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Add support for passing structured data to builders

Previously, all derivation attributes had to be coerced into strings
so that they could be passed via the environment. This is lossy
(e.g. lists get flattened, necessitating configureFlags
vs. configureFlagsArray, of which the latter cannot be specified as an
attribute), doesn't support attribute sets at all, and has size
limitations (necessitating hacks like passAsFile).

This patch adds a new mode for passing attributes to builders, namely
encoded as a JSON file ".attrs.json" in the current directory of the
builder. This mode is activated via the special attribute

  __structuredAttrs = true;

(The idea is that one day we can set this in stdenv.mkDerivation.)

For example,

  stdenv.mkDerivation {
    __structuredAttrs = true;
    name = "foo";
    buildInputs = [ pkgs.hello pkgs.cowsay ];
    doCheck = true;
    hardening.format = false;
  }

results in a ".attrs.json" file containing (sans the indentation):

  {
    "buildInputs": [],
    "builder": "/nix/store/ygl61ycpr2vjqrx775l1r2mw1g2rb754-bash-4.3-p48/bin/bash",
    "configureFlags": [
      "--with-foo",
      "--with-bar=1 2"
    ],
    "doCheck": true,
    "hardening": {
      "format": false
    },
    "name": "foo",
    "nativeBuildInputs": [
      "/nix/store/10h6li26i7g6z3mdpvra09yyf10mmzdr-hello-2.10",
      "/nix/store/4jnvjin0r6wp6cv1hdm5jbkx3vinlcvk-cowsay-3.03"
    ],
    "propagatedBuildInputs": [],
    "propagatedNativeBuildInputs": [],
    "stdenv": "/nix/store/f3hw3p8armnzy6xhd4h8s7anfjrs15n2-stdenv",
    "system": "x86_64-linux"
  }

"passAsFile" is ignored in this mode because it's not needed - large
strings are included directly in the JSON representation.

