Auto merge of #9865 - nyurik:allow-mixed, r=xFrednet

Add allow-mixed-uninlined-format-args config

Implement `allow-mixed-uninlined-format-args` config param to change the behavior of the `uninlined_format_args` lint. Now it is a part of `style` per [Zulip chat](https://rust-lang.zulipchat.com/#narrow/stream/257328-clippy/topic/.60uninlined_format_args.60.20category), and won't propose inlining in case of a mixed usage, e.g. `print!("{} {}", var, 1+2)`. If the user sets `allow-mixed-uninlined-format-args` config param to `false`, the lint would behave like it did before -- proposing to inline args even in the mixed case.

---

changelog: [`uninlined_format_args`]: Added a new config `allow-mixed-uninlined-format-args` to allow the lint, if only some arguments can be inlined
[#9865](#9865)
changelog: Moved [`uninlined_format_args`] to `style` (Now warn-by-default)
[#9865](#9865)

clippy_lints/src/format_args.rs

@@ -1,6 +1,6 @@
 use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_and_then};
 use clippy_utils::is_diag_trait_item;
-use clippy_utils::macros::FormatParamKind::{Implicit, Named, Numbered, Starred};
+use clippy_utils::macros::FormatParamKind::{Implicit, Named, NamedInline, Numbered, Starred};
 use clippy_utils::macros::{
     is_format_macro, is_panic, root_macro_call, Count, FormatArg, FormatArgsExpn, FormatParam, FormatParamUsage,
 };
@@ -106,19 +106,25 @@ declare_clippy_lint! {
     /// format!("{var:.prec$}");
     /// ```
     ///
-    /// ### Known Problems
-    ///
-    /// There may be a false positive if the format string is expanded from certain proc macros:
-    ///
-    /// ```ignore
-    /// println!(indoc!("{}"), var);
+    /// If allow-mixed-uninlined-format-args is set to false in clippy.toml,
+    /// the following code will also trigger the lint:
+    /// ```rust
+    /// # let var = 42;
+    /// format!("{} {}", var, 1+2);
+    /// ```
+    /// Use instead:
+    /// ```rust
+    /// # let var = 42;
+    /// format!("{var} {}", 1+2);
     /// ```
     ///
+    /// ### Known Problems
+    ///
     /// If a format string contains a numbered argument that cannot be inlined
     /// nothing will be suggested, e.g. `println!("{0}={1}", var, 1+2)`.
     #[clippy::version = "1.65.0"]
     pub UNINLINED_FORMAT_ARGS,
-    pedantic,
+    style,
     "using non-inlined variables in `format!` calls"
 }
 
@@ -162,12 +168,16 @@ impl_lint_pass!(FormatArgs => [
 
 pub struct FormatArgs {
     msrv: Msrv,
+    ignore_mixed: bool,
 }
 
 impl FormatArgs {
     #[must_use]
-    pub fn new(msrv: Msrv) -> Self {
-        Self { msrv }
+    pub fn new(msrv: Msrv, allow_mixed_uninlined_format_args: bool) -> Self {
+        Self {
+            msrv,
+            ignore_mixed: allow_mixed_uninlined_format_args,
+        }
     }
 }
 
@@ -192,7 +202,7 @@ impl<'tcx> LateLintPass<'tcx> for FormatArgs {
                 check_to_string_in_format_args(cx, name, arg.param.value);
             }
             if self.msrv.meets(msrvs::FORMAT_ARGS_CAPTURE) {
-                check_uninlined_args(cx, &format_args, outermost_expn_data.call_site, macro_def_id);
+                check_uninlined_args(cx, &format_args, outermost_expn_data.call_site, macro_def_id, self.ignore_mixed);
             }
         }
     }
@@ -270,7 +280,13 @@ fn check_unused_format_specifier(cx: &LateContext<'_>, arg: &FormatArg<'_>) {
     }
 }
 
-fn check_uninlined_args(cx: &LateContext<'_>, args: &FormatArgsExpn<'_>, call_site: Span, def_id: DefId) {
+fn check_uninlined_args(
+    cx: &LateContext<'_>,
+    args: &FormatArgsExpn<'_>,
+    call_site: Span,
+    def_id: DefId,
+    ignore_mixed: bool,
+) {
     if args.format_string.span.from_expansion() {
         return;
     }
@@ -285,7 +301,7 @@ fn check_uninlined_args(cx: &LateContext<'_>, args: &FormatArgsExpn<'_>, call_si
     // we cannot remove any other arguments in the format string,
     // because the index numbers might be wrong after inlining.
     // Example of an un-inlinable format:  print!("{}{1}", foo, 2)
-    if !args.params().all(|p| check_one_arg(args, &p, &mut fixes)) || fixes.is_empty() {
+    if !args.params().all(|p| check_one_arg(args, &p, &mut fixes, ignore_mixed)) || fixes.is_empty() {
         return;
     }
 
