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Introduce AbstractPos

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This makes the position object used in exceptions abstract, with a
method getSource() to get the source code of the file in which the
error originated. This is needed for lazy trees because source files
don't necessarily exist in the filesystem, and we don't want to make
libutil depend on the InputAccessor type in libfetcher.
This commit is contained in:
Eelco Dolstra 2022-12-13 00:48:04 +01:00
parent edb54c62e6
commit b3fdab28a2
16 changed files with 231 additions and 279 deletions
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79
src/libexpr/nixexpr.cc
View file

@ -8,6 +8,65 @@
namespace nix {
struct SourcePathAdapter : AbstractPos
{
Path path;
SourcePathAdapter(Path path)
: path(std::move(path))
{
}
std::optional<std::string> getSource() const override
{
try {
return readFile(path);
} catch (Error &) {
return std::nullopt;
}
}
void print(std::ostream & out) const override
{
out << path;
}
};
struct StringPosAdapter : AbstractPos
{
void print(std::ostream & out) const override
{
out << "«string»";
}
};
struct StdinPosAdapter : AbstractPos
{
void print(std::ostream & out) const override
{
out << "«stdin»";
}
};
Pos::operator std::shared_ptr<AbstractPos>() const
{
std::shared_ptr<AbstractPos> pos;
if (auto path = std::get_if<Path>(&origin))
pos = std::make_shared<SourcePathAdapter>(*path);
else if (std::get_if<stdin_tag>(&origin))
pos = std::make_shared<StdinPosAdapter>();
else if (std::get_if<string_tag>(&origin))
pos = std::make_shared<StringPosAdapter>();
if (pos) {
pos->line = line;
pos->column = column;
}
return pos;
}
/* Displaying abstract syntax trees. */
static void showString(std::ostream & str, std::string_view s)
@ -248,24 +307,10 @@ void ExprPos::show(const SymbolTable & symbols, std::ostream & str) const
std::ostream & operator << (std::ostream & str, const Pos & pos)
{
if (!pos)
if (auto pos2 = (std::shared_ptr<AbstractPos>) pos) {
str << *pos2;
} else
str << "undefined position";
else
{
auto f = format(ANSI_BOLD "%1%" ANSI_NORMAL ":%2%:%3%");
switch (pos.origin) {
case foFile:
f % (const std::string &) pos.file;
break;
case foStdin:
case foString:
f % "(string)";
break;
default:
throw Error("unhandled Pos origin!");
}
str << (f % pos.line % pos.column).str();
}
return str;
}