nix-super/src/libexpr/primops/fetchTree.cc
John Ericson cede94dbf7 builtins.fetchTree: Mark experimental the new way
This helps ensure uniform docs/error message.
2023-09-28 20:51:25 -04:00

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#include "primops.hh"
#include "eval-inline.hh"
#include "eval-settings.hh"
#include "store-api.hh"
#include "fetchers.hh"
#include "filetransfer.hh"
#include "registry.hh"
#include "url.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.isLocked());
auto attrs = state.buildBindings(10);
state.mkStorePathString(tree.storePath, attrs.alloc(state.sOutPath));
// FIXME: support arbitrary input attributes.
auto narHash = input.getNarHash();
assert(narHash);
attrs.alloc("narHash").mkString(narHash->to_string(SRI, true));
if (input.getType() == "git")
attrs.alloc("submodules").mkBool(
fetchers::maybeGetBoolAttr(input.attrs, "submodules").value_or(false));
if (!forceDirty) {
if (auto rev = input.getRev()) {
attrs.alloc("rev").mkString(rev->gitRev());
attrs.alloc("shortRev").mkString(rev->gitShortRev());
} else if (emptyRevFallback) {
// Backwards compat for `builtins.fetchGit`: dirty repos return an empty sha1 as rev
auto emptyHash = Hash(htSHA1);
attrs.alloc("rev").mkString(emptyHash.gitRev());
attrs.alloc("shortRev").mkString(emptyHash.gitShortRev());
}
if (auto revCount = input.getRevCount())
attrs.alloc("revCount").mkInt(*revCount);
else if (emptyRevFallback)
attrs.alloc("revCount").mkInt(0);
}
if (auto dirtyRev = fetchers::maybeGetStrAttr(input.attrs, "dirtyRev")) {
attrs.alloc("dirtyRev").mkString(*dirtyRev);
attrs.alloc("dirtyShortRev").mkString(*fetchers::maybeGetStrAttr(input.attrs, "dirtyShortRev"));
}
if (auto lastModified = input.getLastModified()) {
attrs.alloc("lastModified").mkInt(*lastModified);
attrs.alloc("lastModifiedDate").mkString(
fmt("%s", std::put_time(std::gmtime(&*lastModified), "%Y%m%d%H%M%S")));
}
v.mkAttrs(attrs);
}
std::string fixURI(std::string uri, EvalState & state, const std::string & defaultScheme = "file")
{
state.checkURI(uri);
if (uri.find("://") == std::string::npos) {
const auto p = ParsedURL {
.scheme = defaultScheme,
.authority = "",
.path = uri
};
return p.to_string();
} else {
return uri;
}
}
std::string fixURIForGit(std::string uri, EvalState & state)
{
/* Detects scp-style uris (e.g. git@github.com:NixOS/nix) and fixes
* them by removing the `:` and assuming a scheme of `ssh://`
* */
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 PosIdx pos,
Value * * args,
Value & v,
std::optional<std::string> type,
const FetchTreeParams & params = FetchTreeParams{}
) {
fetchers::Input input;
NixStringContext context;
state.forceValue(*args[0], pos);
if (args[0]->type() == nAttrs) {
state.forceAttrs(*args[0], pos, "while evaluating the argument passed to builtins.fetchTree");
fetchers::Attrs attrs;
if (auto aType = args[0]->attrs->get(state.sType)) {
if (type)
state.debugThrowLastTrace(EvalError({
.msg = hintfmt("unexpected attribute 'type'"),
.errPos = state.positions[pos]
}));
type = state.forceStringNoCtx(*aType->value, aType->pos, "while evaluating the `type` attribute passed to builtins.fetchTree");
} else if (!type)
state.debugThrowLastTrace(EvalError({
.msg = hintfmt("attribute 'type' is missing in call to 'fetchTree'"),
.errPos = state.positions[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).toOwned();
attrs.emplace(state.symbols[attr.name],
state.symbols[attr.name] == "url"
? type == "git"
? fixURIForGit(s, state)
: fixURI(s, state)
: s);
}
else if (attr.value->type() == nBool)
attrs.emplace(state.symbols[attr.name], Explicit<bool>{attr.value->boolean});
else if (attr.value->type() == nInt)
attrs.emplace(state.symbols[attr.name], uint64_t(attr.value->integer));
else
state.debugThrowLastTrace(TypeError("fetchTree argument '%s' is %s while a string, Boolean or integer is expected",
state.symbols[attr.name], showType(*attr.value)));
}
if (!params.allowNameArgument)
if (auto nameIter = attrs.find("name"); nameIter != attrs.end())
state.debugThrowLastTrace(EvalError({
.msg = hintfmt("attribute 'name' isnt supported in call to 'fetchTree'"),
.errPos = state.positions[pos]
}));
input = fetchers::Input::fromAttrs(std::move(attrs));
} else {
auto url = state.coerceToString(pos, *args[0], context,
"while evaluating the first argument passed to the fetcher",
false, false).toOwned();
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.isLocked())
state.debugThrowLastTrace(EvalError("in pure evaluation mode, 'fetchTree' requires a locked input, at %s", state.positions[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 PosIdx pos, Value * * args, Value & v)
{
fetchTree(state, pos, args, v, std::nullopt, FetchTreeParams { .allowNameArgument = false });
}
static RegisterPrimOp primop_fetchTree({
.name = "fetchTree",
.args = {"input"},
.doc = R"(
Fetch a source tree or a plain file using one of the supported backends.
*input* can be an attribute set representation of [flake reference](@docroot@/command-ref/new-cli/nix3-flake.md#flake-references) or a URL.
The input should be "locked", that is, it should contain a commit hash or content hash unless impure evaluation (`--impure`) is allowed.
