fish-shell/src/future_feature_flags.h
Johannes Altmanninger cc32b4f2a7 Make '&' only background if followed by a separating character
This is opt-in through a new feature flag "ampersand-nobg-in-token".

When this flag and "qmark-noglob" are enabled, this command no longer
needs quoting:

	curl https://example.com/thing?foo=bar&duran=duran

Compared to the previous approach e1570a4 ("Let '&' only separate as
the first char of a word"), this has some advantages:

1. "&&" and "&>" are no longer affected. They are still special, even
   if used between tokens without spaces, like "echo bar&>foo".
   Maybe this is not really *better*, but it avoids risking to annoy
   users by breaking the old variant.

2. "&" is still special if at the end of a token, like in "sleep 1&".

Word movement is not affected by the semantics change, so Alt-F and
friends still stop at every "&".
2021-07-23 22:58:51 +02:00

106 lines
3.2 KiB
C++

// Flags to enable upcoming features
#ifndef FISH_FUTURE_FEATURE_FLAGS_H
#define FISH_FUTURE_FEATURE_FLAGS_H
#include <assert.h>
#include <atomic>
#include <unordered_map>
#include "common.h"
class features_t {
public:
/// The list of flags.
enum flag_t {
/// Whether ^ is supported for stderr redirection.
stderr_nocaret,
/// Whether ? is supported as a glob.
qmark_noglob,
/// Whether string replace -r double-unescapes the replacement.
string_replace_backslash,
/// Whether "&" is not-special if followed by a word character.
ampersand_nobg_in_token,
/// The number of flags.
flag_count
};
/// Return whether a flag is set.
bool test(flag_t f) const {
assert(f >= 0 && f < flag_count && "Invalid flag");
return values[f].load(std::memory_order_relaxed);
}
/// Set a flag.
void set(flag_t f, bool value) {
assert(f >= 0 && f < flag_count && "Invalid flag");
values[f].store(value, std::memory_order_relaxed);
}
/// Parses a comma-separated feature-flag string, updating ourselves with the values.
/// Feature names or group names may be prefixed with "no-" to disable them.
/// The special group name "all" may be used for those who like to live on the edge.
/// Unknown features are silently ignored.
void set_from_string(const wcstring &str);
/// Metadata about feature flags.
struct metadata_t {
/// The flag itself.
features_t::flag_t flag;
/// User-presentable short name of the feature flag.
const wchar_t *name;
/// Comma-separated list of feature groups.
const wchar_t *groups;
/// User-presentable description of the feature flag.
const wchar_t *description;
/// Default flag value.
const bool default_value;
};
/// The metadata, indexed by flag.
static const metadata_t metadata[flag_count];
/// Return the metadata for a particular name, or nullptr if not found.
static const struct metadata_t *metadata_for(const wchar_t *name);
/// The singleton shared feature set.
static features_t global_features;
features_t();
features_t(const features_t &rhs) { *this = rhs; }
void operator=(const features_t &rhs) {
for (int i = 0; i < flag_count; i++) {
flag_t f = static_cast<flag_t>(i);
this->set(f, rhs.test(f));
}
}
private:
// Values for the flags.
// These are atomic to "fix" a race reported by tsan where tests of feature flags and other
// tests which use them conceptually race.
std::atomic<bool> values[flag_count]{};
};
/// Return the global set of features for fish. This is const to prevent accidental mutation.
inline const features_t &fish_features() { return features_t::global_features; }
/// Perform a feature test on the global set of features.
inline bool feature_test(features_t::flag_t f) { return fish_features().test(f); }
/// Return the global set of features for fish, but mutable. In general fish features should be set
/// at startup only.
inline features_t &mutable_fish_features() { return features_t::global_features; }
#endif