Implement a suggestions mechanism

Each `Error` class now includes a set of suggestions, and these are printed by
the top-level handler.
This commit is contained in:
regnat 2022-03-03 10:50:35 +01:00
parent b09baf690b
commit c0792b1546
7 changed files with 191 additions and 6 deletions

View file

@ -610,17 +610,24 @@ std::pair<Value *, Pos> InstallableFlake::toValue(EvalState & state)
auto emptyArgs = state.allocBindings(0); auto emptyArgs = state.allocBindings(0);
Suggestions suggestions;
for (auto & attrPath : getActualAttrPaths()) { for (auto & attrPath : getActualAttrPaths()) {
try { try {
auto [v, pos] = findAlongAttrPath(state, attrPath, *emptyArgs, *vOutputs); auto [v, pos] = findAlongAttrPath(state, attrPath, *emptyArgs, *vOutputs);
state.forceValue(*v, pos); state.forceValue(*v, pos);
return {v, pos}; return {v, pos};
} catch (AttrPathNotFound & e) { } catch (AttrPathNotFound & e) {
suggestions += e.info().suggestions;
} }
} }
throw Error("flake '%s' does not provide attribute %s", throw Error(
flakeRef, showAttrPaths(getActualAttrPaths())); suggestions,
"flake '%s' does not provide attribute %s",
flakeRef,
showAttrPaths(getActualAttrPaths())
);
} }
std::vector<std::pair<std::shared_ptr<eval_cache::AttrCursor>, std::string>> std::vector<std::pair<std::shared_ptr<eval_cache::AttrCursor>, std::string>>

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@ -74,8 +74,14 @@ std::pair<Value *, Pos> findAlongAttrPath(EvalState & state, const std::string &
throw Error("empty attribute name in selection path '%1%'", attrPath); throw Error("empty attribute name in selection path '%1%'", attrPath);
Bindings::iterator a = v->attrs->find(state.symbols.create(attr)); Bindings::iterator a = v->attrs->find(state.symbols.create(attr));
if (a == v->attrs->end()) if (a == v->attrs->end()) {
throw AttrPathNotFound("attribute '%1%' in selection path '%2%' not found", attr, attrPath); std::set<std::string> attrNames;
for (auto & attr : *v->attrs)
attrNames.insert(attr.name);
auto suggestions = Suggestions::bestMatches(attrNames, attr);
throw AttrPathNotFound(suggestions, "attribute '%1%' in selection path '%2%' not found", attr, attrPath);
}
v = &*a->value; v = &*a->value;
pos = *a->pos; pos = *a->pos;
} }

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@ -328,8 +328,13 @@ MultiCommand::MultiCommand(const Commands & commands_)
completions->add(name); completions->add(name);
} }
auto i = commands.find(s); auto i = commands.find(s);
if (i == commands.end()) if (i == commands.end()) {
throw UsageError("'%s' is not a recognised command", s); std::set<std::string> commandNames;
for (auto & [name, _] : commands)
commandNames.insert(name);
auto suggestions = Suggestions::bestMatches(commandNames, s);
throw UsageError(suggestions, "'%s' is not a recognised command", s);
}
command = {s, i->second()}; command = {s, i->second()};
command->second->parent = this; command->second->parent = this;
}} }}

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@ -282,6 +282,13 @@ std::ostream & showErrorInfo(std::ostream & out, const ErrorInfo & einfo, bool s
} }
} }
auto suggestions = einfo.suggestions.trim();
if (! suggestions.suggestions.empty()){
oss << "Did you mean " <<
suggestions.trim().pretty_print() <<
"?" << std::endl;
}
// traces // traces
if (showTrace && !einfo.traces.empty()) { if (showTrace && !einfo.traces.empty()) {
for (auto iter = einfo.traces.rbegin(); iter != einfo.traces.rend(); ++iter) { for (auto iter = einfo.traces.rbegin(); iter != einfo.traces.rend(); ++iter) {

