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Shell: Improve the parsing of history event designators

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TheFightingCatfish 2021-07-30 18:55:57 +08:00 committed by Ali Mohammad Pur
parent 05c3755e62
commit f67c2c97b1
Notes: sideshowbarker 2024-07-18 07:37:34 +09:00 
Author: https://github.com/SeekingBlues
Commit: https://github.com/SerenityOS/serenity/commit/f67c2c97b11
Pull-request: https://github.com/SerenityOS/serenity/pull/9109
Reviewed-by: https://github.com/alimpfard
3 changed files with 98 additions and 72 deletions
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27
Base/usr/share/man/man5/Shell.md
View file

@ -362,20 +362,25 @@ match "$(make_some_value)" {
History expansion may be utilized to reuse previously typed words or commands.
Such expressions are of the general form `!<event_designator>(:<word_designator>)`, where `event_designator` would select an entry in the shell history, and `word_designator` would select a word (or a range of words) from that entry.
| Event designator | effect |
| Event designator | Effect |
| :- | :----- |
| `!` | Select the immediately preceding command |
| _n_ | Select the _n_'th entry in the history |
| -_n_ | Select the last _n_'th entry in the history |
| _str_ | Select the most recent entry starting with _str_ |
| ?_str_ | Select the most recent entry containing _str_ |
| `!` | The immediately preceding command |
| _n_ | The _n_'th entry in the history, starting with 1 as the first entry |
| -_n_ | The last _n_'th entry in the history, starting with -1 as the previous entry |
| _str_ | The most recent entry starting with _str_ |
| `?`_str_ | The most recent entry containing _str_ |
| Word designator | effect |
| Word designator | Effect |
| :-- | :----- |
| _n_ | The _n_'th word, starting with 0 as the command |
| `^` | The first word (index 0) |
| `$` | The last word |
| _x_-_y_ | The range of words starting at _x_ and ending at _y_ (inclusive) |
| _n_ | The word at index _n_, starting with 0 as the first word (usually the command) |
| `^` | The first argument (index 1) |
| `$` | The last argument |
| _x_-_y_ | The range of words starting at _x_ and ending at _y_ (inclusive). _x_ defaults to 0 if omitted |
| `*` | All the arguments. Equivalent to `^`-`$` |
| _x_`*` | The range of words starting at _x_ and ending at the last word (`$`) (inclusive) |
| _x_- | The range of words starting at _x_ and ending at the second to last word (inclusive). _x_ defaults to 0 if omitted |
Note: The event designator and the word designator should usually be separated by a colon (`:`). This colon can be omitted only if the word designator starts with `^`, `$` or `*` (such as `!1^` for the first argument of the first entry in the history).
## Formal Grammar

2
Userland/Shell/AST.h
View file

@ -917,7 +917,7 @@ struct HistorySelector {
if (kind == Index)
return selector;
if (kind == Last)
return size - 1;
return size - selector - 1;
VERIFY_NOT_REACHED();
}
};