It is up to the builder to do something with the JSON
representation. For example, in bash-based builders, lists/attrsets of
string values could be mapped to bash (associative) arrays.
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edolstra committed Jan 25, 2017
1 parent 54801ed commit 6de33a9c675b187437a2e1abbcb290981a89ecb1
Showing with 130 additions and 58 deletions.
  1. +2 −0 src/libexpr/eval.cc
  2. +1 −1 src/libexpr/eval.hh
  3. +88 −39 src/libexpr/primops.cc
  4. +39 −18 src/libstore/build.cc
@@ -291,6 +291,8 @@ EvalState::EvalState(const Strings & _searchPath, ref<Store> store)
, sToString(symbols.create("__toString"))
, sRight(symbols.create("right"))
, sWrong(symbols.create("wrong"))
, sStructuredAttrs(symbols.create("__structuredAttrs"))
, sBuilder(symbols.create("builder"))
, store(store)
, baseEnv(allocEnv(128))
, staticBaseEnv(false, 0)
@@ -68,7 +68,7 @@ public:
const Symbol sWith, sOutPath, sDrvPath, sType, sMeta, sName, sValue,
sSystem, sOverrides, sOutputs, sOutputName, sIgnoreNulls,
sFile, sLine, sColumn, sFunctor, sToString,
sRight, sWrong;
sRight, sWrong, sStructuredAttrs, sBuilder;
Symbol sDerivationNix;
/* If set, force copying files to the Nix store even if they
@@ -8,6 +8,7 @@
#include "names.hh"
#include "store-api.hh"
#include "util.hh"
#include "json.hh"
#include "value-to-json.hh"
#include "value-to-xml.hh"
#include "primops.hh"
@@ -474,6 +475,13 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
throw;
}
/* Check whether attributes should be passed as a JSON file. */
std::ostringstream jsonBuf;
std::unique_ptr<JSONObject> jsonObject;
attr = args[0]->attrs->find(state.sStructuredAttrs);
if (attr != args[0]->attrs->end() && state.forceBool(*attr->value, pos))
jsonObject = std::make_unique<JSONObject>(jsonBuf);
/* Check whether null attributes should be ignored. */
bool ignoreNulls = false;
attr = args[0]->attrs->find(state.sIgnoreNulls);
@@ -491,64 +499,100 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
StringSet outputs;
outputs.insert("out");
for (auto & i : *args[0]->attrs) {
if (i.name == state.sIgnoreNulls) continue;
string key = i.name;
for (auto & i : args[0]->attrs->lexicographicOrder()) {
if (i->name == state.sIgnoreNulls) continue;
string key = i->name;
Activity act(*logger, lvlVomit, format("processing attribute ‘%1%’") % key);
auto handleHashMode = [&](const std::string & s) {
if (s == "recursive") outputHashRecursive = true;
else if (s == "flat") outputHashRecursive = false;
else throw EvalError("invalid value ‘%s’ for ‘outputHashMode’ attribute, at %s", s, posDrvName);
};
auto handleOutputs = [&](const Strings & ss) {
outputs.clear();
for (auto & j : ss) {
if (outputs.find(j) != outputs.end())
throw EvalError(format("duplicate derivation output ‘%1%’, at %2%") % j % posDrvName);
/* !!! Check whether j is a valid attribute
name. */
/* Derivations cannot be named ‘drv’, because
then we'd have an attribute ‘drvPath’ in
the resulting set. */
if (j == "drv")
throw EvalError(format("invalid derivation output name ‘drv’, at %1%") % posDrvName);
outputs.insert(j);
}
if (outputs.empty())
throw EvalError(format("derivation cannot have an empty set of outputs, at %1%") % posDrvName);
};
try {
if (ignoreNulls) {
state.forceValue(*i.value);
if (i.value->type == tNull) continue;
state.forceValue(*i->value);
if (i->value->type == tNull) continue;
}
/* The `args' attribute is special: it supplies the
command-line arguments to the builder. */
if (key == "args") {
state.forceList(*i.value, pos);
for (unsigned int n = 0; n < i.value->listSize(); ++n) {
string s = state.coerceToString(posDrvName, *i.value->listElems()[n], context, true);
state.forceList(*i->value, pos);
for (unsigned int n = 0; n < i->value->listSize(); ++n) {
string s = state.coerceToString(posDrvName, *i->value->listElems()[n], context, true);
drv.args.push_back(s);
}
}
/* All other attributes are passed to the builder through
the environment. */
else {
string s = state.coerceToString(posDrvName, *i.value, context, true);
drv.env[key] = s;
if (key == "builder") drv.builder = s;
else if (i.name == state.sSystem) drv.platform = s;
else if (i.name == state.sName) {
drvName = s;
printMsg(lvlVomit, format("derivation name is ‘%1%’") % drvName);
}
else if (key == "outputHash") outputHash = s;
else if (key == "outputHashAlgo") outputHashAlgo = s;
else if (key == "outputHashMode") {
if (s == "recursive") outputHashRecursive = true;
else if (s == "flat") outputHashRecursive = false;
else throw EvalError(format("invalid value ‘%1%’ for ‘outputHashMode’ attribute, at %2%") % s % posDrvName);
}
else if (key == "outputs") {
Strings tmp = tokenizeString<Strings>(s);
outputs.clear();
for (auto & j : tmp) {
if (outputs.find(j) != outputs.end())
throw EvalError(format("duplicate derivation output ‘%1%’, at %2%") % j % posDrvName);
/* !!! Check whether j is a valid attribute
name. */
/* Derivations cannot be named ‘drv’, because
then we'd have an attribute ‘drvPath’ in
the resulting set. */
if (j == "drv")
throw EvalError(format("invalid derivation output name ‘drv’, at %1%") % posDrvName);
outputs.insert(j);
if (jsonObject) {
if (i->name == state.sStructuredAttrs) continue;
