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https://github.com/NixOS/nix
synced 2025-06-28 01:11:15 +02:00
Unify and refactor value printing
Previously, there were two mostly-identical value printers -- one in `libexpr/eval.cc` (which didn't force values) and one in `libcmd/repl.cc` (which did force values and also printed ANSI color codes). This PR unifies both of these printers into `print.cc` and provides a `PrintOptions` struct for controlling the output, which allows for toggling whether values are forced, whether repeated values are tracked, and whether ANSI color codes are displayed. Additionally, `PrintOptions` allows tuning the maximum number of attributes, list items, and bytes in a string that will be displayed; this makes it ideal for contexts where printing too much output (e.g. all of Nixpkgs) is distracting. (As requested by @roberth in https://github.com/NixOS/nix/pull/9554#issuecomment-1845095735) Please read the tests for example output. Future work: - It would be nice to provide this function as a builtin, perhaps `builtins.toStringDebug` -- a printing function that never fails would be useful when debugging Nix code. - It would be nice to support customizing `PrintOptions` members on the command line, e.g. `--option to-string-max-attrs 1000`.
This commit is contained in:
Rebecca Turner
parent
c9125603a5
commit
0fa08b4516
18 changed files with 1174 additions and 278 deletions
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@ -1,24 +1,66 @@
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#include "print.hh"
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#include <limits>
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#include <unordered_set>
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#include "print.hh"
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#include "ansicolor.hh"
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#include "signals.hh"
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#include "store-api.hh"
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#include "terminal.hh"
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#include "english.hh"
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namespace nix {
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std::ostream &
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printLiteralString(std::ostream & str, const std::string_view string)
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void printElided(
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std::ostream & output,
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unsigned int value,
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const std::string_view single,
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const std::string_view plural,
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bool ansiColors)
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{
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if (ansiColors)
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output << ANSI_FAINT;
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output << " «";
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pluralize(output, value, single, plural);
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output << " elided»";
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if (ansiColors)
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output << ANSI_NORMAL;
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}
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std::ostream &
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printLiteralString(std::ostream & str, const std::string_view string, size_t maxLength, bool ansiColors)
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{
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size_t charsPrinted = 0;
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if (ansiColors)
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str << ANSI_MAGENTA;
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str << "\"";
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for (auto i = string.begin(); i != string.end(); ++i) {
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if (charsPrinted >= maxLength) {
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str << "\"";
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printElided(str, string.length() - charsPrinted, "byte", "bytes", ansiColors);
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return str;
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}
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if (*i == '\"' || *i == '\\') str << "\\" << *i;
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else if (*i == '\n') str << "\\n";
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else if (*i == '\r') str << "\\r";
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else if (*i == '\t') str << "\\t";
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else if (*i == '$' && *(i+1) == '{') str << "\\" << *i;
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else str << *i;
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charsPrinted++;
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}
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str << "\"";
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if (ansiColors)
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str << ANSI_NORMAL;
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return str;
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}
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std::ostream &
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printLiteralString(std::ostream & str, const std::string_view string)
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{
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return printLiteralString(str, string, std::numeric_limits<size_t>::max(), false);
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}
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std::ostream &
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printLiteralBool(std::ostream & str, bool boolean)
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{
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@ -90,5 +132,373 @@ printAttributeName(std::ostream & str, std::string_view name) {
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return str;
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}
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bool isImportantAttrName(const std::string& attrName)
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{
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return attrName == "type" || attrName == "_type";
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}
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typedef std::pair<std::string, Value *> AttrPair;
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struct ImportantFirstAttrNameCmp
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{
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bool operator()(const AttrPair& lhs, const AttrPair& rhs) const
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{
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auto lhsIsImportant = isImportantAttrName(lhs.first);
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auto rhsIsImportant = isImportantAttrName(rhs.first);
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return std::forward_as_tuple(!lhsIsImportant, lhs.first)
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< std::forward_as_tuple(!rhsIsImportant, rhs.first);
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}
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};
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typedef std::set<Value *> ValuesSeen;
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class Printer
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{
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private:
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std::ostream & output;
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EvalState & state;
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PrintOptions options;
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std::optional<ValuesSeen> seen;
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void printRepeated()
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{
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if (options.ansiColors)
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output << ANSI_MAGENTA;
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output << "«repeated»";
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if (options.ansiColors)
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output << ANSI_NORMAL;
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}
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void printNullptr()
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{
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if (options.ansiColors)
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output << ANSI_MAGENTA;
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output << "«nullptr»";
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if (options.ansiColors)
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output << ANSI_NORMAL;
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}
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void printElided(unsigned int value, const std::string_view single, const std::string_view plural)
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{
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::nix::printElided(output, value, single, plural, options.ansiColors);
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}
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void printInt(Value & v)
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{
