Add suspicious_command_arg_space lint.

clippy_lints/src/methods/mod.rs

@@ -80,6 +80,7 @@
 mod stable_sort_primitive;
 mod str_splitn;
 mod string_extend_chars;
+mod suspicious_command_arg_space;
 mod suspicious_map;
 mod suspicious_splitn;
 mod suspicious_to_owned;
@@ -3162,6 +3163,32 @@
     "collecting an iterator when collect is not needed"
 }
 
+declare_clippy_lint! {
+    /// ### What it does
+    ///
+    /// Checks for `Command::arg()` invocations that look like they
+    /// should be multiple arguments instead, such as `arg("-t ext2")`.
+    ///
+    /// ### Why is this bad?
+    ///
+    /// Arguments are not split by space. An argument like `arg("-t ext2")`
+    /// will be passed as a single argument to the command,
+    /// which is likely not what was intended.
+    ///
+    /// ### Example
+    /// ```rust
+    /// std::process::Command::new("echo").arg("-n hello").spawn().unwrap();
+    /// ```
+    /// Use instead:
+    /// ```rust
+    /// std::process::Command::new("echo").args(["-n", "hello"]).spawn().unwrap();
+    /// ```
+    #[clippy::version = "1.67.0"]
+    pub SUSPICIOUS_COMMAND_ARG_SPACE,
+    suspicious,
+    "single command line argument that looks like it should be multiple arguments"
+}
+
 pub struct Methods {
     avoid_breaking_exported_api: bool,
     msrv: Msrv,
@@ -3496,6 +3523,9 @@ fn check_methods<'tcx>(&self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
                         unnecessary_lazy_eval::check(cx, expr, recv, arg, "and");
                     }
                 },
+                ("arg", [arg]) => {
+                    suspicious_command_arg_space::check(cx, recv, arg, span);
+                }
                 ("as_deref" | "as_deref_mut", []) => {
                     needless_option_as_deref::check(cx, expr, recv, name);
                 },

clippy_lints/src/methods/suspicious_command_arg_space.rs

@@ -0,0 +1,39 @@
+use clippy_utils::diagnostics::span_lint_and_then;
+use clippy_utils::paths;
+use clippy_utils::ty::match_type;
+use rustc_ast as ast;
+use rustc_errors::{Applicability, Diagnostic};
+use rustc_hir as hir;
+use rustc_lint::LateContext;
+use rustc_span::Span;
+
+use super::SUSPICIOUS_COMMAND_ARG_SPACE;
+
+pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, recv: &'tcx hir::Expr<'_>, arg: &'tcx hir::Expr<'_>, span: Span) {
+    let ty = cx.typeck_results().expr_ty(recv).peel_refs();
+
+    if match_type(cx, ty, &paths::STD_PROCESS_COMMAND)
+        && let hir::ExprKind::Lit(lit) = &arg.kind
+        && let ast::LitKind::Str(s, _) = &lit.node
+        && let Some((arg1, arg2)) = s.as_str().split_once(' ')
+        && arg1.starts_with('-')
+        && arg1.chars().all(|c| c.is_ascii_alphanumeric() || c == '_' || c == '-')
+    {
+        span_lint_and_then(
+            cx,
+            SUSPICIOUS_COMMAND_ARG_SPACE,
+            arg.span,
+            "single argument that looks like it should be multiple arguments",
+            |diag: &mut Diagnostic| {
+                diag.multipart_suggestion_verbose(
+                    "consider splitting the argument",
+                    vec![
+                        (span, "args".to_string()),
+                        (arg.span, format!("[{arg1:?}, {arg2:?}]")),
+                    ],
+                    Applicability::MaybeIncorrect,
+                );
+            }
+        );
+    }
+}

clippy_utils/src/paths.rs

@@ -115,6 +115,7 @@
 pub const STD_IO_SEEK: [&str; 3] = ["std", "io", "Seek"];
 pub const STD_IO_SEEK_FROM_CURRENT: [&str; 4] = ["std", "io", "SeekFrom", "Current"];
 pub const STD_IO_SEEKFROM_START: [&str; 4] = ["std", "io", "SeekFrom", "Start"];
+pub const STD_PROCESS_COMMAND: [&str; 3] = ["std", "process", "Command"];
 pub const STRING_AS_MUT_STR: [&str; 4] = ["alloc", "string", "String", "as_mut_str"];
 pub const STRING_AS_STR: [&str; 4] = ["alloc", "string", "String", "as_str"];
 pub const STRING_NEW: [&str; 4] = ["alloc", "string", "String", "new"];