141
Userland/Shell/Parser.cpp
View file

@ -1,5 +1,5 @@
/*
* Copyright (c) 2020, the SerenityOS developers.
* Copyright (c) 2020-2021, the SerenityOS developers.
*
* SPDX-License-Identifier: BSD-2-Clause
*/
@ -1589,7 +1589,17 @@ RefPtr<AST::Node> Parser::parse_history_designator()
nullptr }
};
bool is_word_selector = false;
switch (peek()) {
case ':':
consume();
[[fallthrough]];
case '^':
case '$':
case '*':
is_word_selector = true;
break;
case '!':
consume();
selector.event.kind = AST::HistorySelector::EventKind::IndexFromEnd;
@ -1601,7 +1611,7 @@ RefPtr<AST::Node> Parser::parse_history_designator()
selector.event.kind = AST::HistorySelector::EventKind::ContainingStringLookup;
[[fallthrough]];
default: {
TemporaryChange chars_change { m_extra_chars_not_allowed_in_barewords, { ':' } };
TemporaryChange chars_change { m_extra_chars_not_allowed_in_barewords, { ':', '^', '$', '*' } };
auto bareword = parse_bareword();
if (!bareword || !bareword->is_bareword()) {
@ -1622,91 +1632,102 @@ RefPtr<AST::Node> Parser::parse_history_designator()
selector.event.kind = AST::HistorySelector::EventKind::IndexFromEnd;
else
selector.event.kind = AST::HistorySelector::EventKind::IndexFromStart;
auto number = selector.event.text.to_int();
if (number.has_value())
selector.event.index = abs(number.value());
auto number = abs(selector.event.text.to_int().value_or(0));
if (number != 0)
selector.event.index = number - 1;
else
syntax_error = create<AST::SyntaxError>("History entry index value invalid or out of range");
}
break;
if (":^$*"sv.contains(peek())) {
is_word_selector = true;
if (peek() == ':')
consume();
}
}
}
if (peek() != ':') {
if (!is_word_selector) {
auto node = create<AST::HistoryEvent>(move(selector));
if (syntax_error)
node->set_is_syntax_error(*syntax_error);
return node;
}
consume();
// Word selectors
auto parse_word_selector = [&]() -> Optional<AST::HistorySelector::WordSelector> {
auto rule_start = push_start();
auto c = peek();
AST::HistorySelector::WordSelectorKind word_selector_kind;
ssize_t offset = -1;
if (isdigit(c)) {
auto num = consume_while(is_digit);
auto value = num.to_uint();
if (!value.has_value()) {
return AST::HistorySelector::WordSelector {
AST::HistorySelector::WordSelectorKind::Index,
0,
{ m_rule_start_offsets.last(), m_offset, m_rule_start_lines.last(), line() },
syntax_error ? NonnullRefPtr(*syntax_error) : create<AST::SyntaxError>("Word selector value invalid or out of range")
};
}
return AST::HistorySelector::WordSelector {
AST::HistorySelector::WordSelectorKind::Index,
value.value(),
{ m_rule_start_offsets.last(), m_offset, m_rule_start_lines.last(), line() },
syntax_error
};
}
if (c == '^') {
if (!value.has_value())
return {};
word_selector_kind = AST::HistorySelector::WordSelectorKind::Index;
offset = value.value();
} else if (c == '^') {
consume();
return AST::HistorySelector::WordSelector {
AST::HistorySelector::WordSelectorKind::Index,
0,
{ m_rule_start_offsets.last(), m_offset, m_rule_start_lines.last(), line() },
syntax_error
};
}
if (c == '$') {
word_selector_kind = AST::HistorySelector::WordSelectorKind::Index;
offset = 1;
} else if (c == '$') {
consume();
return AST::HistorySelector::WordSelector {
AST::HistorySelector::WordSelectorKind::Last,
0,
{ m_rule_start_offsets.last(), m_offset, m_rule_start_lines.last(), line() },
syntax_error
};
word_selector_kind = AST::HistorySelector::WordSelectorKind::Last;
offset = 0;
}
return {};
if (offset == -1)
return {};
return AST::HistorySelector::WordSelector {
word_selector_kind,
static_cast<size_t>(offset),
{ m_rule_start_offsets.last(), m_offset, m_rule_start_lines.last(), line() },
syntax_error
};
};
auto start = parse_word_selector();
if (!start.has_value()) {
auto make_word_selector = [&](AST::HistorySelector::WordSelectorKind word_selector_kind, size_t offset) {
return AST::HistorySelector::WordSelector {
word_selector_kind,
offset,
{ m_rule_start_offsets.last(), m_offset, m_rule_start_lines.last(), line() },
syntax_error
};
};
auto first_char = peek();
if (!(is_digit(first_char) || "^$-*"sv.contains(first_char))) {
if (!syntax_error)
syntax_error = create<AST::SyntaxError>("Expected a word selector after ':' in a history event designator", true);
auto node = create<AST::HistoryEvent>(move(selector));
node->set_is_syntax_error(*syntax_error);
return node;
}
selector.word_selector_range.start = start.release_value();
if (peek() == '-') {
} else if (first_char == '*') {
consume();
auto end = parse_word_selector();
if (!end.has_value()) {
if (!syntax_error)
syntax_error = create<AST::SyntaxError>("Expected a word selector after '-' in a history event designator word selector", true);
auto node = create<AST::HistoryEvent>(move(selector));
node->set_is_syntax_error(*syntax_error);
return node;
}
selector.word_selector_range.end = move(end);
selector.word_selector_range.start = make_word_selector(AST::HistorySelector::WordSelectorKind::Index, 1);
selector.word_selector_range.end = make_word_selector(AST::HistorySelector::WordSelectorKind::Last, 0);
} else if (first_char == '-') {
consume();
selector.word_selector_range.start = make_word_selector(AST::HistorySelector::WordSelectorKind::Index, 0);
auto last_selector = parse_word_selector();
if (!last_selector.has_value())
selector.word_selector_range.end = make_word_selector(AST::HistorySelector::WordSelectorKind::Last, 1);
else
selector.word_selector_range.end = last_selector.release_value();
} else {
selector.word_selector_range.end.clear();
auto first_selector = parse_word_selector();
// peek() should be a digit, ^, or $ here, so this should always have value.
VERIFY(first_selector.has_value());
selector.word_selector_range.start = first_selector.release_value();
if (peek() == '-') {
consume();
auto last_selector = parse_word_selector();
if (last_selector.has_value()) {
selector.word_selector_range.end = last_selector.release_value();
} else {
selector.word_selector_range.end = make_word_selector(AST::HistorySelector::WordSelectorKind::Last, 1);
}
} else if (peek() == '*') {
consume();
selector.word_selector_range.end = make_word_selector(AST::HistorySelector::WordSelectorKind::Last, 0);
} else {
selector.word_selector_range.end.clear();
}
}
auto node = create<AST::HistoryEvent>(move(selector));