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libexpr: refactor string coercion modes

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Inspired by cl/3191 and
https://git.lix.systems/delroth/lix/commit/ae0247cbb4fc739ab013dc87d02e5f3191cf25ab.

`coerceToString` takes now an enumeration that lives in `value.hh`, this
enumeration is meant to represent increasing subsets of behaviors, e.g.
any level above Strict should do what the previous levels do and extra
behavior until `ToString`, which transforms many Nix values into an
arbitrary string representation, e.g. `null` to `""`.

Change-Id: Ief7a4756e8c0660e197623efebeaf07710746ec7
Signed-off-by: Raito Bezarius <raito@lix.systems>
Co-authored-by: Pierre Bourdon <delroth@gmail.com>
This commit is contained in:
Raito Bezarius
2025-05-20 19:14:49 +02:00
co-authored by Pierre Bourdon
parent eb18a90afb
commit dab871f129
9 changed files with 50 additions and 33 deletions
Download Patch File Download Diff File Expand all files Collapse all files
lix/libexpr/eval.cc
+12 -12
View File
@@ -2033,7 +2033,7 @@ void ExprConcatStrings::eval(EvalState & state, Env & env, Value & v)
path */
auto part = state.coerceToString(i_pos, vTmp, context,
"while evaluating a path segment",
false, firstType == nString, !first);
StringCoercionMode::Strict, firstType == nString, !first);
sSize += part->size();
s.emplace_back(std::move(part));
}
@@ -2266,7 +2266,7 @@ bool EvalState::isDerivation(Value & v)
std::optional<std::string> EvalState::tryAttrsToString(const PosIdx pos, Value & v,
NixStringContext & context, bool coerceMore, bool copyToStore)
NixStringContext & context, StringCoercionMode mode, bool copyToStore)
{
auto i = v.attrs->find(ctx.s.toString);
if (i != v.attrs->end()) {
@@ -2275,7 +2275,7 @@ std::optional<std::string> EvalState::tryAttrsToString(const PosIdx pos, Value &
callFunction(*i->value, v, v1, i->pos);
return coerceToString(pos, v1, context,
"while evaluating the result of the `__toString` attribute",
coerceMore, copyToStore).toOwned();
mode, copyToStore).toOwned();
} catch (EvalError & e) {
e.addTrace(ctx.positions[pos], "while converting a set to string");
throw;
@@ -2290,7 +2290,7 @@ BackedStringView EvalState::coerceToString(
Value & v,
NixStringContext & context,
std::string_view errorCtx,
bool coerceMore,
StringCoercionMode mode,
bool copyToStore,
bool canonicalizePath)
{
@@ -2314,7 +2314,7 @@ BackedStringView EvalState::coerceToString(
}
if (v.type() == nAttrs) {
auto maybeString = tryAttrsToString(pos, v, context, coerceMore, copyToStore);
auto maybeString = tryAttrsToString(pos, v, context, mode, copyToStore);
if (maybeString)
return std::move(*maybeString);
auto i = v.attrs->find(ctx.s.outPath);
@@ -2328,19 +2328,19 @@ BackedStringView EvalState::coerceToString(
.debugThrow();
}
return coerceToString(pos, *i->value, context, errorCtx,
coerceMore, copyToStore, canonicalizePath);
mode, copyToStore, canonicalizePath);
}
if (v.type() == nExternal) {
try {
return v.external->coerceToString(*this, pos, context, coerceMore, copyToStore);
return v.external->coerceToString(*this, pos, context, mode, copyToStore);
} catch (Error & e) {
e.addTrace(nullptr, errorCtx);
throw;
}
}
if (coerceMore) {
if (mode >= StringCoercionMode::ToString) {
/* Note that `false' is represented as an empty string for
shell scripting convenience, just like `null'. */
if (v.type() == nBool && v.boolean) return "1";
@@ -2355,7 +2355,7 @@ BackedStringView EvalState::coerceToString(
try {
result += *coerceToString(pos, *v2, context,
"while evaluating one element of the list",
coerceMore, copyToStore, canonicalizePath);
mode, copyToStore, canonicalizePath);
} catch (Error & e) {
e.addTrace(ctx.positions[pos], errorCtx);
throw;
@@ -2412,7 +2412,7 @@ try {
SourcePath EvalState::coerceToPath(const PosIdx pos, Value & v, NixStringContext & context, std::string_view errorCtx)
{
auto path = coerceToString(pos, v, context, errorCtx, false, false, true).toOwned();
auto path = coerceToString(pos, v, context, errorCtx, StringCoercionMode::Strict, false, true).toOwned();
if (path == "" || path[0] != '/')
ctx.errors.make<EvalError>("string '%1%' doesn't represent an absolute path", path).withTrace(pos, errorCtx).debugThrow();
return CanonPath(path);
@@ -2421,7 +2421,7 @@ SourcePath EvalState::coerceToPath(const PosIdx pos, Value & v, NixStringContext
StorePath EvalState::coerceToStorePath(const PosIdx pos, Value & v, NixStringContext & context, std::string_view errorCtx)
{
auto path = coerceToString(pos, v, context, errorCtx, false, false, true).toOwned();
auto path = coerceToString(pos, v, context, errorCtx, StringCoercionMode::Strict, false, true).toOwned();
if (auto storePath = ctx.store->maybeParseStorePath(path))
return *storePath;
ctx.errors.make<EvalError>("path '%1%' is not in the Nix store", path).withTrace(pos, errorCtx).debugThrow();
@@ -2883,7 +2883,7 @@ try {
}
std::string ExternalValueBase::coerceToString(EvalState & state, const PosIdx & pos, NixStringContext & context, bool copyMore, bool copyToStore) const
std::string ExternalValueBase::coerceToString(EvalState & state, const PosIdx & pos, NixStringContext & context, StringCoercionMode mode, bool copyToStore) const
{
state.ctx.errors.make<TypeError>(
"cannot coerce %1% to a string: %2%", showType(), *this
lix/libexpr/eval.hh
+3 -4
View File
@@ -767,19 +767,18 @@ public:
bool isDerivation(Value & v);
std::optional<std::string> tryAttrsToString(const PosIdx pos, Value & v,
NixStringContext & context, bool coerceMore = false, bool copyToStore = true);
NixStringContext & context, StringCoercionMode mode = StringCoercionMode::Strict, bool copyToStore = true);
/**
* String coercion.
