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test: Remplaced panic in favor of ParseError

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This commit is contained in:
leon3s 2023-03-19 18:58:11 +01:00
parent 23289e66d2
commit 9fb18bb08c
1 changed files with 74 additions and 48 deletions
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122
src/uu/test/src/parser.rs
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@ -11,7 +11,6 @@ use std::ffi::OsString;
use std::iter::Peekable;
use uucore::display::Quotable;
use uucore::show_error;
/// Represents one of the binary comparison operators for strings, integers, or files
#[derive(Debug, PartialEq, Eq)]
@ -40,6 +39,25 @@ pub enum Symbol {
None,
}
/// Represents an error encountered while parsing a test expression
pub enum ParseError {
MissingArgument(OsString),
Expected(OsString),
}
/// A Result type for parsing test expressions
type ParseResult<T> = Result<T, ParseError>;
/// Display an error message for a ParseError
impl std::fmt::Display for ParseError {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
match self {
Self::Expected(s) => write!(f, "expected {}", s.to_string_lossy()),
Self::MissingArgument(s) => write!(f, "missing argument for {}", s.to_string_lossy()),
}
}
}
impl Symbol {
/// Create a new Symbol from an OsString.
///
@ -133,16 +151,10 @@ impl Parser {
}
/// Consume the next token & verify that it matches the provided value.
///
/// # Panics
///
/// Panics if the next token does not match the provided value.
///
/// TODO: remove panics and convert Parser to return error messages.
fn expect(&mut self, value: &str) {
fn expect(&mut self, value: &str) -> ParseResult<()> {
match self.next_token() {
Symbol::Literal(s) if s == value => (),
_ => panic!("expected ‘{value}’"),
Symbol::Literal(s) if s == value => Ok(()),
_ => Err(ParseError::Expected(value.into())),
}
}
@ -162,25 +174,27 @@ impl Parser {
/// Parse an expression.
///
/// EXPR → TERM | EXPR BOOLOP EXPR
fn expr(&mut self) {
fn expr(&mut self) -> ParseResult<()> {
if !self.peek_is_boolop() {
self.term();
self.term()?;
}
self.maybe_boolop();
self.maybe_boolop()?;
Ok(())
}
/// Parse a term token and possible subsequent symbols: "(", "!", UOP,
/// literal, or None.
fn term(&mut self) {
fn term(&mut self) -> ParseResult<()> {
let symbol = self.next_token();
match symbol {
Symbol::LParen => self.lparen(),
Symbol::Bang => self.bang(),
Symbol::LParen => self.lparen()?,
Symbol::Bang => self.bang()?,
Symbol::UnaryOp(_) => self.uop(symbol),
Symbol::None => self.stack.push(symbol),
literal => self.literal(literal),
literal => self.literal(literal)?,
}
Ok(())
}
/// Parse a (possibly) parenthesized expression.
@ -192,7 +206,7 @@ impl Parser {
/// * when followed by a binary operator that is not _itself_ interpreted
/// as a literal
///
fn lparen(&mut self) {
fn lparen(&mut self) -> ParseResult<()> {
// Look ahead up to 3 tokens to determine if the lparen is being used
// as a grouping operator or should be treated as a literal string
let peek3: Vec<Symbol> = self
@ -204,13 +218,13 @@ impl Parser {
match peek3.as_slice() {
// case 1: lparen is a literal when followed by nothing
[] => self.literal(Symbol::LParen.into_literal()),
[] => {
self.literal(Symbol::LParen.into_literal())?;
Ok(())
}
// case 2: error if end of stream is `( <any_token>`
[symbol] => {
show_error!("missing argument after ‘{:?}’", symbol);
std::process::exit(2);
}
[symbol] => Err(ParseError::MissingArgument(format!("{symbol:#?}").into())),
// case 3: `( uop <any_token> )` → parenthesized unary operation;
// this case ensures we don’t get confused by `( -f ) )`
@ -218,43 +232,49 @@ impl Parser {
[Symbol::UnaryOp(_), _, Symbol::Literal(s)] if s == ")" => {
let symbol = self.next_token();
self.uop(symbol);
self.expect(")");
self.expect(")")?;
Ok(())
}
// case 4: binary comparison of literal lparen, e.g. `( != )`
[Symbol::Op(_), Symbol::Literal(s)] | [Symbol::Op(_), Symbol::Literal(s), _]
if s == ")" =>
{
self.literal(Symbol::LParen.into_literal());
self.literal(Symbol::LParen.into_literal())?;
