492 lines
17 KiB
Rust
492 lines
17 KiB
Rust
use std::borrow::Cow;
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use std::ops::Range;
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use crate::utils::{snippet_with_applicability, span_lint, span_lint_and_sugg, span_lint_and_then};
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use rustc_ast::ast::{Expr, ExprKind, Item, ItemKind, MacCall, StrLit, StrStyle};
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use rustc_ast::token;
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use rustc_ast::tokenstream::TokenStream;
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use rustc_errors::Applicability;
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use rustc_lexer::unescape::{self, EscapeError};
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use rustc_lint::{EarlyContext, EarlyLintPass};
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use rustc_parse::parser;
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use rustc_session::{declare_tool_lint, impl_lint_pass};
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use rustc_span::symbol::Symbol;
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use rustc_span::{BytePos, Span};
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declare_clippy_lint! {
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/// **What it does:** This lint warns when you use `println!("")` to
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/// print a newline.
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///
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/// **Why is this bad?** You should use `println!()`, which is simpler.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust
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/// println!("");
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/// ```
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pub PRINTLN_EMPTY_STRING,
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style,
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"using `println!(\"\")` with an empty string"
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}
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declare_clippy_lint! {
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/// **What it does:** This lint warns when you use `print!()` with a format
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/// string that
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/// ends in a newline.
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///
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/// **Why is this bad?** You should use `println!()` instead, which appends the
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/// newline.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust
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/// # let name = "World";
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/// print!("Hello {}!\n", name);
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/// ```
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/// use println!() instead
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/// ```rust
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/// # let name = "World";
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/// println!("Hello {}!", name);
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/// ```
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pub PRINT_WITH_NEWLINE,
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style,
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"using `print!()` with a format string that ends in a single newline"
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}
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declare_clippy_lint! {
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/// **What it does:** Checks for printing on *stdout*. The purpose of this lint
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/// is to catch debugging remnants.
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///
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/// **Why is this bad?** People often print on *stdout* while debugging an
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/// application and might forget to remove those prints afterward.
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///
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/// **Known problems:** Only catches `print!` and `println!` calls.
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///
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/// **Example:**
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/// ```rust
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/// println!("Hello world!");
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/// ```
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pub PRINT_STDOUT,
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restriction,
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"printing on stdout"
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}
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declare_clippy_lint! {
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/// **What it does:** Checks for use of `Debug` formatting. The purpose of this
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/// lint is to catch debugging remnants.
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///
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/// **Why is this bad?** The purpose of the `Debug` trait is to facilitate
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/// debugging Rust code. It should not be used in user-facing output.
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///
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/// **Example:**
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/// ```rust
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/// # let foo = "bar";
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/// println!("{:?}", foo);
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/// ```
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pub USE_DEBUG,
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restriction,
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"use of `Debug`-based formatting"
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}
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declare_clippy_lint! {
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/// **What it does:** This lint warns about the use of literals as `print!`/`println!` args.
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///
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/// **Why is this bad?** Using literals as `println!` args is inefficient
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/// (c.f., https://github.com/matthiaskrgr/rust-str-bench) and unnecessary
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/// (i.e., just put the literal in the format string)
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///
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/// **Known problems:** Will also warn with macro calls as arguments that expand to literals
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/// -- e.g., `println!("{}", env!("FOO"))`.
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///
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/// **Example:**
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/// ```rust
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/// println!("{}", "foo");
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/// ```
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/// use the literal without formatting:
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/// ```rust
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/// println!("foo");
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/// ```
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pub PRINT_LITERAL,
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style,
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"printing a literal with a format string"
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}
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declare_clippy_lint! {
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/// **What it does:** This lint warns when you use `writeln!(buf, "")` to
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/// print a newline.