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if (options.ansiColors)
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output << ANSI_CYAN;
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output << v.integer;
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if (options.ansiColors)
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output << ANSI_NORMAL;
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}
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void printFloat(Value & v)
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{
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if (options.ansiColors)
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output << ANSI_CYAN;
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output << v.fpoint;
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if (options.ansiColors)
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output << ANSI_NORMAL;
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}
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void printBool(Value & v)
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{
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if (options.ansiColors)
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output << ANSI_CYAN;
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printLiteralBool(output, v.boolean);
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if (options.ansiColors)
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output << ANSI_NORMAL;
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}
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void printString(Value & v)
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{
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printLiteralString(output, v.string_view(), options.maxStringLength, options.ansiColors);
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}
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void printPath(Value & v)
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{
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if (options.ansiColors)
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output << ANSI_GREEN;
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output << v.path().to_string(); // !!! escaping?
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if (options.ansiColors)
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output << ANSI_NORMAL;
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}
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void printNull()
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{
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if (options.ansiColors)
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output << ANSI_CYAN;
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output << "null";
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if (options.ansiColors)
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output << ANSI_NORMAL;
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}
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void printDerivation(Value & v)
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{
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try {
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Bindings::iterator i = v.attrs->find(state.sDrvPath);
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NixStringContext context;
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std::string storePath;
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if (i != v.attrs->end())
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storePath = state.store->printStorePath(state.coerceToStorePath(i->pos, *i->value, context, "while evaluating the drvPath of a derivation"));
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if (options.ansiColors)
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output << ANSI_GREEN;
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output << "«derivation";
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if (!storePath.empty()) {
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output << " " << storePath;
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}
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output << "»";
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if (options.ansiColors)
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output << ANSI_NORMAL;
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} catch (BaseError & e) {
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printError_(e);
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}
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}
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void printAttrs(Value & v, size_t depth)
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{
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if (seen && !seen->insert(&v).second) {
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printRepeated();
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return;
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}
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if (options.force && options.derivationPaths && state.isDerivation(v)) {
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printDerivation(v);
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} else if (depth < options.maxDepth) {
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output << "{ ";
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std::vector<std::pair<std::string, Value *>> sorted;
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for (auto & i : *v.attrs)
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sorted.emplace_back(std::pair(state.symbols[i.name], i.value));
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if (options.maxAttrs == std::numeric_limits<size_t>::max())
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std::sort(sorted.begin(), sorted.end());
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else
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std::sort(sorted.begin(), sorted.end(), ImportantFirstAttrNameCmp());
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size_t attrsPrinted = 0;
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for (auto & i : sorted) {
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if (attrsPrinted >= options.maxAttrs) {
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printElided(sorted.size() - attrsPrinted, "attribute", "attributes");
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break;
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}
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printAttributeName(output, i.first);
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output << " = ";
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print(*i.second, depth + 1);
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output << "; ";
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attrsPrinted++;
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}
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output << "}";
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} else
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output << "{ ... }";
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}
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void printList(Value & v, size_t depth)
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{
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if (seen && v.listSize() && !seen->insert(&v).second) {
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printRepeated();
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return;
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}
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output << "[ ";
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if (depth < options.maxDepth) {
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size_t listItemsPrinted = 0;
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for (auto elem : v.listItems()) {
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if (listItemsPrinted >= options.maxListItems) {
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printElided(v.listSize() - listItemsPrinted, "item", "items");
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break;
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}
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if (elem) {
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print(*elem, depth + 1);
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} else {
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printNullptr();
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}
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output << " ";
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listItemsPrinted++;
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}
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}
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else
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output << "... ";
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output << "]";
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}
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void printFunction(Value & v)
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{
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if (options.ansiColors)
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output << ANSI_BLUE;
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output << "«";
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if (v.isLambda()) {
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output << "lambda";
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if (v.lambda.fun) {
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if (v.lambda.fun->name) {
