Fix output when piping to files

Author: blyxyas

src/driver.rs

@@ -22,6 +22,7 @@ use rustc_session::EarlyErrorHandler;
 use rustc_span::symbol::Symbol;
 
 use std::env;
+use std::io::IsTerminal;
 use std::ops::Deref;
 use std::path::Path;
 use std::process::exit;
@@ -162,8 +163,9 @@ impl rustc_driver::Callbacks for ClippyCallbacks {
     }
 }
 
-fn display_help() {
-    println!("{}", color_print::cstr!(
+fn display_help(is_terminal: bool) {
+    if is_terminal {
+        println!("{}", color_print::cstr!(
 "Checks a package to catch common mistakes and improve your Rust code.
 
 <green,bold>Usage</>:
@@ -191,7 +193,37 @@ You can use tool lints to allow or deny lints from your code, e.g.:
 
     <yellow,bold>#[allow(clippy::needless_lifetimes)]</>
 "
-    ));
+        ));
+    } else {
+        println!(
+            "Checks a package to catch common mistakes and improve your Rust code.
+
+Usage:
+    cargo clippy [OPTIONS] [--] [<ARGS>...]
+
+Common options:
+    --no-deps                Run Clippy only on the given crate, without linting the dependencies
+    --fix                    Automatically apply lint suggestions. This flag implies `--no-deps` and `--all-targets`
+    -h, --help               Print this message
+    -V, --version            Print version info and exit
+    --explain [LINT]           Print the documentation for a given lint
+
+See all options with `cargo check --help`.
+
+Allowing / Denying lints:
+
+To allow or deny a lint from the command line you can use `cargo clippy --` with:
+
+    -W / --warn [LINT]       Set lint warnings
+    -A / --allow [LINT]      Set lint allowed
+    -D / --deny [LINT]       Set lint denied
+    -F / --forbid [LINT]     Set lint forbidden
+
+You can use tool lints to allow or deny lints from your code, e.g.:
+
+    #[allow(clippy::needless_lifetimes)]"
+        );
+    }
 }
 
 const BUG_REPORT_URL: &str = "https://github.com/rust-lang/rust-clippy/issues/new?template=ice.yml";
@@ -252,7 +284,7 @@ pub fn main() {
         }
 
         if !wrapper_mode && (orig_args.iter().any(|a| a == "--help" || a == "-h") || orig_args.len() == 1) {
-            display_help();
+            display_help(std::io::stdout().is_terminal());
             exit(0);
         }
 

src/main.rs

@@ -3,11 +3,13 @@
 #![warn(rust_2018_idioms, unused_lifetimes)]
 
 use std::env;
+use std::io::IsTerminal;
 use std::path::PathBuf;
 use std::process::{self, Command};
 
-fn show_help() {
-    println!("{}", color_print::cstr!(
+fn show_help(is_terminal: bool) {
+    if is_terminal {
+        println!("{}", color_print::cstr!(
 "Checks a package to catch common mistakes and improve your Rust code.
 
 <green,bold>Usage</>:
@@ -35,7 +37,37 @@ You can use tool lints to allow or deny lints from your code, e.g.:
 
     <yellow,bold>#[allow(clippy::needless_lifetimes)]</>
 "
-    ));
+        ));
+    } else {
+        println!(
+            "Checks a package to catch common mistakes and improve your Rust code.
+
+Usage:
+    cargo clippy [OPTIONS] [--] [<ARGS>...]
+
+Common options:
+    --no-deps                Run Clippy only on the given crate, without linting the dependencies
+    --fix                    Automatically apply lint suggestions. This flag implies `--no-deps` and `--all-targets`
+    -h, --help               Print this message
+    -V, --version            Print version info and exit
+    --explain [LINT]           Print the documentation for a given lint
+
+See all options with `cargo check --help`.
+
+Allowing / Denying lints:
+
+To allow or deny a lint from the command line you can use `cargo clippy --` with:
+
+    -W / --warn [LINT]       Set lint warnings
+    -A / --allow [LINT]      Set lint allowed
+    -D / --deny [LINT]       Set lint denied
+    -F / --forbid [LINT]     Set lint forbidden
+
+You can use tool lints to allow or deny lints from your code, e.g.:
+
+    #[allow(clippy::needless_lifetimes)]"
+        );
+    }
 }
 
 fn show_version() {
@@ -44,9 +76,10 @@ fn show_version() {
 }
 
 pub fn main() {
+    let in_terminal = std::io::stdout().is_terminal();
     // Check for version and help flags even when invoked as 'cargo-clippy'
     if env::args().any(|a| a == "--help" || a == "-h") {
-        show_help();
+        show_help(in_terminal);
         return;
     }
 
@@ -62,7 +95,7 @@ pub fn main() {
                 &lint.strip_prefix("clippy::").unwrap_or(&lint).replace('-', "_"),
             ));
         } else {
-            show_help();
+            show_help(in_terminal);
         }
         return;
     }