fish-shell/src/operation_context.h
ridiculousfish 0f7bba5f0e Introduce operation_context_t
This commit recognizes an existing pattern: many operations need some
combination of a set of variables, a way to detect cancellation, and
sometimes a parser. For example, tab completion needs a parser to execute
custom completions, the variable set, should cancel on SIGINT. Background
autosuggestions don't need a parser, but they do need the variables and
should cancel if the user types something new. Etc.

This introduces a new triple operation_context_t that wraps these concepts
up. This simplifies many method signatures and argument passing.
2020-01-16 15:21:28 -08:00

56 lines
2 KiB
C++

#ifndef FISH_OPERATION_CONTEXT_H
#define FISH_OPERATION_CONTEXT_H
#include <memory>
#include "common.h"
class environment_t;
class parser_t;
/// A common helper which always returns false.
bool no_cancel();
/// A operation_context_t is a simple property bag which wraps up data needed for highlighting,
/// expansion, completion, and more.
/// It contains the following triple:
/// 1. A parser. This is often null. If not null, it may be used to execute fish script. If null,
/// then this is a background operation and fish script must not be executed.
/// 2. A variable set. This is never null. This may differ from the variables in the parser.
/// 3. A cancellation checker. This is a function which you may call to detect that the operation
/// is no longer necessary and should be cancelled.
class operation_context_t {
public:
// The parser, if this is a foreground operation. If this is a background operation, this may be
// nullptr.
std::shared_ptr<parser_t> parser;
// The set of variables. It is the creator's responsibility to ensure this lives as log as the
// context itself.
const environment_t &vars;
// A function which may be used to poll for cancellation.
cancel_checker_t cancel_checker;
// Invoke the cancel checker. \return if we should cancel.
bool check_cancel() const { return cancel_checker(); }
// \return an "empty" context which contains no variables, no parser, and never cancels.
static operation_context_t empty();
// \return an operation context that contains only global variables, no parser, and never
// cancels.
static operation_context_t globals();
/// Construct from the full triple of a parser, vars, and cancel checker.
operation_context_t(std::shared_ptr<parser_t> parser, const environment_t &vars,
cancel_checker_t cancel_checker);
/// Construct from vars alone.
explicit operation_context_t(const environment_t &vars)
: operation_context_t(nullptr, vars, no_cancel) {}
~operation_context_t();
};
#endif