lix/src/libexpr/nixexpr.cc
Eelco Dolstra 8d4268d190 Improve error formatting
Changes:

* The divider lines are gone. These were in practice a bit confusing,
  in particular with --show-trace or --keep-going, since then there
  were multiple lines, suggesting a start/end which wasn't the case.

* Instead, multi-line error messages are now indented to align with
  the prefix (e.g. "error: ").

* The 'description' field is gone since we weren't really using it.

* 'hint' is renamed to 'msg' since it really wasn't a hint.

* The error is now printed *before* the location info.

* The 'name' field is no longer printed since most of the time it
  wasn't very useful since it was just the name of the exception (like
  EvalError). Ideally in the future this would be a unique, easily
  googleable error ID (like rustc).

* "trace:" is now just "…". This assumes error contexts start with
  something like "while doing X".

Example before:

  error: --- AssertionError ---------------------------------------------------------------------------------------- nix
  at: (7:7) in file: /home/eelco/Dev/nixpkgs/pkgs/applications/misc/hello/default.nix

       6|
       7|   x = assert false; 1;
        |       ^
       8|

  assertion 'false' failed
  ----------------------------------------------------- show-trace -----------------------------------------------------
  trace: while evaluating the attribute 'x' of the derivation 'hello-2.10'
  at: (192:11) in file: /home/eelco/Dev/nixpkgs/pkgs/stdenv/generic/make-derivation.nix

     191|         // (lib.optionalAttrs (!(attrs ? name) && attrs ? pname && attrs ? version)) {
     192|           name = "${attrs.pname}-${attrs.version}";
        |           ^
     193|         } // (lib.optionalAttrs (stdenv.hostPlatform != stdenv.buildPlatform && !dontAddHostSuffix && (attrs ? name || (attrs ? pname && attrs ? version)))) {

Example after:

  error: assertion 'false' failed

         at: (7:7) in file: /home/eelco/Dev/nixpkgs/pkgs/applications/misc/hello/default.nix

              6|
              7|   x = assert false; 1;
               |       ^
              8|

         … while evaluating the attribute 'x' of the derivation 'hello-2.10'

         at: (192:11) in file: /home/eelco/Dev/nixpkgs/pkgs/stdenv/generic/make-derivation.nix

            191|         // (lib.optionalAttrs (!(attrs ? name) && attrs ? pname && attrs ? version)) {
            192|           name = "${attrs.pname}-${attrs.version}";
               |           ^
            193|         } // (lib.optionalAttrs (stdenv.hostPlatform != stdenv.buildPlatform && !dontAddHostSuffix && (attrs ? name || (attrs ? pname && attrs ? version)))) {
2021-01-21 11:02:09 +01:00

