Add PRINTLN_EMPTY_STRING lint.

This commit is contained in:
Malo Jaffré 2017-10-20 16:45:17 +02:00
parent 4d9ed8beef
commit 22f3ca0e2c
4 changed files with 78 additions and 16 deletions

View file

@ -530,6 +530,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry) {
partialeq_ne_impl::PARTIALEQ_NE_IMPL,
precedence::PRECEDENCE,
print::PRINT_WITH_NEWLINE,
print::PRINTLN_EMPTY_STRING,
ptr::CMP_NULL,
ptr::MUT_FROM_REF,
ptr::PTR_ARG,

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@ -1,11 +1,30 @@
use std::ops::Deref;
use rustc::hir::*;
use rustc::hir::map::Node::{NodeImplItem, NodeItem};
use rustc::lint::*;
use syntax::ast::LitKind;
use syntax::symbol::InternedString;
use syntax_pos::Span;
use utils::{is_expn_of, match_def_path, match_path, resolve_node, span_lint};
use utils::{paths, opt_def_id};
/// **What it does:** This lint warns when you using `println!("")` to
/// print a newline.
///
/// **Why is this bad?** You should use `println!()`, which is simpler.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// println!("");
/// ```
declare_lint! {
pub PRINTLN_EMPTY_STRING,
Warn,
"using `print!()` with a format string that ends in a newline"
}
/// **What it does:** This lint warns when you using `print!()` with a format
/// string that
/// ends in a newline.
@ -64,7 +83,7 @@ pub struct Pass;
impl LintPass for Pass {
fn get_lints(&self) -> LintArray {
lint_array!(PRINT_WITH_NEWLINE, PRINT_STDOUT, USE_DEBUG)
lint_array!(PRINT_WITH_NEWLINE, PRINTLN_EMPTY_STRING, PRINT_STDOUT, USE_DEBUG)
}
}
@ -88,10 +107,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
span_lint(cx, PRINT_STDOUT, span, &format!("use of `{}!`", name));
// Check print! with format string ending in "\n".
if_let_chain!{[
name == "print",
// ensure we're calling Arguments::new_v1
args.len() == 1,
let ExprCall(ref args_fun, ref args_args) = args[0].node,
@ -102,20 +118,13 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
let ExprAddrOf(_, ref match_expr) = args_args[1].node,
let ExprMatch(ref args, _, _) = match_expr.node,
let ExprTup(ref args) = args.node,
// collect the format string parts and check the last one
let Some((fmtstr, fmtlen)) = get_argument_fmtstr_parts(&args_args[0]),
let Some('\n') = fmtstr.chars().last(),
// "foo{}bar" is made into two strings + one argument,
// if the format string starts with `{}` (eg. "{}foo"),
// the string array is prepended an empty string "".
// We only want to check the last string after any `{}`:
args.len() < fmtlen,
], {
span_lint(cx, PRINT_WITH_NEWLINE, span,
"using `print!()` with a format string that ends in a \
newline, consider using `println!()` instead");
match name {
"print" => check_print(cx, span, args, fmtstr, fmtlen),
"println" => check_println(cx, span, fmtstr, fmtlen),
_ => (),
}
}}
}
}
@ -135,6 +144,46 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
}
}
// Check for print!("... \n", ...).
fn check_print<'a, 'tcx>(
cx: &LateContext<'a, 'tcx>,
span: Span,
args: &HirVec<Expr>,
fmtstr: InternedString,
fmtlen: usize,
) {
if_let_chain!{[
// check the final format string part
let Some('\n') = fmtstr.chars().last(),
// "foo{}bar" is made into two strings + one argument,
// if the format string starts with `{}` (eg. "{}foo"),
// the string array is prepended an empty string "".
// We only want to check the last string after any `{}`:
args.len() < fmtlen,
], {
span_lint(cx, PRINT_WITH_NEWLINE, span,
"using `print!()` with a format string that ends in a \
newline, consider using `println!()` instead");
}}
}
/// Check for println!("")
fn check_println<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, span: Span, fmtstr: InternedString, fmtlen: usize) {
if_let_chain!{[
// check that the string is empty
fmtlen == 1,
fmtstr.deref() == "\n",
// check the presence of that string
let Ok(snippet) = cx.sess().codemap().span_to_snippet(span),
snippet.contains("\"\""),
], {
span_lint(cx, PRINT_WITH_NEWLINE, span,
"using `println!(\"\")`, consider using `println!()` instead");
}}
}
fn is_in_debug_impl(cx: &LateContext, expr: &Expr) -> bool {
let map = &cx.tcx.hir;

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@ -0,0 +1,4 @@
fn main() {
println!();
println!("");
}

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@ -0,0 +1,8 @@
error: using `println!("")`, consider using `println!()` instead
--> $DIR/println_empty_string.rs:3:5
|
3 | println!("");
| ^^^^^^^^^^^^^
|
= note: `-D print-with-newline` implied by `-D warnings`