refactor(3p/nix/libexpr): Make nix::AttrName a std::variant

nix:AttrName was one of the few classes that relied on the default
constructor of nix::Symbol (which I am trying to remove in a separate
change).

The class essentially represents the name of an attribute in a set,
which is either just a string expression or a dynamically evaluated
expression (e.g. string interpolation).

Previously it would be constructed by only setting one of the fields
and defaulting the other, now it is an explicit std::variant.

Note that there are several code paths where not all eventualities are
handled and this code is bug-for-bug compatible with those, except
that unknown conditions (which should never work) are now throwing
instead of silently doing ... something.

The language tests pass with this change, and the depot derivations
that I tested with evaluated successfully.

Change-Id: Icf1ee60a5f8308f4ab18a82749e00cf37a938a8f
Reviewed-on: https://cl.tvl.fyi/c/depot/+/1138
Reviewed-by: edef <edef@edef.eu>
Reviewed-by: glittershark <grfn@gws.fyi>
Tested-by: BuildkiteCI
This commit is contained in:
Vincent Ambo 2020-07-13 20:52:35 +01:00 committed by tazjin
parent 693661fe87
commit f3165f48aa
7 changed files with 67 additions and 53 deletions

View file

@ -6,6 +6,7 @@
#include <fstream> #include <fstream>
#include <iostream> #include <iostream>
#include <new> #include <new>
#include <variant>
#include <absl/strings/match.h> #include <absl/strings/match.h>
#include <gc/gc.h> #include <gc/gc.h>
@ -24,6 +25,7 @@
#include "libutil/hash.hh" #include "libutil/hash.hh"
#include "libutil/json.hh" #include "libutil/json.hh"
#include "libutil/util.hh" #include "libutil/util.hh"
#include "libutil/visitor.hh"
namespace nix { namespace nix {
@ -185,13 +187,15 @@ static void* oomHandler(size_t requested) {
#endif #endif
static Symbol getName(const AttrName& name, EvalState& state, Env& env) { static Symbol getName(const AttrName& name, EvalState& state, Env& env) {
if (name.symbol.set()) { return std::visit(
return name.symbol; util::overloaded{[&](const Symbol& name) -> Symbol { return name; },
} [&](Expr* expr) -> Symbol {
Value nameValue; Value nameValue;
name.expr->eval(state, env, nameValue); expr->eval(state, env, nameValue);
state.forceStringNoCtx(nameValue); state.forceStringNoCtx(nameValue);
return state.symbols.Create(nameValue.string.s); return state.symbols.Create(nameValue.string.s);
}},
name);
} }
static bool gcInitialised = false; static bool gcInitialised = false;
@ -890,12 +894,7 @@ static std::string showAttrPath(EvalState& state, Env& env,
} else { } else {
first = false; first = false;
} }
try { out << getName(i, state, env);
out << getName(i, state, env);
} catch (Error& e) {
assert(!i.symbol.set());
out << "\"${" << *i.expr << "}\"";
}
} }
return out.str(); return out.str();
} }

View file

@ -1,9 +1,11 @@
#include "libexpr/nixexpr.hh" #include "libexpr/nixexpr.hh"
#include <cstdlib> #include <cstdlib>
#include <variant>
#include "libstore/derivations.hh" #include "libstore/derivations.hh"
#include "libutil/util.hh" #include "libutil/util.hh"
#include "libutil/visitor.hh"
namespace nix { namespace nix {
@ -198,17 +200,17 @@ std::ostream& operator<<(std::ostream& str, const Pos& pos) {
std::string showAttrPath(const AttrPath& attrPath) { std::string showAttrPath(const AttrPath& attrPath) {
std::ostringstream out; std::ostringstream out;
bool first = true; bool first = true;
for (auto& i : attrPath) { for (auto& attr : attrPath) {
if (!first) { if (!first) {
out << '.'; out << '.';
} else { } else {
first = false; first = false;
} }
if (i.symbol.set()) {
out << i.symbol; std::visit(util::overloaded{
} else { [&](const Symbol& sym) { out << sym; },
out << "\"${" << *i.expr << "}\""; [&](const Expr* expr) { out << "\"${" << *expr << "}\""; }},
} attr);
} }
return out.str(); return out.str();
} }
@ -268,8 +270,8 @@ void ExprSelect::bindVars(const StaticEnv& env) {
def->bindVars(env); def->bindVars(env);
} }
for (auto& i : attrPath) { for (auto& i : attrPath) {
if (!i.symbol.set()) { if (auto* expr = std::get_if<Expr*>(&i)) {
i.expr->bindVars(env); (*expr)->bindVars(env);
} }
} }
} }
@ -277,8 +279,8 @@ void ExprSelect::bindVars(const StaticEnv& env) {
void ExprOpHasAttr::bindVars(const StaticEnv& env) { void ExprOpHasAttr::bindVars(const StaticEnv& env) {
e->bindVars(env); e->bindVars(env);
for (auto& i : attrPath) { for (auto& i : attrPath) {
if (!i.symbol.set()) { if (auto* expr = std::get_if<Expr*>(&i)) {
i.expr->bindVars(env); (*expr)->bindVars(env);
} }
} }
} }

