a non-default branch and see
> the fetch fail. If the branch is specified the fault is much
> more obvious.
- If the revision you're looking for is in the default branch of
the git repository you may omit the `ref` attribute.
```nix
builtins.fetchGit {
url = "https://github.com/nixos/nix.git";
rev = "841fcbd04755c7a2865c51c1e2d3b045976b7452";
}
```
- To fetch a specific tag:
```nix
builtins.fetchGit {
url = "https://github.com/nixos/nix.git";
ref = "refs/tags/1.9";
}
```
- To fetch the latest version of a remote branch:
```nix
builtins.fetchGit {
url = "ssh://git@github.com/nixos/nix.git";
ref = "master";
}
```
> **Note**
>
> Nix will refetch the branch in accordance with
> the option `tarball-ttl`.
> **Note**
>
> This behavior is disabled in *Pure evaluation mode*.
)",
.fun = prim_fetchGit,
});
}
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