457 lines
9.7 KiB
C++

#include "nixexpr.hh"
#include "derivations.hh"
#include "util.hh"
#include <cstdlib>
namespace nix {
/* Displaying abstract syntax trees. */
std::ostream & operator << (std::ostream & str, const Expr & e)
{
e.show(str);
return str;
}
static void showString(std::ostream & str, const string & s)
{
str << '"';
for (auto c : (string) s)
if (c == '"' || c == '\\' || c == '$') str << "\\" << c;
else if (c == '\n') str << "\\n";
else if (c == '\r') str << "\\r";
else if (c == '\t') str << "\\t";
else str << c;
str << '"';
}
static void showId(std::ostream & str, const string & s)
{
if (s.empty())
str << "\"\"";
else if (s == "if") // FIXME: handle other keywords
str << '"' << s << '"';
else {
char c = s[0];
if (!((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || c == '_')) {
showString(str, s);
return;
}
for (auto c : s)
if (!((c >= 'a' && c <= 'z') ||
(c >= 'A' && c <= 'Z') ||
(c >= '0' && c <= '9') ||
c == '_' || c == '\'' || c == '-')) {
showString(str, s);
return;
}
str << s;
}
}
std::ostream & operator << (std::ostream & str, const Symbol & sym)
{
showId(str, *sym.s);
return str;
}
void Expr::show(std::ostream & str) const
{
abort();
}
void ExprInt::show(std::ostream & str) const
{
str << n;
}
void ExprFloat::show(std::ostream & str) const
{
str << nf;
}
void ExprString::show(std::ostream & str) const
{
showString(str, s);
}
void ExprPath::show(std::ostream & str) const
{
str << s;
}
void ExprVar::show(std::ostream & str) const
{
str << name;
}
void ExprSelect::show(std::ostream & str) const
{
str << "(" << *e << ")." << showAttrPath(attrPath);
if (def) str << " or (" << *def << ")";
}
void ExprOpHasAttr::show(std::ostream & str) const
{
str << "((" << *e << ") ? " << showAttrPath(attrPath) << ")";
}
void ExprAttrs::show(std::ostream & str) const
{
if (recursive) str << "rec ";
str << "{ ";
for (auto & i : attrs)
if (i.second.inherited)
str << "inherit " << i.first << " " << "; ";
else
str << i.first << " = " << *i.second.e << "; ";
for (auto & i : dynamicAttrs)
str << "\"${" << *i.nameExpr << "}\" = " << *i.valueExpr << "; ";
str << "}";
}
void ExprList::show(std::ostream & str) const
{
str << "[ ";
for (auto & i : elems)
str << "(" << *i << ") ";
str << "]";
}
void ExprLambda::show(std::ostream & str) const
{
str << "(";
if (matchAttrs) {
str << "{ ";
bool first = true;
for (auto & i : formals->formals) {
if (first) first = false; else str << ", ";
str << i.name;
if (i.def) str << " ? " << *i.def;
}
if (formals->ellipsis) {
if (!first) str << ", ";
str << "...";
}
str << " }";
if (!arg.empty()) str << " @ ";
}
if (!arg.empty()) str << arg;
str << ": " << *body << ")";
}
void ExprLet::show(std::ostream & str) const
{
str << "(let ";
for (auto & i : attrs->attrs)
if (i.second.inherited) {
str << "inherit " << i.first << "; ";
}
else
str << i.first << " = " << *i.second.e << "; ";
str << "in " << *body << ")";
}
void ExprWith::show(std::ostream & str) const
{
str << "(with " << *attrs << "; " << *body << ")";
}
void ExprIf::show(std::ostream & str) const
{
str << "(if " << *cond << " then " << *then << " else " << *else_ << ")";
}
void ExprAssert::show(std::ostream & str) const
{
str << "assert " << *cond << "; " << *body;
}
void ExprOpNot::show(std::ostream & str) const
{
str << "(! " << *e << ")";
}
void ExprConcatStrings::show(std::ostream & str) const
{
bool first = true;
str << "(";
for (auto & i : *es) {
if (first) first = false; else str << " + ";
str << *i;
}
str << ")";
}
void ExprPos::show(std::ostream & str) const
{
str << "__curPos";
}
std::ostream & operator << (std::ostream & str, const Pos & pos)
{
if (!pos)
str << "undefined position";
else
{
auto f = format(ANSI_BOLD "%1%" ANSI_NORMAL ":%2%:%3%");
switch (pos.origin) {
case foFile:
f % (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;
}
string showAttrPath(const AttrPath & attrPath)
{
std::ostringstream out;
bool first = true;
for (auto & i : attrPath) {
if (!first) out << '.'; else first = false;
if (i.symbol.set())
out << i.symbol;
else
out << "\"${" << *i.expr << "}\"";
}
