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Add parsing of variable definitions
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@adaszko
adaszko committed Jun 9, 2023
1 parent 1320c15 commit 1a72916
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4 changes: 2 additions & 2 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -71,7 +71,7 @@ Use parentheses to group patterns:

* Printing of undefined variables as a gentle warning.

* `name ::= expression;` defines a new production that can be referred to from other productions via `<name>`
* `<name> ::= expression;` defines a new production that can be referred to from other productions via `<name>`
syntax. Referring to a production recursively won't be supported as that would take us outside of regular languages.

* Produce [railroad diagrams](https://github.com/lukaslueg/railroad) to ease grammar development.
Expand All @@ -80,7 +80,7 @@ Use parentheses to group patterns:

* Generate grammars automatically from man pages similarly to [how Fish shell is does it](https://github.com/fish-shell/fish-shell/blob/946ecf235c002cff596fbbb2c03f9693c30744da/share/tools/create_manpage_completions.py).

* Show completion hints in ZSH and Fish (Bash does not support them).
* Show completion hints in ZSH and Fish (Bash does not support them): `--invert-match "select non-matching lines"`

* `name = { shell-command... }` defines a variable that uses a shell command to generate suggested
completions. The shell command should print one suggested completion per line. The `$COMP_LINE` and
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114 changes: 96 additions & 18 deletions src/grammar.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,7 @@ use nom::{
branch::alt,
bytes::complete::{is_not, tag, take_while1, escaped},
character::{complete::{char, multispace0, multispace1, one_of}, is_alphanumeric},
multi::separated_list1,
multi::many0,
IResult, combinator::fail, error::context,
};

Expand All @@ -13,6 +13,7 @@ use ustr::{Ustr, ustr};
pub struct Grammar {
pub command: Ustr,
pub args: Vec<Expr>, // alternatives
pub vars: Vec<(Ustr, Expr)>,
}

impl Grammar {
Expand All @@ -28,9 +29,15 @@ impl Grammar {
}

#[derive(Debug, PartialEq)]
struct Variant {
lhs: Ustr,
rhs: Expr,
enum Statement {
CallVariant {
lhs: Ustr,
rhs: Expr,
},
VariableDefinition {
symbol: Ustr,
rhs: Expr,
},
}

// Can't use an arena here until proptest supports non-owned types: https://github.com/proptest-rs/proptest/issues/9
Expand Down Expand Up @@ -174,34 +181,68 @@ fn expr(input: &str) -> IResult<&str, Expr> {
alternative_expr(input)
}

fn variant(input: &str) -> IResult<&str, Variant> {
fn call_variant(input: &str) -> IResult<&str, Statement> {
let (input, name) = terminal(input)?;
let (input, _) = multispace1(input)?;
let (input, expr) = expr(input)?;
let (input, _) = multispace0(input)?;
let (input, _) = char(';')(input)?;
let production = Variant {

let production = Statement::CallVariant {
lhs: ustr(name),
rhs: expr,
};

Ok((input, production))
}

fn grammar(input: &str) -> IResult<&str, Vec<Variant>> {
fn variable_definition(input: &str) -> IResult<&str, Statement> {
let (input, symbol) = symbol(input)?;
let (input, _) = multispace0(input)?;
let (input, _) = tag("::=")(input)?;
let (input, _) = multispace0(input)?;
let (input, e) = expr(input)?;
let (input, _) = multispace0(input)?;
let (input, _) = char(';')(input)?;

let stmt = Statement::VariableDefinition {
symbol: ustr(symbol),
rhs: e,
};

Ok((input, stmt))
}

fn statement(input: &str) -> IResult<&str, Statement> {
let (input, stmt) = alt((call_variant, variable_definition))(input)?;
let (input, _) = multispace0(input)?;
Ok((input, stmt))
}

fn grammar(input: &str) -> IResult<&str, Vec<Statement>> {
let (input, _) = multispace0(input)?;
let (input, variants) = separated_list1(multispace1, variant)(input)?;
let (input, statements) = many0(statement)(input)?;
let (input, _) = multispace0(input)?;
Ok((input, variants))
Ok((input, statements))
}

pub fn parse(input: &str) -> Result<Grammar> {
let (_, variants) = match grammar(input) {
Ok((input, variants)) => (input, variants),
let (input, statements) = match grammar(input) {
Ok((input, statements)) => (input, statements),
Err(e) => return Err(Error::ParsingError(e.to_string())),
};

let mut commands: Vec<Ustr> = variants.iter().map(|v| v.lhs).collect();
commands.sort();
if !input.is_empty() {
return Err(Error::TrailingInput(input.to_owned()));
}

let mut commands: Vec<Ustr> = statements.iter().filter_map(|v|
match v {
Statement::CallVariant { lhs, .. } => Some(*lhs),
Statement::VariableDefinition { .. } => None,
}
).collect();
commands.sort_unstable();
commands.dedup();
if commands.len() > 1 {
return Err(Error::VaryingCommandNames(
Expand All @@ -213,10 +254,24 @@ pub fn parse(input: &str) -> Result<Grammar> {
return Err(Error::EmptyGrammar);
}

let v: Vec<Expr> = variants.into_iter().map(|v| v.rhs).collect();
let call_variants: Vec<Expr> = statements.iter().filter_map(|v|
match v {
Statement::CallVariant { rhs, .. } => Some(rhs.clone()),
Statement::VariableDefinition { .. } => None,
}
).collect();