View file

@ -1,6 +1,7 @@
#pragma once #pragma once
#include <map> #include <map>
#include <variant>
#include "libexpr/symbol-table.hh" #include "libexpr/symbol-table.hh"
#include "libexpr/value.hh" #include "libexpr/value.hh"
@ -60,12 +61,7 @@ class EvalState;
struct StaticEnv; struct StaticEnv;
/* An attribute path is a sequence of attribute names. */ /* An attribute path is a sequence of attribute names. */
struct AttrName { using AttrName = std::variant<Symbol, Expr*>;
Symbol symbol;
Expr* expr;
AttrName(const Symbol& s) : symbol(s){};
AttrName(Expr* e) : expr(e){};
};
typedef std::vector<AttrName> AttrPath; typedef std::vector<AttrName> AttrPath;

View file

@ -16,6 +16,7 @@
#ifndef BISON_HEADER #ifndef BISON_HEADER
#define BISON_HEADER #define BISON_HEADER
#include <variant>
#include "libutil/util.hh" #include "libutil/util.hh"
#include "libexpr/nixexpr.hh" #include "libexpr/nixexpr.hh"
#include "libexpr/eval.hh" #include "libexpr/eval.hh"
@ -84,30 +85,39 @@ static void addAttr(ExprAttrs * attrs, AttrPath & attrPath,
// Checking attrPath validity. // Checking attrPath validity.
// =========================== // ===========================
for (i = attrPath.begin(); i + 1 < attrPath.end(); i++) { for (i = attrPath.begin(); i + 1 < attrPath.end(); i++) {
if (i->symbol.set()) { if (const auto* sym = std::get_if<Symbol>(&(*i)); sym && sym->set()) {
ExprAttrs::AttrDefs::iterator j = attrs->attrs.find(i->symbol); ExprAttrs::AttrDefs::iterator j = attrs->attrs.find(*sym);
if (j != attrs->attrs.end()) { if (j != attrs->attrs.end()) {
if (!j->second.inherited) { if (!j->second.inherited) {
ExprAttrs * attrs2 = dynamic_cast<ExprAttrs *>(j->second.e); ExprAttrs * attrs2 = dynamic_cast<ExprAttrs *>(j->second.e);
if (!attrs2) { dupAttr(attrPath, pos, j->second.pos); } if (!attrs2) { dupAttr(attrPath, pos, j->second.pos); }
attrs = attrs2; attrs = attrs2;
} else } else {
dupAttr(attrPath, pos, j->second.pos); dupAttr(attrPath, pos, j->second.pos);
}
} else { } else {
ExprAttrs * nested = new ExprAttrs; ExprAttrs* nested = new ExprAttrs;
attrs->attrs[i->symbol] = ExprAttrs::AttrDef(nested, pos); attrs->attrs[*sym] = ExprAttrs::AttrDef(nested, pos);
attrs = nested; attrs = nested;
} }
} else { } else {
ExprAttrs *nested = new ExprAttrs; // Yes, this code does not handle all conditions
attrs->dynamicAttrs.push_back(ExprAttrs::DynamicAttrDef(i->expr, nested, pos)); // exhaustively. We use std::get to throw if the condition
attrs = nested; // that isn't covered happens, which is potentially a
// behaviour change from the previous default constructed
// Symbol. It should alert us about anything untoward going
// on here.
auto* expr = std::get<Expr*>(*i);
ExprAttrs *nested = new ExprAttrs;
attrs->dynamicAttrs.push_back(ExprAttrs::DynamicAttrDef(expr, nested, pos));
attrs = nested;
} }
} }
// Expr insertion. // Expr insertion.
// ========================== // ==========================
if (i->symbol.set()) { if (auto* sym = std::get_if<Symbol>(&(*i)); sym && sym->set()) {
ExprAttrs::AttrDefs::iterator j = attrs->attrs.find(i->symbol); ExprAttrs::AttrDefs::iterator j = attrs->attrs.find(*sym);
if (j != attrs->attrs.end()) { if (j != attrs->attrs.end()) {
// This attr path is already defined. However, if both // This attr path is already defined. However, if both
// e and the expr pointed by the attr path are two attribute sets, // e and the expr pointed by the attr path are two attribute sets,
@ -118,8 +128,9 @@ static void addAttr(ExprAttrs * attrs, AttrPath & attrPath,
if (jAttrs && ae) { if (jAttrs && ae) {
for (auto & ad : ae->attrs) { for (auto & ad : ae->attrs) {
auto j2 = jAttrs->attrs.find(ad.first); auto j2 = jAttrs->attrs.find(ad.first);
if (j2 != jAttrs->attrs.end()) // Attr already defined in iAttrs, error. if (j2 != jAttrs->attrs.end()) {// Attr already defined in iAttrs, error.
dupAttr(ad.first, j2->second.pos, ad.second.pos); dupAttr(ad.first, j2->second.pos, ad.second.pos);
}
jAttrs->attrs[ad.first] = ad.second; jAttrs->attrs[ad.first] = ad.second;
} }
} else { } else {
@ -127,11 +138,13 @@ static void addAttr(ExprAttrs * attrs, AttrPath & attrPath,
} }
} else { } else {
// This attr path is not defined. Let's create it. // This attr path is not defined. Let's create it.
attrs->attrs[i->symbol] = ExprAttrs::AttrDef(e, pos); attrs->attrs[*sym] = ExprAttrs::AttrDef(e, pos);
e->setName(i->symbol); e->setName(*sym);
} }
} else { } else {
attrs->dynamicAttrs.push_back(ExprAttrs::DynamicAttrDef(i->expr, e, pos)); // Same caveat as the identical line above.
auto* expr = std::get<Expr*>(*i);
attrs->dynamicAttrs.push_back(ExprAttrs::DynamicAttrDef(expr, e, pos));
} }
} }
@ -444,19 +457,23 @@ binds
| binds INHERIT attrs ';' | binds INHERIT attrs ';'
{ $$ = $1; { $$ = $1;
for (auto & i : *$3) { for (auto & i : *$3) {
if ($$->attrs.find(i.symbol) != $$->attrs.end()) auto sym = std::get<Symbol>(i);
dupAttr(i.symbol, makeCurPos(@3, data), $$->attrs[i.symbol].pos); if ($$->attrs.find(sym) != $$->attrs.end()) {
dupAttr(sym, makeCurPos(@3, data), $$->attrs[sym].pos);
}
Pos pos = makeCurPos(@3, data); Pos pos = makeCurPos(@3, data);
$$->attrs[i.symbol] = ExprAttrs::AttrDef(new ExprVar(CUR_POS, i.symbol), pos, true); $$->attrs[sym] = ExprAttrs::AttrDef(new ExprVar(CUR_POS, sym), pos, true);
} }
} }
| binds INHERIT '(' expr ')' attrs ';' | binds INHERIT '(' expr ')' attrs ';'
{ $$ = $1; { $$ = $1;
/* !!! Should ensure sharing of the expression in $4. */ /* !!! Should ensure sharing of the expression in $4. */
for (auto & i : *$6) { for (auto & i : *$6) {
if ($$->attrs.find(i.symbol) != $$->attrs.end()) auto sym = std::get<Symbol>(i);
dupAttr(i.symbol, makeCurPos(@6, data), $$->attrs[i.symbol].pos); if ($$->attrs.find(sym) != $$->attrs.end()) {
$$->attrs[i.symbol] = ExprAttrs::AttrDef(new ExprSelect(CUR_POS, $4, i.symbol), makeCurPos(@6, data)); dupAttr(sym, makeCurPos(@6, data), $$->attrs[sym].pos);
}
$$->attrs[sym] = ExprAttrs::AttrDef(new ExprSelect(CUR_POS, $4, sym), makeCurPos(@6, data));
} }
} }
| { $$ = new ExprAttrs; } | { $$ = new ExprAttrs; }