auto placeholder(jsonObject->placeholder(key));
printValueAsJSON(state, true, *i->value, placeholder, context);
if (i->name == state.sBuilder)
drv.builder = state.forceString(*i->value, context, posDrvName);
else if (i->name == state.sSystem)
drv.platform = state.forceStringNoCtx(*i->value, posDrvName);
else if (i->name == state.sName)
drvName = state.forceStringNoCtx(*i->value, posDrvName);
else if (key == "outputHash")
outputHash = state.forceStringNoCtx(*i->value, posDrvName);
else if (key == "outputHashAlgo")
outputHashAlgo = state.forceStringNoCtx(*i->value, posDrvName);
else if (key == "outputHashMode")
handleHashMode(state.forceStringNoCtx(*i->value, posDrvName));
else if (key == "outputs") {
/* Require ‘outputs’ to be a list of strings. */
state.forceList(*i->value, posDrvName);
Strings ss;
for (unsigned int n = 0; n < i->value->listSize(); ++n)
ss.emplace_back(state.forceStringNoCtx(*i->value->listElems()[n], posDrvName));
handleOutputs(ss);
}
} else {
auto s = state.coerceToString(posDrvName, *i->value, context, true);
drv.env.emplace(key, s);
if (i->name == state.sBuilder) drv.builder = s;
else if (i->name == state.sSystem) drv.platform = s;
else if (i->name == state.sName) {
drvName = s;
printMsg(lvlVomit, format("derivation name is ‘%1%’") % drvName);
}
if (outputs.empty())
throw EvalError(format("derivation cannot have an empty set of outputs, at %1%") % posDrvName);
else if (key == "outputHash") outputHash = s;
else if (key == "outputHashAlgo") outputHashAlgo = s;
else if (key == "outputHashMode") handleHashMode(s);
else if (key == "outputs")
handleOutputs(tokenizeString<Strings>(s));
}
}
} catch (Error & e) {
@@ -558,6 +602,11 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
}
}
if (jsonObject) {
jsonObject.reset();
drv.env.emplace("__json", jsonBuf.str());
}
/* Everything in the context of the strings in the derivation
attributes should be added as dependencies of the resulting
derivation. */
@@ -865,6 +865,9 @@ class DerivationGoal : public Goal
/* Fill in the environment for the builder. */
void initEnv();
/* Write a JSON file containing the derivation attributes. */
void writeStructuredAttrs();
/* Make a file owned by the builder. */
void chownToBuilder(const Path & path);
@@ -1726,13 +1729,15 @@ void DerivationGoal::startBuilder()
tmpDirInSandbox = useChroot ? canonPath("/tmp", true) + "/nix-build-" + drvName + "-0" : tmpDir;
chownToBuilder(tmpDir);
/* Construct the environment passed to the builder. */
initEnv();
/* Substitute output placeholders with the actual output paths. */
for (auto & output : drv->outputs)
inputRewrites[hashPlaceholder(output.first)] = output.second.path;
/* Construct the environment passed to the builder. */
initEnv();
writeStructuredAttrs();
/* Handle exportReferencesGraph(), if set. */
doExportReferencesGraph();
@@ -2148,22 +2153,29 @@ void DerivationGoal::initEnv()
/* The maximum number of cores to utilize for parallel building. */
env["NIX_BUILD_CORES"] = (format("%d") % settings.buildCores).str();
/* Add all bindings specified in the derivation via the
environments, except those listed in the passAsFile
attribute. Those are passed as file names pointing to
temporary files containing the contents. */
StringSet passAsFile = tokenizeString<StringSet>(get(drv->env, "passAsFile"));
int fileNr = 0;
for (auto & i : drv->env) {
if (passAsFile.find(i.first) == passAsFile.end()) {
env[i.first] = i.second;
} else {
string fn = ".attr-" + std::to_string(fileNr++);
Path p = tmpDir + "/" + fn;
writeFile(p, i.second);
chownToBuilder(p);
env[i.first + "Path"] = tmpDirInSandbox + "/" + fn;
/* In non-structured mode, add all bindings specified in the
derivation via the environments, except those listed in the
passAsFile attribute. Those are passed as file names pointing
to temporary files containing the contents. Note that
passAsFile is ignored in structure mode because it's not
needed (attributes are not passed through the environment, so
there is no size constraint). */
if (!drv->env.count("__json")) {
StringSet passAsFile = tokenizeString<StringSet>(get(drv->env, "passAsFile"));
int fileNr = 0;
for (auto & i : drv->env) {
if (passAsFile.find(i.first) == passAsFile.end()) {
env[i.first] = i.second;
} else {
string fn = ".attr-" + std::to_string(fileNr++);
Path p = tmpDir + "/" + fn;
writeFile(p, i.second);
chownToBuilder(p);
env[i.first + "Path"] = tmpDirInSandbox + "/" + fn;
}
}
}
/* For convenience, set an environment pointing to the top build
@@ -2201,6 +2213,15 @@ void DerivationGoal::initEnv()
}
void DerivationGoal::writeStructuredAttrs()
{
auto json = drv->env.find("__json");
if (json == drv->env.end()) return;
writeFile(tmpDir + "/.attrs.json", rewriteStrings(json->second, inputRewrites));
}
void DerivationGoal::chownToBuilder(const Path & path)
{
if (!buildUser) return;

2 comments on commit 6de33a9

@copumpkin

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copumpkin replied Jan 27, 2017

Very cool 👍

@domenkozar

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domenkozar replied Feb 3, 2017

cc @Gabriel439 for Dhall

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