let variable_definitions: Vec<(Ustr, Expr)> = statements.iter().filter_map(|v|
match v {
Statement::CallVariant { .. } => None,
Statement::VariableDefinition { symbol, rhs } => Some((*symbol, rhs.clone())),
}
).collect();

let g = Grammar {
command: ustr(&commands[0]),
args: v,
args: call_variants,
vars: variable_definitions,
};
Ok(g)
}
Expand Down Expand Up @@ -403,10 +458,10 @@ pub mod tests {
#[test]
fn parses_variant() {
const INPUT: &str = r#"foo bar;"#;
let ("", v) = variant(INPUT).unwrap() else { panic!("parsing error"); };
let ("", v) = call_variant(INPUT).unwrap() else { panic!("parsing error"); };
assert_eq!(
v,
Variant {
Statement::CallVariant {
lhs: u("foo"),
rhs: Expr::Literal(u("bar"))
}
Expand All @@ -425,6 +480,7 @@ foo baz;
Grammar {
command: u("foo"),
args: vec![Expr::Literal(u("bar")), Expr::Literal(u("baz"))],
vars: vec![],
}
);
}
Expand Down Expand Up @@ -452,6 +508,7 @@ foo baz;
]))),
]),
])],
vars: vec![],
},
);
}
Expand Down Expand Up @@ -492,8 +549,29 @@ darcs initialize ( ( --hashed | --darcs-2 | --old-fashioned-inventory ) | --repo
darcs optimize ( --repodir <DIRECTORY> | --reorder-patches | --sibling <URL> | --relink | --relink-pristine | --upgrade | --pristine | ( --compress | --dont-compress | --uncompress ) | --umask <UMASK> | ( --debug | --debug-verbose | --debug-http | ( -v | --verbose ) | ( -q | --quiet ) | --standard-verbosity ) | --timings | ( --posthook <COMMAND> | --no-posthook ) | ( --prompt-posthook | --run-posthook ) | ( --prehook <COMMAND> | --no-prehook ) | ( --prompt-prehook | --run-prehook ) ) ... ;
darcs check ( ( --complete | --partial ) | ( --no-test | --test ) | ( --leave-test-directory | --remove-test-directory ) | --repodir <DIRECTORY> | --ignore-times | ( --debug | --debug-verbose | --debug-http | ( -v | --verbose ) | ( -q | --quiet ) | --standard-verbosity ) | --timings | ( --posthook <COMMAND> | --no-posthook ) | ( --prompt-posthook | --run-posthook ) | ( --prehook <COMMAND> | --no-prehook ) | ( --prompt-prehook | --run-prehook ) ) ... ;
darcs repair ( --repodir <DIRECTORY> | --umask <UMASK> | ( --debug | --debug-verbose | --debug-http | ( -v | --verbose ) | ( -q | --quiet ) | --standard-verbosity ) | --timings | ( --posthook <COMMAND> | --no-posthook ) | ( --prompt-posthook | --run-posthook ) | ( --prehook <COMMAND> | --no-prehook ) | ( --prompt-prehook | --run-prehook ) ) ... ;
darcs convert ( ( --repo-name <DIRECTORY> | --repodir <DIRECTORY> ) | ( --set-scripts-executable | --dont-set-scripts-executable ) | ( --ssh-cm | --no-ssh-cm ) | ( --http-pipelining | --no-http-pipelining ) | --no-cache | ( --debug | --debug-verbose | --debug-http | ( -v | --verbose ) | ( -q | --quiet ) | --standard-verbosity ) | --timings | ( --posthook <COMMAND> | --no-posthook ) | ( --prompt-posthook | --run-posthook ) | ( --prehook <COMMAND> | --no-prehook ) | ( --prompt-prehook | --run-prehook ) ) ... <SOURCE> [<DESTINATION>]
darcs convert ( ( --repo-name <DIRECTORY> | --repodir <DIRECTORY> ) | ( --set-scripts-executable | --dont-set-scripts-executable ) | ( --ssh-cm | --no-ssh-cm ) | ( --http-pipelining | --no-http-pipelining ) | --no-cache | ( --debug | --debug-verbose | --debug-http | ( -v | --verbose ) | ( -q | --quiet ) | --standard-verbosity ) | --timings | ( --posthook <COMMAND> | --no-posthook ) | ( --prompt-posthook | --run-posthook ) | ( --prehook <COMMAND> | --no-prehook ) | ( --prompt-prehook | --run-prehook ) ) ... <SOURCE> [<DESTINATION>];
"#;
let _ = parse(INPUT).unwrap();
}

#[test]
fn parses_variable_definition() {
use Expr::*;
const INPUT: &str = r#"
grep [<OPTION>]... <PATTERNS> [<FILE>]...;
<OPTION> ::= --color <WHEN>;
<WHEN> ::= always | never | auto;
"#;
let g = parse(INPUT).unwrap();
assert_eq!(g.vars, [
(
u("OPTION"),
Sequence(vec![Literal(ustr("--color")), Variable(ustr("WHEN"))]),
),
(
u("WHEN"),
Alternative(vec![Literal(ustr("always")), Literal(ustr("never")), Literal(ustr("auto"))]),
),
]);
}
}
3 changes: 3 additions & 0 deletions src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,9 @@ pub enum Error {
#[error("Empty grammar")]
EmptyGrammar,

#[error("Trailing input")]
TrailingInput(String),

#[error("One one command is allowed in completions definition")]
VaryingCommandNames(Vec<Ustr>),

Expand Down

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