Here are some examples of how to use `fetchTree`:
- Fetch a GitHub repository:
```nix
builtins.fetchTree {
type = "github";
owner = "NixOS";
repo = "nixpkgs";
rev = "ae2e6b3958682513d28f7d633734571fb18285dd";
}
```
This evaluates to attribute set:
```
{
lastModified = 1686503798;
lastModifiedDate = "20230611171638";
narHash = "sha256-rA9RqKP9OlBrgGCPvfd5HVAXDOy8k2SmPtB/ijShNXc=";
outPath = "/nix/store/l5m6qlvfs9sdw14ja3qbzpglcjlb6j1x-source";
rev = "ae2e6b3958682513d28f7d633734571fb18285dd";
shortRev = "ae2e6b3";
}
```
- Fetch a single file from a URL:
```nix
builtins.fetchTree "https://example.com/"
```
)",
.fun = prim_fetchTree,
.experimentalFeature = Xp::Flakes,
});
static void fetch(EvalState & state, const PosIdx pos, Value * * args, Value & v,
const std::string & who, bool unpack, std::string name)
{
std::optional<std::string> url;
std::optional<Hash> expectedHash;
state.forceValue(*args[0], pos);
if (args[0]->type() == nAttrs) {
for (auto & attr : *args[0]->attrs) {
std::string_view n(state.symbols[attr.name]);
if (n == "url")
url = state.forceStringNoCtx(*attr.value, attr.pos, "while evaluating the url we should fetch");
else if (n == "sha256")
expectedHash = newHashAllowEmpty(state.forceStringNoCtx(*attr.value, attr.pos, "while evaluating the sha256 of the content we should fetch"), htSHA256);
else if (n == "name")
name = state.forceStringNoCtx(*attr.value, attr.pos, "while evaluating the name of the content we should fetch");
else
state.debugThrowLastTrace(EvalError({
.msg = hintfmt("unsupported argument '%s' to '%s'", n, who),
.errPos = state.positions[attr.pos]
}));
}
if (!url)
state.debugThrowLastTrace(EvalError({
.msg = hintfmt("'url' argument required"),
.errPos = state.positions[pos]
}));
} else
url = state.forceStringNoCtx(*args[0], pos, "while evaluating the url we should fetch");
if (who == "fetchTarball")
url = evalSettings.resolvePseudoUrl(*url);
state.checkURI(*url);
if (name == "")
name = baseNameOf(*url);
if (evalSettings.pureEval && !expectedHash)
state.debugThrowLastTrace(EvalError("in pure evaluation mode, '%s' requires a 'sha256' argument", who));
// early exit if pinned and already in the store
if (expectedHash && expectedHash->type == htSHA256) {
auto expectedPath = state.store->makeFixedOutputPath(
name,
FixedOutputInfo {
.method = unpack ? FileIngestionMethod::Recursive : FileIngestionMethod::Flat,
.hash = *expectedHash,
.references = {}
});
if (state.store->isValidPath(expectedPath)) {
state.allowAndSetStorePathString(expectedPath, v);
return;
}
}
// TODO: fetching may fail, yet the path may be substitutable.
// https://github.com/NixOS/nix/issues/4313
auto storePath =
unpack
? fetchers::downloadTarball(state.store, *url, name, (bool) expectedHash).tree.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)
state.debugThrowLastTrace(EvalError((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.allowAndSetStorePathString(storePath, v);
}
static void prim_fetchurl(EvalState & state, const PosIdx 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.
Not available in [restricted evaluation mode](@docroot@/command-ref/conf-file.md#conf-restrict-eval).
)",
.fun = prim_fetchurl,
});
static void prim_fetchTarball(EvalState & state, const PosIdx 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 `--tarball-ttl`
*number-of-seconds* or in the Nix configuration file by adding
the line `tarball-ttl = ` *number-of-seconds*.
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 { }
```
Not available in [restricted evaluation mode](@docroot@/command-ref/conf-file.md#conf-restrict-eval).
)",
.fun = prim_fetchTarball,
});
static void prim_fetchGit(EvalState & state, const PosIdx 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` (default: *basename of the URL*)
The name of the directory the repo should be exported to in the store.
- `rev` (default: *the tip of `ref`*)
The [Git revision] to fetch.
This is typically a commit hash.
[Git revision]: https://git-scm.com/docs/git-rev-parse#_specifying_revisions
- `ref` (default: `HEAD`)
The [Git reference] under which to look for the requested revision.
This is often a branch or tag name.
[Git reference]: https://git-scm.com/book/en/v2/Git-Internals-Git-References
By default, the `ref` value is prefixed with `refs/heads/`.
As of 2.3.0, Nix will not prefix `refs/heads/` if `ref` starts with `refs/`.
- `submodules` (default: `false`)
A Boolean parameter that specifies whether submodules should be checked out.
- `shallow` (default: `false`)
A Boolean parameter that specifies whether fetching a shallow clone is allowed.
- `allRefs`
Whether to fetch all references 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";
}
```
Nix will refetch the branch according to the [`tarball-ttl`](@docroot@/command-ref/conf-file.md#conf-tarball-ttl) setting.
This behavior is disabled in [pure evaluation mode](@docroot@/command-ref/conf-file.md#conf-pure-eval).
- To fetch the content of a checked-out work directory:
```nix
builtins.fetchGit ./work-dir
```
If the URL points to a local directory, and no `ref` or `rev` is
given, `fetchGit` will use the current content of the checked-out
files, even if they are not committed or added to Git's index. It will
only consider files added to the Git repository, as listed by `git ls-files`.
)",
.fun = prim_fetchGit,
});
}