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xo-indentlog: presence flag for refrtag/xrefrtag

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This commit is contained in:
Roland Conybeare 2026-02-04 10:31:42 -05:00
commit 8cca5db5a1
2 changed files with 39 additions and 6 deletions
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17
xo-indentlog/include/xo/indentlog/print/pretty.hpp
View file

@ -256,6 +256,11 @@ namespace xo {
Member && member,
Rest&&... rest)
{
if constexpr (has_present<std::decay_t<Member>>) {
if (!member.present())
return this->print_upto_struct_members(ppii, rest...);
}
if (this->print_upto(" ") && this->print_upto(member))
return this->print_upto_struct_members(ppii, rest...);
@ -268,6 +273,13 @@ namespace xo {
Member && member,
Rest&&... rest)
{
if constexpr (has_present<std::decay_t<Member>>) {
if (!member.present()) {
this->pretty_struct_members(ppii, rest...);
return;
}
}
newline_indent(ppii.ci1());
this->pretty(member);
this->pretty_struct_members(ppii, rest...);
@ -381,6 +393,11 @@ namespace xo {
static bool print_pretty(const ppindentinfo & ppii,
const Tag & tag)
{
if constexpr (has_present<Tag>) {
if (!tag.present())
return true;
}
if (ppii.upto()) {
if (tag.prefix_space())
ppii.pps()->write(" ");

28
xo-indentlog/include/xo/indentlog/print/tag.hpp
View file

@ -6,6 +6,7 @@
#include "concat.hpp"
#include "quoted.hpp"
#include "color.hpp"
#include <concepts>
#include <iostream>
// STRINGIFY(xyz) -> "xyz"
@ -20,6 +21,12 @@
#define XTAG(x) xo::xtag(STRINGIFY(x), x)
namespace xo {
/** concept: true if T has a .present() method returning something bool-like **/
template <typename T>
concept has_present = requires(const T& t) {
{ t.present() } -> std::convertible_to<bool>;
};
enum class tagstyle {
/** print with automatic escapes for embedded special characters
* (any of ' ','"','\','\n','\r','\t').
@ -79,10 +86,13 @@ namespace xo {
**/
template <bool PrefixSpace, tagstyle TagStyle, typename Name, typename Value>
struct ref_tag_impl {
ref_tag_impl(Name const & n, Value const & v) : name_{n}, value_{v} {}
ref_tag_impl(Name && n, Value && v) : name_{std::forward<Name>(n)}, value_{std::forward<Value>(v)} {}
ref_tag_impl(Name const & n, Value const & v, bool present = true)
: name_{n}, value_{v}, present_{present} {}
ref_tag_impl(Name && n, Value && v, bool present = true)
: name_{std::forward<Name>(n)}, value_{std::forward<Value>(v)}, present_{present} {}
constexpr bool prefix_space() const { return PrefixSpace; }
bool present() const { return present_; }
Name const & name() const { return name_; }
Value const & value() const { return value_; }
@ -90,6 +100,7 @@ namespace xo {
private:
Name name_;
const Value& value_;
bool present_ = true;
};
// ----- xtag -----
@ -150,12 +161,14 @@ namespace xo {
/** 'reference raw tag'.
* 1. @p v must survive until refrtag is used (i.e. until tag inserted into some stream)
* 2. don't escape whitespace when printing value (pretty-printing with parseable structure)
*
* Print nothing if @p present is false
**/
template <typename Name, typename Value>
auto
refrtag(Name && n, Value && v)
refrtag(Name && n, Value && v, bool present = true)
{
return ref_tag_impl<false, tagstyle::raw, std::decay_t<Name>, std::decay_t<Value>>(n, v);
return ref_tag_impl<false, tagstyle::raw, std::decay_t<Name>, std::decay_t<Value>>(n, v, present);
}
// ----- xrefrtag -----
@ -164,9 +177,9 @@ namespace xo {
**/
template <typename Name, typename Value>
auto
xrefrtag(Name && n, Value && v)
xrefrtag(Name && n, Value && v, bool present = true)
{
return ref_tag_impl<true, tagstyle::raw, std::decay_t<Name>, std::decay_t<Value>>(n, v);
return ref_tag_impl<true, tagstyle::raw, std::decay_t<Name>, std::decay_t<Value>>(n, v, present);
}
// ----- operator<< on tag_impl -----
@ -199,6 +212,9 @@ namespace xo {
operator<<(std::ostream &s,
ref_tag_impl<PrefixSpace, TagStyle, Name, Value> const & tag)
{
if (!tag.present())
return s;
using xo::print::unq;
if (PrefixSpace)