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output << " " << state.symbols[v.lambda.fun->name];
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}
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std::ostringstream s;
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s << state.positions[v.lambda.fun->pos];
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output << " @ " << filterANSIEscapes(s.str());
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}
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} else if (v.isPrimOp()) {
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if (v.primOp)
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output << *v.primOp;
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else
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output << "primop";
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} else if (v.isPrimOpApp()) {
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output << "partially applied ";
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auto primOp = v.primOpAppPrimOp();
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if (primOp)
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output << *primOp;
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else
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output << "primop";
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} else {
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abort();
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}
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output << "»";
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if (options.ansiColors)
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output << ANSI_NORMAL;
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}
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void printThunk(Value & v)
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{
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if (v.isBlackhole()) {
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// Although we know for sure that it's going to be an infinite recursion
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// when this value is accessed _in the current context_, it's likely
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// that the user will misinterpret a simpler «infinite recursion» output
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// as a definitive statement about the value, while in fact it may be
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// a valid value after `builtins.trace` and perhaps some other steps
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// have completed.
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if (options.ansiColors)
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output << ANSI_RED;
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output << "«potential infinite recursion»";
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if (options.ansiColors)
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output << ANSI_NORMAL;
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} else if (v.isThunk() || v.isApp()) {
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if (options.ansiColors)
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output << ANSI_MAGENTA;
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output << "«thunk»";
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if (options.ansiColors)
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output << ANSI_NORMAL;
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} else {
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abort();
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}
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}
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void printExternal(Value & v)
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{
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v.external->print(output);
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}
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void printUnknown()
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{
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if (options.ansiColors)
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output << ANSI_RED;
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output << "«unknown»";
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if (options.ansiColors)
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output << ANSI_NORMAL;
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}
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void printError_(BaseError & e)
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{
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if (options.ansiColors)
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output << ANSI_RED;
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output << "«" << e.msg() << "»";
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if (options.ansiColors)
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output << ANSI_NORMAL;
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}
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void print(Value & v, size_t depth)
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{
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output.flush();
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checkInterrupt();
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if (options.force) {
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try {
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state.forceValue(v, v.determinePos(noPos));
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} catch (BaseError & e) {
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printError_(e);
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return;
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}
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}
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switch (v.type()) {
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case nInt:
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printInt(v);
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break;
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case nFloat:
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printFloat(v);
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break;
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case nBool:
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printBool(v);
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break;
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case nString:
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printString(v);
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break;
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case nPath:
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printPath(v);
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break;
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case nNull:
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printNull();
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break;
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case nAttrs:
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printAttrs(v, depth);
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break;
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case nList:
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printList(v, depth);
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break;
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case nFunction:
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printFunction(v);
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break;
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case nThunk:
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printThunk(v);
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break;
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case nExternal:
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printExternal(v);
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break;
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default:
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printUnknown();
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break;
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}
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}
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public:
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Printer(std::ostream & output, EvalState & state, PrintOptions options)
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: output(output), state(state), options(options) { }
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void print(Value & v)
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{
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if (options.trackRepeated) {
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seen.emplace();
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} else {
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seen.reset();
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}
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ValuesSeen seen;
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print(v, 0);
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}
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};
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void printValue(EvalState & state, std::ostream & output, Value & v, PrintOptions options)
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{
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Printer(output, state, options).print(v);
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}
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}
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