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///
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/// **Why is this bad?** You should use `writeln!(buf)`, which is simpler.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust
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/// # use std::fmt::Write;
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/// # let mut buf = String::new();
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/// writeln!(buf, "");
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/// ```
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pub WRITELN_EMPTY_STRING,
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style,
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"using `writeln!(buf, \"\")` with an empty string"
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}
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declare_clippy_lint! {
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/// **What it does:** This lint warns when you use `write!()` with a format
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/// string that
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/// ends in a newline.
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///
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/// **Why is this bad?** You should use `writeln!()` instead, which appends the
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/// newline.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust
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/// # use std::fmt::Write;
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/// # let mut buf = String::new();
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/// # let name = "World";
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/// write!(buf, "Hello {}!\n", name);
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/// ```
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pub WRITE_WITH_NEWLINE,
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style,
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"using `write!()` with a format string that ends in a single newline"
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}
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declare_clippy_lint! {
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/// **What it does:** This lint warns about the use of literals as `write!`/`writeln!` args.
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///
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/// **Why is this bad?** Using literals as `writeln!` args is inefficient
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/// (c.f., https://github.com/matthiaskrgr/rust-str-bench) and unnecessary
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/// (i.e., just put the literal in the format string)
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///
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/// **Known problems:** Will also warn with macro calls as arguments that expand to literals
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/// -- e.g., `writeln!(buf, "{}", env!("FOO"))`.
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///
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/// **Example:**
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/// ```rust
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/// # use std::fmt::Write;
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/// # let mut buf = String::new();
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/// writeln!(buf, "{}", "foo");
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/// ```
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pub WRITE_LITERAL,
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style,
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"writing a literal with a format string"
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}
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#[derive(Default)]
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pub struct Write {
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in_debug_impl: bool,
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}
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impl_lint_pass!(Write => [
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PRINT_WITH_NEWLINE,
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PRINTLN_EMPTY_STRING,
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PRINT_STDOUT,
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USE_DEBUG,
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PRINT_LITERAL,
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WRITE_WITH_NEWLINE,
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WRITELN_EMPTY_STRING,
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WRITE_LITERAL
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]);
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impl EarlyLintPass for Write {
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fn check_item(&mut self, _: &EarlyContext<'_>, item: &Item) {
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if let ItemKind::Impl {
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of_trait: Some(trait_ref),
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..
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} = &item.kind
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{
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let trait_name = trait_ref
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.path
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.segments
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.iter()
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.last()
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.expect("path has at least one segment")
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.ident
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.name;
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if trait_name == sym!(Debug) {
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self.in_debug_impl = true;
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}
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}
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}
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fn check_item_post(&mut self, _: &EarlyContext<'_>, _: &Item) {
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self.in_debug_impl = false;
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}
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fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &MacCall) {
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if mac.path == sym!(println) {
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span_lint(cx, PRINT_STDOUT, mac.span(), "use of `println!`");
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if let (Some(fmt_str), _) = self.check_tts(cx, &mac.args.inner_tokens(), false) {
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if fmt_str.symbol == Symbol::intern("") {
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span_lint_and_sugg(
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cx,
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PRINTLN_EMPTY_STRING,
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mac.span(),
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"using `println!(\"\")`",
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"replace it with",
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"println!()".to_string(),
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Applicability::MachineApplicable,
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);
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}
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}
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} else if mac.path == sym!(print) {
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span_lint(cx, PRINT_STDOUT, mac.span(), "use of `print!`");
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if let (Some(fmt_str), _) = self.check_tts(cx, &mac.args.inner_tokens(), false) {
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if check_newlines(&fmt_str) {
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span_lint_and_then(
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cx,
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PRINT_WITH_NEWLINE,
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mac.span(),
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"using `print!()` with a format string that ends in a single newline",
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|err| {
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err.multipart_suggestion(
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"use `println!` instead",
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vec![
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(mac.path.span, String::from("println")),