Ok(())
}
// case 5: after handling the prior cases, any single token inside
// parentheses is a literal, e.g. `( -f )`
[_, Symbol::Literal(s)] | [_, Symbol::Literal(s), _] if s == ")" => {
let symbol = self.next_token();
self.literal(symbol);
self.expect(")");
self.literal(symbol)?;
self.expect(")")?;
Ok(())
}
// case 6: two binary ops in a row, treat the first op as a literal
[Symbol::Op(_), Symbol::Op(_), _] => {
let symbol = self.next_token();
self.literal(symbol);
self.expect(")");
self.literal(symbol)?;
self.expect(")")?;
Ok(())
}
// case 7: if earlier cases didn’t match, `( op <any_token>…`
// indicates binary comparison of literal lparen with
// anything _except_ ")" (case 4)
[Symbol::Op(_), _] | [Symbol::Op(_), _, _] => {
self.literal(Symbol::LParen.into_literal());
self.literal(Symbol::LParen.into_literal())?;
Ok(())
}
// Otherwise, lparen indicates the start of a parenthesized
// expression
_ => {
self.expr();
self.expect(")");
self.expr()?;
self.expect(")")?;
Ok(())
}
}
}
@ -276,7 +296,7 @@ impl Parser {
/// * `! str BOOLOP str`: negate the entire Boolean expression
/// * `! str BOOLOP EXPR BOOLOP EXPR`: negate the value of the first `str` term
///
fn bang(&mut self) {
fn bang(&mut self) -> ParseResult<()> {
match self.peek() {
Symbol::Op(_) | Symbol::BoolOp(_) => {
// we need to peek ahead one more token to disambiguate the first
@ -289,14 +309,14 @@ impl Parser {
Symbol::Op(_) | Symbol::None => {
// op is literal
let op = self.next_token().into_literal();
self.literal(op);
self.literal(op)?;
self.stack.push(Symbol::Bang);
}
// case 2: `<! as literal> OP str [BOOLOP EXPR]`.
_ => {
// bang is literal; parsing continues with op
self.literal(Symbol::Bang.into_literal());
self.maybe_boolop();
self.literal(Symbol::Bang.into_literal())?;
self.maybe_boolop()?;
}
}
}
@ -317,32 +337,34 @@ impl Parser {
match peek4.as_slice() {
// we peeked ahead 4 but there were only 3 tokens left
[Symbol::Literal(_), Symbol::BoolOp(_), Symbol::Literal(_)] => {
self.expr();
self.expr()?;
self.stack.push(Symbol::Bang);
}
_ => {
self.term();
self.term()?;
self.stack.push(Symbol::Bang);
}
}
}
}
Ok(())
}
/// Peek at the next token and parse it as a BOOLOP or string literal,
/// as appropriate.
fn maybe_boolop(&mut self) {
fn maybe_boolop(&mut self) -> ParseResult<()> {
if self.peek_is_boolop() {
let symbol = self.next_token();
// BoolOp by itself interpreted as Literal
if let Symbol::None = self.peek() {
self.literal(symbol.into_literal());
self.literal(symbol.into_literal())?;
} else {
self.boolop(symbol);
self.maybe_boolop();
self.boolop(symbol)?;
self.maybe_boolop()?;
}
}
Ok(())
}
/// Parse a Boolean expression.
@ -350,13 +372,14 @@ impl Parser {
/// Logical and (-a) has higher precedence than or (-o), so in an
/// expression like `foo -o '' -a ''`, the and subexpression is evaluated
/// first.
fn boolop(&mut self, op: Symbol) {
fn boolop(&mut self, op: Symbol) -> ParseResult<()> {
if op == Symbol::BoolOp(OsString::from("-a")) {
self.term();
self.term()?;
} else {
self.expr();
self.expr()?;
}
self.stack.push(op);
Ok(())
}
/// Parse a (possible) unary argument test (string length or file
@ -375,7 +398,7 @@ impl Parser {
/// Parse a string literal, optionally followed by a comparison operator
/// and a second string literal.
fn literal(&mut self, token: Symbol) {
fn literal(&mut self, token: Symbol) -> ParseResult<()> {
self.stack.push(token.into_literal());
// EXPR → str OP str
@ -383,18 +406,21 @@ impl Parser {
let op = self.next_token();
match self.next_token() {
Symbol::None => panic!("missing argument after {op:?}"),
Symbol::None => {
return Err(ParseError::MissingArgument(format!("{op:#?}").into()));
}
token => self.stack.push(token.into_literal()),
}
self.stack.push(op);
}
Ok(())
}
/// Parser entry point: parse the token stream `self.tokens`, storing the
/// resulting `Symbol` stack in `self.stack`.
fn parse(&mut self) -> Result<(), String> {
self.expr();
self.expr().map_err(|e| e.to_string())?;
match self.tokens.next() {
Some(token) => Err(format!("extra argument {}", token.quote())),