*
* Converts strings, paths and derivations to a
* string. If `coerceMore` is set, also converts nulls, integers,
* booleans and lists to a string. If `copyToStore` is set,
* string. If `copyToStore` is set,
* referenced paths are copied to the Nix store as a side effect.
*/
BackedStringView coerceToString(const PosIdx pos, Value & v, NixStringContext & context,
std::string_view errorCtx,
bool coerceMore = false, bool copyToStore = true,
StringCoercionMode mode = StringCoercionMode::Strict, bool copyToStore = true,
bool canonicalizePath = true);
/**
lix/libexpr/flake/flake.cc
+1 -1
View File
@@ -298,7 +298,7 @@ static Flake getFlake(
NixStringContext emptyContext = {};
flake.config.settings.emplace(
state.ctx.symbols[setting.name],
state.coerceToString(setting.pos, *setting.value, emptyContext, "", false, true, true) .toOwned());
state.coerceToString(setting.pos, *setting.value, emptyContext, "", StringCoercionMode::Strict, true, true) .toOwned());
}
else if (setting.value->type() == nInt)
flake.config.settings.emplace(
lix/libexpr/primops.cc
+9 -9
View File
@@ -315,13 +315,13 @@ void prim_exec(EvalState & state, Value * * args, Value & v)
NixStringContext context;
auto program = state.coerceToString(noPos, *elems[0], context,
"while evaluating the first element of the argument passed to builtins.exec",
false, false).toOwned();
StringCoercionMode::Strict, false).toOwned();
Strings commandArgs;
for (unsigned int i = 1; i < args[0]->listSize(); ++i) {
commandArgs.push_back(
state.coerceToString(noPos, *elems[i], context,
"while evaluating an element of the argument passed to builtins.exec",
false, false).toOwned());
StringCoercionMode::Strict, false).toOwned());
}
try {
auto _ = state.realiseContext(context); // FIXME: Handle CA derivations
@@ -610,7 +610,7 @@ static void prim_addErrorContext(EvalState & state, Value * * args, Value & v)
NixStringContext context;
auto message = state.coerceToString(noPos, *args[0], context,
"while evaluating the error message passed to builtins.addErrorContext",
false, false).toOwned();
StringCoercionMode::Strict, false).toOwned();
e.addTrace(nullptr, HintFmt(message));
throw;
}
@@ -880,7 +880,7 @@ drvName, Bindings * attrs, Value & v)
for (auto elem : i->value->listItems()) {
auto s = state.coerceToString(noPos, *elem, context,
"while evaluating an element of the argument list",
true).toOwned();
StringCoercionMode::ToString).toOwned();
drv.args.push_back(s);
}
}
@@ -929,7 +929,7 @@ drvName, Bindings * attrs, Value & v)
} else {
auto s = state.coerceToString(noPos, *i->value, context, context_below, true).toOwned();
auto s = state.coerceToString(noPos, *i->value, context, context_below, StringCoercionMode::ToString).toOwned();
drv.env.emplace(key, s);
if (i->name == state.ctx.s.builder) drv.builder = std::move(s);
else if (i->name == state.ctx.s.system) drv.platform = std::move(s);
@@ -1212,7 +1212,7 @@ static void prim_baseNameOf(EvalState & state, Value * * args, Value & v)
NixStringContext context;
v.mkString(baseNameOf(*state.coerceToString(noPos, *args[0], context,
"while evaluating the first argument passed to builtins.baseNameOf",
false, false)), context);
StringCoercionMode::Strict, false)), context);
}
/* Return the directory of the given path, i.e., everything before the
@@ -1228,7 +1228,7 @@ static void prim_dirOf(EvalState & state, Value * * args, Value & v)
NixStringContext context;
auto path = state.coerceToString(noPos, *args[0], context,
"while evaluating the first argument passed to 'builtins.dirOf'",
false, false);
StringCoercionMode::Strict, false);
auto dir = dirOf(*path);
v.mkString(dir, context);
}
@@ -1289,7 +1289,7 @@ static void prim_findFile(EvalState & state, Value * * args, Value & v)
NixStringContext context;
auto path = state.coerceToString(noPos, *i->value, context,
"while evaluating the `path` attribute of an element of the list passed to builtins.findFile",
false, false).toOwned();
StringCoercionMode::Strict, false).toOwned();
try {
auto rewrites = state.realiseContext(context);
@@ -2453,7 +2453,7 @@ static void prim_toString(EvalState & state, Value * * args, Value & v)
NixStringContext context;
auto s = state.coerceToString(noPos, *args[0], context,
"while evaluating the first argument passed to builtins.toString",
true, false);
StringCoercionMode::ToString, false);
v.mkString(*s, context);
}
lix/libexpr/primops/fetchMercurial.cc
+2 -2
View File
@@ -22,7 +22,7 @@ static void prim_fetchMercurial(EvalState & state, Value * * args, Value & v)
if (n == "url")
url = state.coerceToString(attr.pos, *attr.value, context,
"while evaluating the `url` attribute passed to builtins.fetchMercurial",
false, false).toOwned();
StringCoercionMode::Strict, false).toOwned();
else if (n == "rev") {
// Ugly: unlike fetchGit, here the "rev" attribute can
// be both a revision or a branch/tag name.