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(newline_span(&fmt_str), String::new()),
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],
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Applicability::MachineApplicable,
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);
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},
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);
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}
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}
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} else if mac.path == sym!(write) {
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if let (Some(fmt_str), _) = self.check_tts(cx, &mac.args.inner_tokens(), true) {
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if check_newlines(&fmt_str) {
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span_lint_and_then(
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cx,
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WRITE_WITH_NEWLINE,
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mac.span(),
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"using `write!()` with a format string that ends in a single newline",
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|err| {
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err.multipart_suggestion(
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"use `writeln!()` instead",
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vec![
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(mac.path.span, String::from("writeln")),
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(newline_span(&fmt_str), String::new()),
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],
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Applicability::MachineApplicable,
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);
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},
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)
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}
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}
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} else if mac.path == sym!(writeln) {
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if let (Some(fmt_str), expr) = self.check_tts(cx, &mac.args.inner_tokens(), true) {
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if fmt_str.symbol == Symbol::intern("") {
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let mut applicability = Applicability::MachineApplicable;
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let suggestion = expr.map_or_else(
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move || {
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applicability = Applicability::HasPlaceholders;
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Cow::Borrowed("v")
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},
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move |expr| snippet_with_applicability(cx, expr.span, "v", &mut applicability),
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);
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span_lint_and_sugg(
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cx,
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WRITELN_EMPTY_STRING,
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mac.span(),
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format!("using `writeln!({}, \"\")`", suggestion).as_str(),
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"replace it with",
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format!("writeln!({})", suggestion),
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applicability,
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);
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}
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}
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}
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}
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}
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/// Given a format string that ends in a newline and its span, calculates the span of the
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/// newline.
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fn newline_span(fmtstr: &StrLit) -> Span {
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let sp = fmtstr.span;
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let contents = &fmtstr.symbol.as_str();
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let newline_sp_hi = sp.hi()
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- match fmtstr.style {
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StrStyle::Cooked => BytePos(1),
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StrStyle::Raw(hashes) => BytePos((1 + hashes).into()),
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};
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let newline_sp_len = if contents.ends_with('\n') {
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BytePos(1)
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} else if contents.ends_with(r"\n") {
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BytePos(2)
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} else {
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panic!("expected format string to contain a newline");
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};
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sp.with_lo(newline_sp_hi - newline_sp_len).with_hi(newline_sp_hi)
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}
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impl Write {
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/// Checks the arguments of `print[ln]!` and `write[ln]!` calls. It will return a tuple of two
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/// `Option`s. The first `Option` of the tuple is the macro's format string. It includes
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/// the contents of the string, whether it's a raw string, and the span of the literal in the
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/// source. The second `Option` in the tuple is, in the `write[ln]!` case, the expression the
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/// `format_str` should be written to.
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///
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/// Example:
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///
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/// Calling this function on
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/// ```rust
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/// # use std::fmt::Write;
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/// # let mut buf = String::new();
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/// # let something = "something";
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/// writeln!(buf, "string to write: {}", something);
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/// ```
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/// will return
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/// ```rust,ignore
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/// (Some("string to write: {}"), Some(buf))
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/// ```
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#[allow(clippy::too_many_lines)]
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fn check_tts<'a>(
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&self,
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cx: &EarlyContext<'a>,
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tts: &TokenStream,
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is_write: bool,
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) -> (Option<StrLit>, Option<Expr>) {
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use fmt_macros::{
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AlignUnknown, ArgumentImplicitlyIs, ArgumentIs, ArgumentNamed, CountImplied, FormatSpec, Parser, Piece,
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};
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let tts = tts.clone();
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let mut parser = parser::Parser::new(&cx.sess.parse_sess, tts, false, None);
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let mut expr: Option<Expr> = None;
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if is_write {
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expr = match parser.parse_expr().map_err(|mut err| err.cancel()) {
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Ok(p) => Some(p.into_inner()),
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Err(_) => return (None, None),
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};
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// might be `writeln!(foo)`
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if parser.expect(&token::Comma).map_err(|mut err| err.cancel()).is_err() {