View file

@ -1,5 +1,6 @@
#pragma once #pragma once
#include "suggestions.hh"
#include "ref.hh" #include "ref.hh"
#include "types.hh" #include "types.hh"
#include "fmt.hh" #include "fmt.hh"
@ -112,6 +113,8 @@ struct ErrorInfo {
std::optional<ErrPos> errPos; std::optional<ErrPos> errPos;
std::list<Trace> traces; std::list<Trace> traces;
Suggestions suggestions;
static std::optional<std::string> programName; static std::optional<std::string> programName;
}; };
@ -141,6 +144,11 @@ public:
: err { .level = lvlError, .msg = hintfmt(fs, args...) } : err { .level = lvlError, .msg = hintfmt(fs, args...) }
{ } { }
template<typename... Args>
BaseError(const Suggestions & sug, const Args & ... args)
: err { .level = lvlError, .msg = hintfmt(args...), .suggestions = sug }
{ }
BaseError(hintformat hint) BaseError(hintformat hint)
: err { .level = lvlError, .msg = hint } : err { .level = lvlError, .msg = hint }
{ } { }

111
src/libutil/suggestions.cc Normal file
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@ -0,0 +1,111 @@
#include "suggestions.hh"
#include "ansicolor.hh"
#include "util.hh"
#include <algorithm>
namespace nix {
/**
* Return `some(distance)` where distance is an integer representing some
* notion of distance between both arguments.
*
* If the distance is too big, return none
*/
int distanceBetween(std::string_view first, std::string_view second)
{
// Levenshtein distance.
// Implementation borrowed from
// https://en.wikipedia.org/wiki/Levenshtein_distance#Iterative_with_two_matrix_rows
int m = first.size();
int n = second.size();
auto v0 = std::vector<int>(n+1);
auto v1 = std::vector<int>(n+1);
for (auto i = 0; i <= n; i++)
v0[i] = i;
for (auto i = 0; i < m; i++) {
v1[0] = i+1;
for (auto j = 0; j < n; j++) {
auto deletionCost = v0[j+1] + 1;
auto insertionCost = v1[j] + 1;
auto substitutionCost = first[i] == second[j] ? v0[j] : v0[j] + 1;
v1[j+1] = std::min({deletionCost, insertionCost, substitutionCost});
}
std::swap(v0, v1);
}
return v0[n];
}
Suggestions Suggestions::bestMatches (
std::set<std::string> allMatches,
std::string query)
{
std::set<Suggestion> res;
for (const auto & possibleMatch : allMatches) {
res.insert(Suggestion {
.distance = distanceBetween(query, possibleMatch),
.suggestion = possibleMatch,
});
}
return Suggestions { res };
}
Suggestions Suggestions::trim(int limit, int maxDistance) const
{
std::set<Suggestion> res;
int count = 0;
for (auto & elt : suggestions) {
if (count >= limit || elt.distance >= maxDistance)
break;
count++;
res.insert(elt);
}
return Suggestions{res};
}
std::string Suggestion::pretty_print() const
{
return ANSI_WARNING + filterANSIEscapes(suggestion) + ANSI_NORMAL;
}
std::string Suggestions::pretty_print() const
{
switch (suggestions.size()) {
case 0:
return "";
case 1:
return suggestions.begin()->pretty_print();
default: {
std::string res = "one of ";
auto iter = suggestions.begin();
res += iter->pretty_print(); // Iter cant be end() because the container isnt null
iter++;
auto last = suggestions.end(); last--;
for ( ; iter != suggestions.end() ; iter++) {
res += (iter == last) ? " or " : ", ";
res += iter->pretty_print();
}
return res;
}
}
}
Suggestions & Suggestions::operator+=(const Suggestions & other)
{
suggestions.insert(
other.suggestions.begin(),
other.suggestions.end()
);
return *this;
}
}

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@ -0,0 +1,41 @@
#pragma once
#include "comparator.hh"
#include "types.hh"
#include <set>
namespace nix {
/**
* A potential suggestion for the cli interface.
*/
class Suggestion {
public:
int distance; // The smaller the better
std::string suggestion;
std::string pretty_print() const;
GENERATE_CMP(Suggestion, me->distance, me->suggestion)
};
class Suggestions {
public:
std::set<Suggestion> suggestions;
std::string pretty_print() const;
Suggestions trim(
int limit = 5,
int maxDistance = 2
) const;
static Suggestions bestMatches (
std::set<std::string> allMatches,
std::string query
);
Suggestions& operator+=(const Suggestions & other);
};
}