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Add path primop.

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builtins.path allows specifying the name of a path (which makes paths
with store-illegal names now addable), allows adding paths with flat
instead of recursive hashes, allows specifying a filter (so is a
generalization of filterSource), and allows specifying an expected
hash (enabling safe path adding in pure mode).
This commit is contained in:
Shea Levy 2018-01-25 07:05:57 -08:00
parent 98f3c75a0e
commit 69d82e5c58
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GPG key ID: 5C0BD6957D86FE27
8 changed files with 162 additions and 27 deletions
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72
doc/manual/expressions/builtins.xml
View file

@ -308,7 +308,8 @@ stdenv.mkDerivation { … }
</varlistentry>
<varlistentry><term><function>builtins.filterSource</function>
<varlistentry xml:id='builtin-filterSource'>
<term><function>builtins.filterSource</function>
<replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
<listitem>
@ -768,6 +769,75 @@ Evaluates to <literal>[ "foo" ]</literal>.
</varlistentry>
<varlistentry>
<term>
<function>builtins.path</function>
<replaceable>args</replaceable>
</term>
<listitem>
<para>
An enrichment of the built-in path type, based on the attributes
present in <replaceable>args</replaceable>. All are optional
except <varname>path</varname>:
</para>
<variablelist>
<varlistentry>
<term>path</term>
<listitem>
<para>The underlying path.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>name</term>
<listitem>
<para>
The name of the path when added to the store. This can
used to reference paths that have nix-illegal characters
in their names, like <literal>@</literal>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>filter</term>
<listitem>
<para>
A function of the type expected by
<link linkend="builtin-filterSource">builtins.filterSource</link>,
with the same semantics.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>recursive</term>
<listitem>
<para>
When <literal>false</literal>, when
<varname>path</varname> is added to the store it is with a
flat hash, rather than a hash of the NAR serialization of
the file. Thus, <varname>path</varname> must refer to a
regular file, not a directory. This allows similar
behavior to <literal>fetchurl</literal>. Defaults to
<literal>true</literal>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>sha256</term>
<listitem>
<para>
When provided, this is the expected hash of the file at
the path. Evaluation will fail if the hash is incorrect,
and providing a hash allows
<literal>builtins.path</literal> to be used even when the
<literal>pure-eval</literal> nix config option is on.
</para>
</listitem>
</varlistentry>
</variablelist>
</listitem>
</varlistentry>
<varlistentry><term><function>builtins.pathExists</function>
<replaceable>path</replaceable></term>

2
src/libexpr/eval.cc
View file

@ -1566,7 +1566,7 @@ string EvalState::copyPathToStore(PathSet & context, const Path & path)
dstPath = srcToStore[path];
else {
dstPath = settings.readOnlyMode
? store->computeStorePathForPath(checkSourcePath(path)).first
? store->computeStorePathForPath(baseNameOf(path), checkSourcePath(path)).first
: store->addToStore(baseNameOf(path), checkSourcePath(path), true, htSHA256, defaultPathFilter, repair);
srcToStore[path] = dstPath;
printMsg(lvlChatty, format("copied source '%1%' -> '%2%'")