return out.str();
}
Pos noPos;
/* Computing levels/displacements for variables. */
void Expr::bindVars(const StaticEnv & env)
{
abort();
}
void ExprInt::bindVars(const StaticEnv & env)
{
}
void ExprFloat::bindVars(const StaticEnv & env)
{
}
void ExprString::bindVars(const StaticEnv & env)
{
}
void ExprPath::bindVars(const StaticEnv & env)
{
}
void ExprVar::bindVars(const StaticEnv & env)
{
/* Check whether the variable appears in the environment. If so,
set its level and displacement. */
const StaticEnv * curEnv;
unsigned int level;
int withLevel = -1;
for (curEnv = &env, level = 0; curEnv; curEnv = curEnv->up, level++) {
if (curEnv->isWith) {
if (withLevel == -1) withLevel = level;
} else {
StaticEnv::Vars::const_iterator i = curEnv->vars.find(name);
if (i != curEnv->vars.end()) {
fromWith = false;
this->level = level;
displ = i->second;
return;
}
}
}
/* Otherwise, the variable must be obtained from the nearest
enclosing `with'. If there is no `with', then we can issue an
"undefined variable" error now. */
if (withLevel == -1)
throw UndefinedVarError({
.msg = hintfmt("undefined variable '%1%'", name),
.errPos = pos
});
fromWith = true;
this->level = withLevel;
}
void ExprSelect::bindVars(const StaticEnv & env)
{
e->bindVars(env);
if (def) def->bindVars(env);
for (auto & i : attrPath)
if (!i.symbol.set())
i.expr->bindVars(env);
}
void ExprOpHasAttr::bindVars(const StaticEnv & env)
{
e->bindVars(env);
for (auto & i : attrPath)
if (!i.symbol.set())
i.expr->bindVars(env);
}
void ExprAttrs::bindVars(const StaticEnv & env)
{
const StaticEnv * dynamicEnv = &env;
StaticEnv newEnv(false, &env);
if (recursive) {
dynamicEnv = &newEnv;
unsigned int displ = 0;
for (auto & i : attrs)
newEnv.vars[i.first] = i.second.displ = displ++;
for (auto & i : attrs)
i.second.e->bindVars(i.second.inherited ? env : newEnv);
}
else
for (auto & i : attrs)
i.second.e->bindVars(env);
for (auto & i : dynamicAttrs) {
i.nameExpr->bindVars(*dynamicEnv);
i.valueExpr->bindVars(*dynamicEnv);
}
}
void ExprList::bindVars(const StaticEnv & env)
{
for (auto & i : elems)
i->bindVars(env);
}
void ExprLambda::bindVars(const StaticEnv & env)
{
StaticEnv newEnv(false, &env);
unsigned int displ = 0;
if (!arg.empty()) newEnv.vars[arg] = displ++;
if (matchAttrs) {
for (auto & i : formals->formals)
newEnv.vars[i.name] = displ++;
for (auto & i : formals->formals)
if (i.def) i.def->bindVars(newEnv);
}
body->bindVars(newEnv);
}
void ExprLet::bindVars(const StaticEnv & env)
{
StaticEnv newEnv(false, &env);
unsigned int displ = 0;
for (auto & i : attrs->attrs)
newEnv.vars[i.first] = i.second.displ = displ++;
for (auto & i : attrs->attrs)
i.second.e->bindVars(i.second.inherited ? env : newEnv);
body->bindVars(newEnv);
}
void ExprWith::bindVars(const StaticEnv & env)
{
/* Does this `with' have an enclosing `with'? If so, record its
level so that `lookupVar' can look up variables in the previous
`with' if this one doesn't contain the desired attribute. */
const StaticEnv * curEnv;
unsigned int level;
prevWith = 0;
for (curEnv = &env, level = 1; curEnv; curEnv = curEnv->up, level++)
if (curEnv->isWith) {
prevWith = level;
break;
}
attrs->bindVars(env);
StaticEnv newEnv(true, &env);
body->bindVars(newEnv);
}
void ExprIf::bindVars(const StaticEnv & env)
{
cond->bindVars(env);
then->bindVars(env);
else_->bindVars(env);
}
void ExprAssert::bindVars(const StaticEnv & env)
{
cond->bindVars(env);
body->bindVars(env);
}
void ExprOpNot::bindVars(const StaticEnv & env)
{
e->bindVars(env);
}
void ExprConcatStrings::bindVars(const StaticEnv & env)
{
for (auto & i : *es)
i->bindVars(env);
}
void ExprPos::bindVars(const StaticEnv & env)
{
}
/* Storing function names. */
void Expr::setName(Symbol & name)
{
}
void ExprLambda::setName(Symbol & name)
{
this->name = name;
body->setName(name);
}
string ExprLambda::showNamePos() const
{
return (format("%1% at %2%") % (name.set() ? "'" + (string) name + "'" : "anonymous function") % pos).str();
}
/* Symbol table. */
size_t SymbolTable::totalSize() const
{
size_t n = 0;
for (auto & i : symbols)
n += i.size();
return n;
}
}