@@ -309,7 +325,12 @@ fn check_uninlined_args(cx: &LateContext<'_>, args: &FormatArgsExpn<'_>, call_si
     );
 }
 
-fn check_one_arg(args: &FormatArgsExpn<'_>, param: &FormatParam<'_>, fixes: &mut Vec<(Span, String)>) -> bool {
+fn check_one_arg(
+    args: &FormatArgsExpn<'_>,
+    param: &FormatParam<'_>,
+    fixes: &mut Vec<(Span, String)>,
+    ignore_mixed: bool,
+) -> bool {
     if matches!(param.kind, Implicit | Starred | Named(_) | Numbered)
         && let ExprKind::Path(QPath::Resolved(None, path)) = param.value.kind
         && let [segment] = path.segments
@@ -324,8 +345,10 @@ fn check_one_arg(args: &FormatArgsExpn<'_>, param: &FormatParam<'_>, fixes: &mut
         fixes.push((arg_span, String::new()));
         true  // successful inlining, continue checking
     } else {
-        // if we can't inline a numbered argument, we can't continue
-        param.kind != Numbered
+        // Do not continue inlining (return false) in case
+        // * if we can't inline a numbered argument, e.g. `print!("{0} ...", foo.bar, ...)`
+        // * if allow_mixed_uninlined_format_args is false and this arg hasn't been inlined already
+        param.kind != Numbered && (!ignore_mixed || matches!(param.kind, NamedInline(_)))
     }
 }
 

clippy_lints/src/lib.rs

@@ -828,7 +828,8 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         ))
     });
     store.register_late_pass(move |_| Box::new(undocumented_unsafe_blocks::UndocumentedUnsafeBlocks));
-    store.register_late_pass(move |_| Box::new(format_args::FormatArgs::new(msrv())));
+    let allow_mixed_uninlined = conf.allow_mixed_uninlined_format_args;
+    store.register_late_pass(move |_| Box::new(format_args::FormatArgs::new(msrv(), allow_mixed_uninlined)));
     store.register_late_pass(|_| Box::new(trailing_empty_array::TrailingEmptyArray));
     store.register_early_pass(|| Box::new(octal_escapes::OctalEscapes));
     store.register_late_pass(|_| Box::new(needless_late_init::NeedlessLateInit));

clippy_lints/src/utils/conf.rs

@@ -402,6 +402,10 @@ define_Conf! {
     /// A list of paths to types that should be treated like `Arc`, i.e. ignored but
     /// for the generic parameters for determining interior mutability
     (ignore_interior_mutability: Vec<String> = Vec::from(["bytes::Bytes".into()])),
+    /// Lint: UNINLINED_FORMAT_ARGS.
+    ///
+    /// Whether to allow mixed uninlined format args, e.g. `format!("{} {}", a, foo.bar)`
+    (allow_mixed_uninlined_format_args: bool = true),
 }
 
 /// Search for the configuration file.

tests/ui-toml/allow_mixed_uninlined_format_args/clippy.toml

@@ -0,0 +1 @@
+allow-mixed-uninlined-format-args = false

tests/ui-toml/allow_mixed_uninlined_format_args/uninlined_format_args.fixed

@@ -0,0 +1,14 @@
+// run-rustfix
+#![warn(clippy::uninlined_format_args)]
+
+fn main() {
+    let local_i32 = 1;
+    let local_f64 = 2.0;
+    let local_opt: Option<i32> = Some(3);
+
+    println!("val='{local_i32}'");
+    println!("Hello x is {local_f64:.local_i32$}");
+    println!("Hello {local_i32} is {local_f64:.*}", 5);
+    println!("Hello {local_i32} is {local_f64:.*}", 5);
+    println!("{local_i32}, {}", local_opt.unwrap());
+}

tests/ui-toml/allow_mixed_uninlined_format_args/uninlined_format_args.rs

@@ -0,0 +1,14 @@
+// run-rustfix
+#![warn(clippy::uninlined_format_args)]
+
+fn main() {
+    let local_i32 = 1;
+    let local_f64 = 2.0;
+    let local_opt: Option<i32> = Some(3);
+
+    println!("val='{}'", local_i32);
+    println!("Hello {} is {:.*}", "x", local_i32, local_f64);
+    println!("Hello {} is {:.*}", local_i32, 5, local_f64);
+    println!("Hello {} is {2:.*}", local_i32, 5, local_f64);
+    println!("{}, {}", local_i32, local_opt.unwrap());
+}

