Panic on `&&` and `||` operators

bug: Logical operators && and || may panic if not followed by a command.

expect: syntax error.

related: none.

test case#1 code: input

ls &&||

test case#2 code: input

ls &&;

actual: output

[...]
thread 'main' panicked at 'begin <= end (6 <= 5) when slicing `ls &&||`', src/lib/parser/statement/splitter.rs:55:35
stack backtrace:
   [...]
   4: ion_shell::parser::statement::splitter::StatementSplitter::get_statement
   5: <ion_shell::parser::statement::splitter::StatementSplitter as core::iter::traits::iterator::Iterator>::next
   6: ion_shell::shell::flow::<impl ion_shell::shell::Shell>::on_command
   7: ion::binary::InteractiveShell::exec
   8: ion::binary::InteractiveShell::execute_interactive
   9: ion::main
Abandon (core dumped)

expect: output

ion: syntax error: expected command, but found `||`

version: ion 1.0.0-alpha (x86_64-unknown-linux-gnu), rev 814ed5a8

interaction: none

---

According to backtrace, the bug came from src/lib/parser/statement/splitter.rs:55:35 which is :

    fn get_statement(&self, start: usize, end: usize) -> StatementVariant<'a> {
        if self.logical == LogicalOp::And {
            StatementVariant::And(self.data[start + 1..end].trim())
                                            ^^^^^^^^^^^^^^^
        } else if self.logical == LogicalOp::Or {
            StatementVariant::Or(self.data[start + 1..end].trim())
        } else {
            StatementVariant::Default(self.data[start..end].trim())
        }
    }

called by src/lib/parser/statement/splitter.rs:160:42 and src/lib/parser/statement/splitter.rs:171:42 :

                b';' if self.paren_level == 0 => {
                    let statement = self.get_statement(start, i);
                                         ^^^^^^^^^^^^^^^^^^^^^^^
                    self.logical = LogicalOp::None;

                    self.read = i + 1;
                    return match error {
                        Some(error) => Some(Err(error)),
                        None => Some(Ok(statement)),
                    };
                }
                b'&' | b'|' if self.paren_level == 0 && last == Some(character) => {
                    // Detecting if there is a 2nd `&` character
                    let statement = self.get_statement(start, i - 1);
                                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^
                    self.logical = if character == b'&' { LogicalOp::And } else { LogicalOp::Or };
                    self.read = i + 1;
                    return match error {
                        Some(error) => Some(Err(error)),
                        None => Some(Ok(statement)),
                    };
                }
                _ => {}
            }
            last = Some(character);
        }

On both calls, get_statement try to slice the command line with incorrect index.

If we pick test case#1, ls &&||, start equals 5 but is added 1 and i equals 6 minus 1 which gives &"ls &&||"[6..5].

As I understand, syntax is checked along the command execution so a syntax error can be raised while Ion

has already executed N statements from a given command line. Ion could check if self.logical is already

set to And or Or instead of None while performing &&, || or ; but it does not look quite right

and did not pass cargo test(infinity loop) when I tried to implement it.

I'm pretty new to Rust and it feels a bit overwhelming for now to find an elegant solution which does fit well

with Ion's codebase.

Thanks in advance for your help,

Aurélien