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return (None, expr);
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}
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}
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let fmtstr = match parser.parse_str_lit() {
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Ok(fmtstr) => fmtstr,
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Err(_) => return (None, expr),
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};
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let tmp = fmtstr.symbol.as_str();
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let mut args = vec![];
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let mut fmt_parser = Parser::new(&tmp, None, Vec::new(), false);
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while let Some(piece) = fmt_parser.next() {
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if !fmt_parser.errors.is_empty() {
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return (None, expr);
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}
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if let Piece::NextArgument(arg) = piece {
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if !self.in_debug_impl && arg.format.ty == "?" {
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// FIXME: modify rustc's fmt string parser to give us the current span
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span_lint(cx, USE_DEBUG, parser.prev_token.span, "use of `Debug`-based formatting");
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}
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args.push(arg);
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}
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}
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let lint = if is_write { WRITE_LITERAL } else { PRINT_LITERAL };
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let mut idx = 0;
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loop {
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const SIMPLE: FormatSpec<'_> = FormatSpec {
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fill: None,
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align: AlignUnknown,
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flags: 0,
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precision: CountImplied,
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precision_span: None,
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width: CountImplied,
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width_span: None,
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ty: "",
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ty_span: None,
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};
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if !parser.eat(&token::Comma) {
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return (Some(fmtstr), expr);
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}
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let token_expr = if let Ok(expr) = parser.parse_expr().map_err(|mut err| err.cancel()) {
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expr
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} else {
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return (Some(fmtstr), None);
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};
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match &token_expr.kind {
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ExprKind::Lit(_) => {
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let mut all_simple = true;
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let mut seen = false;
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for arg in &args {
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match arg.position {
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ArgumentImplicitlyIs(n) | ArgumentIs(n) => {
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if n == idx {
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all_simple &= arg.format == SIMPLE;
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seen = true;
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}
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},
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ArgumentNamed(_) => {},
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}
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}
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if all_simple && seen {
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span_lint(cx, lint, token_expr.span, "literal with an empty format string");
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}
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idx += 1;
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},
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ExprKind::Assign(lhs, rhs, _) => {
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if let ExprKind::Lit(_) = rhs.kind {
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if let ExprKind::Path(_, p) = &lhs.kind {
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let mut all_simple = true;
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let mut seen = false;
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for arg in &args {
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match arg.position {
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ArgumentImplicitlyIs(_) | ArgumentIs(_) => {},
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ArgumentNamed(name) => {
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if *p == name {
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seen = true;
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all_simple &= arg.format == SIMPLE;
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}
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},
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}
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}
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if all_simple && seen {
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span_lint(cx, lint, rhs.span, "literal with an empty format string");
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}
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}
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}
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},
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_ => idx += 1,
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}
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}
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}
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}
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|
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/// Checks if the format string contains a single newline that terminates it.
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///
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/// Literal and escaped newlines are both checked (only literal for raw strings).
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fn check_newlines(fmtstr: &StrLit) -> bool {
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let mut has_internal_newline = false;
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let mut last_was_cr = false;
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let mut should_lint = false;
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let contents = &fmtstr.symbol.as_str();
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let mut cb = |r: Range<usize>, c: Result<char, EscapeError>| {
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let c = c.unwrap();
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if r.end == contents.len() && c == '\n' && !last_was_cr && !has_internal_newline {
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should_lint = true;
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} else {
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last_was_cr = c == '\r';
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if c == '\n' {
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has_internal_newline = true;
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}
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}
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};
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match fmtstr.style {
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StrStyle::Cooked => unescape::unescape_literal(contents, unescape::Mode::Str, &mut cb),
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StrStyle::Raw(_) => unescape::unescape_literal(contents, unescape::Mode::RawStr, &mut cb),
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}
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should_lint
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}
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