93
src/libexpr/primops.cc
View file

@ -1009,20 +1009,13 @@ static void prim_toFile(EvalState & state, const Pos & pos, Value * * args, Valu
}
static void prim_filterSource(EvalState & state, const Pos & pos, Value * * args, Value & v)
static void addPath(EvalState & state, const Pos & pos, const string & name, const Path & path_,
Value * filterFun, bool recursive, const Hash & expectedHash, Value & v)
{
PathSet context;
Path path = state.coerceToPath(pos, *args[1], context);
if (!context.empty())
throw EvalError(format("string '%1%' cannot refer to other paths, at %2%") % path % pos);
state.forceValue(*args[0]);
if (args[0]->type != tLambda)
throw TypeError(format("first argument in call to 'filterSource' is not a function but %1%, at %2%") % showType(*args[0]) % pos);
path = state.checkSourcePath(path);
PathFilter filter = [&](const Path & path) {
const auto path = settings.pureEval && expectedHash ?
path_ :
state.checkSourcePath(path_);
PathFilter filter = filterFun ? ([&](const Path & path) {
auto st = lstat(path);
/* Call the filter function. The first argument is the path,
@ -1031,7 +1024,7 @@ static void prim_filterSource(EvalState & state, const Pos & pos, Value * * args
mkString(arg1, path);
Value fun2;
state.callFunction(*args[0], arg1, fun2, noPos);
state.callFunction(*filterFun, arg1, fun2, noPos);
Value arg2;
mkString(arg2,
@ -1044,16 +1037,79 @@ static void prim_filterSource(EvalState & state, const Pos & pos, Value * * args
state.callFunction(fun2, arg2, res, noPos);
return state.forceBool(res, pos);
};
}) : defaultPathFilter;
Path dstPath = settings.readOnlyMode
? state.store->computeStorePathForPath(path, true, htSHA256, filter).first
: state.store->addToStore(baseNameOf(path), path, true, htSHA256, filter, state.repair);
Path expectedStorePath;
if (expectedHash) {
expectedStorePath =
state.store->makeFixedOutputPath(recursive, expectedHash, name);
}
Path dstPath;
if (!expectedHash || !state.store->isValidPath(expectedStorePath)) {
dstPath = settings.readOnlyMode
? state.store->computeStorePathForPath(name, path, recursive, htSHA256, filter).first
: state.store->addToStore(name, path, recursive, htSHA256, filter, state.repair);
if (expectedHash && expectedStorePath != dstPath) {
throw Error(format("store path mismatch in (possibly filtered) path added from '%1%'") % path);
}
} else
dstPath = expectedStorePath;
mkString(v, dstPath, {dstPath});
}
static void prim_filterSource(EvalState & state, const Pos & pos, Value * * args, Value & v)
{
PathSet context;
Path path = state.coerceToPath(pos, *args[1], context);
if (!context.empty())
throw EvalError(format("string '%1%' cannot refer to other paths, at %2%") % path % pos);
state.forceValue(*args[0]);
if (args[0]->type != tLambda)
throw TypeError(format("first argument in call to 'filterSource' is not a function but %1%, at %2%") % showType(*args[0]) % pos);
addPath(state, pos, baseNameOf(path), path, args[0], true, Hash(), v);
}
static void prim_path(EvalState & state, const Pos & pos, Value * * args, Value & v)
{
state.forceAttrs(*args[0], pos);
Path path;
string name;
Value * filterFun = nullptr;
auto recursive = true;
Hash expectedHash;
for (auto & attr : *args[0]->attrs) {
const string & n(attr.name);
if (n == "path") {
PathSet context;
path = state.coerceToPath(*attr.pos, *attr.value, context);
if (!context.empty())
throw EvalError(format("string '%1%' cannot refer to other paths, at %2%") % path % *attr.pos);
} else if (attr.name == state.sName)
name = state.forceStringNoCtx(*attr.value, *attr.pos);
else if (n == "filter") {
state.forceValue(*attr.value);
filterFun = attr.value;
} else if (n == "recursive")
recursive = state.forceBool(*attr.value, *attr.pos);
else if (n == "sha256")
expectedHash = Hash(state.forceStringNoCtx(*attr.value, *attr.pos), htSHA256);
else
throw EvalError(format("unsupported argument '%1%' to 'addPath', at %2%") % attr.name % *attr.pos);
}
if (path.empty())
throw EvalError(format("'path' required, at %1%") % pos);
if (name.empty())
name = baseNameOf(path);
addPath(state, pos, name, path, filterFun, recursive, expectedHash, v);
}
/*************************************************************
* Sets
*************************************************************/
@ -2071,6 +2127,7 @@ void EvalState::createBaseEnv()
addPrimOp("__fromJSON", 1, prim_fromJSON);
addPrimOp("__toFile", 2, prim_toFile);
addPrimOp("__filterSource", 2, prim_filterSource);
addPrimOp("__path", 1, prim_path);
// Sets
addPrimOp("__attrNames", 1, prim_attrNames);

5
src/libstore/store-api.cc
View file

@ -222,11 +222,10 @@ Path Store::makeTextPath(const string & name, const Hash & hash,
}
std::pair<Path, Hash> Store::computeStorePathForPath(const Path & srcPath,
bool recursive, HashType hashAlgo, PathFilter & filter) const
std::pair<Path, Hash> Store::computeStorePathForPath(const string & name,
const Path & srcPath, bool recursive, HashType hashAlgo, PathFilter & filter) const
{
Hash h = recursive ? hashPath(hashAlgo, srcPath, filter).first : hashFile(hashAlgo, srcPath);
string name = baseNameOf(srcPath);
Path dstPath = makeFixedOutputPath(recursive, h, name);
return std::pair<Path, Hash>(dstPath, h);
}

6
src/libstore/store-api.hh
View file

@ -305,9 +305,9 @@ public:
/* This is the preparatory part of addToStore(); it computes the
store path to which srcPath is to be copied. Returns the store
path and the cryptographic hash of the contents of srcPath. */
std::pair<Path, Hash> computeStorePathForPath(const Path & srcPath,
bool recursive = true, HashType hashAlgo = htSHA256,
PathFilter & filter = defaultPathFilter) const;
std::pair<Path, Hash> computeStorePathForPath(const string & name,
const Path & srcPath, bool recursive = true,
HashType hashAlgo = htSHA256, PathFilter & filter = defaultPathFilter) const;
/* Preparatory part of addTextToStore().

1
tests/lang/data Normal file
View file

@ -0,0 +1 @@
foo

1
tests/lang/eval-okay-path.exp Normal file
View file

@ -0,0 +1 @@
"/run/user/1000/nix-test/store/wjagrv37lfvfx92g2gf3yqflwypj0q1y-output"

7
tests/lang/eval-okay-path.nix Normal file
View file

@ -0,0 +1,7 @@
builtins.path
{ path = ./.;
filter = path: _: baseNameOf path == "data";
recursive = true;
sha256 = "1yhm3gwvg5a41yylymgblsclk95fs6jy72w0wv925mmidlhcq4sw";
name = "output";
}