View file

@ -21,7 +21,7 @@ class Symbol {
bool operator<(const Symbol& s2) const { return *s < *s2.s; } bool operator<(const Symbol& s2) const { return *s < *s2.s; }
operator const std::string&() const { return *s; } operator const std::string &() const { return *s; }
bool set() const { return s; } bool set() const { return s; }

View file

@ -102,8 +102,8 @@ void AbstractConfig::applyConfigFile(const Path& path) {
} }
// TODO(tazjin): absl::string_view after path functions are fixed. // TODO(tazjin): absl::string_view after path functions are fixed.
std::vector<std::string> tokens = std::vector<std::string> tokens = absl::StrSplit(
absl::StrSplit(line, absl::ByAnyChar(" \t\n\r"), absl::SkipWhitespace()); line, absl::ByAnyChar(" \t\n\r"), absl::SkipWhitespace());
if (tokens.empty()) { if (tokens.empty()) {
continue; continue;
} }

View file

@ -16,6 +16,7 @@
#include <unistd.h> #include <unistd.h>
#include "libmain/shared.hh" #include "libmain/shared.hh"
#include "libproto/worker.pb.h"
#include "libstore/derivations.hh" #include "libstore/derivations.hh"
#include "libstore/globals.hh" #include "libstore/globals.hh"
#include "libstore/local-store.hh" #include "libstore/local-store.hh"
@ -27,7 +28,6 @@
#include "libutil/serialise.hh" #include "libutil/serialise.hh"
#include "libutil/util.hh" #include "libutil/util.hh"
#include "nix/legacy.hh" #include "nix/legacy.hh"
#include "libproto/worker.pb.h"
using namespace nix; using namespace nix;