@@ -44,7 +44,7 @@ static void prim_fetchMercurial(EvalState & state, Value * * args, Value & v)
} else
url = state.coerceToString(noPos, *args[0], context,
"while evaluating the first argument passed to builtins.fetchMercurial",
false, false).toOwned();
StringCoercionMode::Strict, false).toOwned();
// FIXME: git externals probably can be used to bypass the URI
// whitelist. Ah well.
lix/libexpr/primops/fetchTree.cc
+2 -2
View File
@@ -139,7 +139,7 @@ static void fetchTree(
if (attr.name == state.ctx.s.type) 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();
auto s = state.coerceToString(attr.pos, *attr.value, context, "", StringCoercionMode::Strict, false).toOwned();
attrs.emplace(state.ctx.symbols[attr.name],
state.ctx.symbols[attr.name] == "url"
? type == "git"
@@ -173,7 +173,7 @@ static void fetchTree(
} else {
auto url = state.coerceToString(pos, *args[0], context,
"while evaluating the first argument passed to the fetcher",
false, false).toOwned();
StringCoercionMode::Strict, false).toOwned();
if (type == "git") {
fetchers::Attrs attrs;
lix/libexpr/value-to-json.cc
+1 -1
View File
@@ -46,7 +46,7 @@ JSON printValueAsJSON(EvalState & state, bool strict,
break;
case nAttrs: {
auto maybeString = state.tryAttrsToString(pos, v, context, false, false);
auto maybeString = state.tryAttrsToString(pos, v, context, StringCoercionMode::Strict, false);
if (maybeString) {
out = *maybeString;
break;
lix/libexpr/value.hh
+19 -1
View File
@@ -10,6 +10,7 @@
#include "lix/libexpr/gc-alloc.hh"
#include "lix/libexpr/symbol-table.hh"
#include "lix/libexpr/value/context.hh"
#include "lix/libutil/logging.hh"
#include "lix/libutil/source-path.hh"
#include "lix/libexpr/print-options.hh"
#include "lix/libutil/checked-arithmetic.hh"
@@ -59,6 +60,23 @@ typedef enum {
nExternal
} ValueType;
/**
* Modes of string coercion.
*
* Determines how permissive the coercion functions are when converting
* values to strings.
*
* - Strict: Only allow coercion of values that are already strings,
* paths, or derivations.
* - ToString: Additionally allow coercion of integers, booleans, null,
* and lists to strings.
*/
enum class StringCoercionMode {
Strict,
ToString,
};
class Bindings;
struct Env;
struct Expr;
@@ -106,7 +124,7 @@ class ExternalValueBase
* Coerce the value to a string. Defaults to uncoercable, i.e. throws an
* error.
*/
virtual std::string coerceToString(EvalState & state, const PosIdx & pos, NixStringContext & context, bool copyMore, bool copyToStore) const;
virtual std::string coerceToString(EvalState & state, const PosIdx & pos, NixStringContext & context, StringCoercionMode mode, bool copyToStore) const;
/**
* Compare to another value of the same type. Defaults to uncomparable,
subprojects/nix-eval-jobs/src/worker.cc
+1 -1
View File
@@ -94,7 +94,7 @@ readConstituents(const nix::Value *v, nix::box_ptr<nix::EvalState> &state,
nix::NixStringContext context;
state->coerceToString(a->pos, *a->value, context,
"while evaluating the `constituents` attribute",
true, false);
nix::StringCoercionMode::ToString, false);
for (auto &c : context)
std::visit(nix::overloaded{
[&](const nix::NixStringContextElem::Built &b) {