Clippy lint · Restriction · checked with Clippy 0.1.99

clippy::verbose_file_reads: Checks for usage of File::read_to_end and File::read_to_string

What it meansChecks for usage of File::read_to_end and File::read_to_string. It is in the restriction group and off by default.

Does it matter?

fs::{read, read_to_string} provide the same functionality when buf is empty with fewer imports and no intermediate values. See also: fs::read docs, fs::read_to_string docs

Lints that forbid language features for specific codebases (no unwrap, no indexing...). Off by default; pick them one by one, never the whole group.

How to fix it

Clippy does not fix this one automatically. Change the code by hand:

Flagged

let mut f = File::open("foo.txt").unwrap();
let mut bytes = Vec::new();
f.read_to_end(&mut bytes).unwrap();

Write this instead

let mut bytes = fs::read("foo.txt").unwrap();

Turn it off, or on

It is off by default. To use it, set it to warn or deny:

Whole crate (Cargo.toml)

[lints.clippy]
verbose_file_reads = "warn"

In code

#![warn(clippy::verbose_file_reads)]

One run

cargo clippy -- -W clippy::verbose-file-reads

The [lints] table needs Rust 1.74 or newer. In a workspace, put it under [workspace.lints.clippy] and add [lints] workspace = true to each member.

Restrictiongroup

allowdefault level

nofixed by cargo clippy --fix

1.44.0added in Rust

Clippy's own documentation

What it does

Checks for usage of File::read_to_end and File::read_to_string.

Why restrict this?

fs::{read, read_to_string} provide the same functionality when buf is empty with fewer imports and no intermediate values. See also: fs::read docs, fs::read_to_string docs

Example

let mut f = File::open("foo.txt").unwrap();
let mut bytes = Vec::new();
f.read_to_end(&mut bytes).unwrap();

Can be written more concisely as

let mut bytes = fs::read("foo.txt").unwrap();

From the Clippy lint list (0.1.99), part of the Rust project, MIT or Apache-2.0. Official entry.

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