tests/ui-toml/allow_mixed_uninlined_format_args/uninlined_format_args.stderr

@@ -0,0 +1,76 @@
+error: variables can be used directly in the `format!` string
+  --> $DIR/uninlined_format_args.rs:9:5
+   |
+LL |     println!("val='{}'", local_i32);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `-D clippy::uninlined-format-args` implied by `-D warnings`
+help: change this to
+   |
+LL -     println!("val='{}'", local_i32);
+LL +     println!("val='{local_i32}'");
+   |
+
+error: literal with an empty format string
+  --> $DIR/uninlined_format_args.rs:10:35
+   |
+LL |     println!("Hello {} is {:.*}", "x", local_i32, local_f64);
+   |                                   ^^^
+   |
+   = note: `-D clippy::print-literal` implied by `-D warnings`
+help: try this
+   |
+LL -     println!("Hello {} is {:.*}", "x", local_i32, local_f64);
+LL +     println!("Hello x is {:.*}", local_i32, local_f64);
+   |
+
+error: variables can be used directly in the `format!` string
+  --> $DIR/uninlined_format_args.rs:10:5
+   |
+LL |     println!("Hello {} is {:.*}", "x", local_i32, local_f64);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: change this to
+   |
+LL -     println!("Hello {} is {:.*}", "x", local_i32, local_f64);
+LL +     println!("Hello {} is {local_f64:.local_i32$}", "x");
+   |
+
+error: variables can be used directly in the `format!` string
+  --> $DIR/uninlined_format_args.rs:11:5
+   |
+LL |     println!("Hello {} is {:.*}", local_i32, 5, local_f64);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: change this to
+   |
+LL -     println!("Hello {} is {:.*}", local_i32, 5, local_f64);
+LL +     println!("Hello {local_i32} is {local_f64:.*}", 5);
+   |
+
+error: variables can be used directly in the `format!` string
+  --> $DIR/uninlined_format_args.rs:12:5
+   |
+LL |     println!("Hello {} is {2:.*}", local_i32, 5, local_f64);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: change this to
+   |
+LL -     println!("Hello {} is {2:.*}", local_i32, 5, local_f64);
+LL +     println!("Hello {local_i32} is {local_f64:.*}", 5);
+   |
+
+error: variables can be used directly in the `format!` string
+  --> $DIR/uninlined_format_args.rs:13:5
+   |
+LL |     println!("{}, {}", local_i32, local_opt.unwrap());
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: change this to
+   |
+LL -     println!("{}, {}", local_i32, local_opt.unwrap());
+LL +     println!("{local_i32}, {}", local_opt.unwrap());
+   |
+
+error: aborting due to 6 previous errors
+

tests/ui-toml/toml_unknown_key/conf_unknown_key.stderr

@@ -1,6 +1,7 @@
 error: error reading Clippy's configuration file `$DIR/clippy.toml`: unknown field `foobar`, expected one of
            allow-dbg-in-tests
            allow-expect-in-tests
+           allow-mixed-uninlined-format-args
            allow-print-in-tests
            allow-unwrap-in-tests
            allowed-scripts

tests/ui/uninlined_format_args.fixed

@@ -54,11 +54,11 @@ fn tester(fn_arg: i32) {
     println!("{local_i32:<3}");
     println!("{local_i32:#010x}");
     println!("{local_f64:.1}");
-    println!("Hello {} is {local_f64:.local_i32$}", "x");
-    println!("Hello {local_i32} is {local_f64:.*}", 5);
-    println!("Hello {local_i32} is {local_f64:.*}", 5);
+    println!("Hello {} is {:.*}", "x", local_i32, local_f64);
+    println!("Hello {} is {:.*}", local_i32, 5, local_f64);
+    println!("Hello {} is {2:.*}", local_i32, 5, local_f64);
     println!("{local_i32} {local_f64}");
-    println!("{local_i32}, {}", local_opt.unwrap());
+    println!("{}, {}", local_i32, local_opt.unwrap());
     println!("{val}");
     println!("{val}");
     println!("{} {1}", local_i32, 42);

tests/ui/uninlined_format_args.stderr

@@ -177,42 +177,6 @@ LL -     println!("{:.1}", local_f64);
 LL +     println!("{local_f64:.1}");
    |
 
-error: variables can be used directly in the `format!` string
-  --> $DIR/uninlined_format_args.rs:59:5
-   |
-LL |     println!("Hello {} is {:.*}", "x", local_i32, local_f64);
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-help: change this to
-   |
-LL -     println!("Hello {} is {:.*}", "x", local_i32, local_f64);
-LL +     println!("Hello {} is {local_f64:.local_i32$}", "x");
-   |
-
-error: variables can be used directly in the `format!` string
-  --> $DIR/uninlined_format_args.rs:60:5
-   |
-LL |     println!("Hello {} is {:.*}", local_i32, 5, local_f64);
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-help: change this to
-   |
-LL -     println!("Hello {} is {:.*}", local_i32, 5, local_f64);
-LL +     println!("Hello {local_i32} is {local_f64:.*}", 5);
-   |
-
-error: variables can be used directly in the `format!` string
-  --> $DIR/uninlined_format_args.rs:61:5
-   |
-LL |     println!("Hello {} is {2:.*}", local_i32, 5, local_f64);
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-help: change this to
-   |
-LL -     println!("Hello {} is {2:.*}", local_i32, 5, local_f64);
-LL +     println!("Hello {local_i32} is {local_f64:.*}", 5);
-   |
-
 error: variables can be used directly in the `format!` string
   --> $DIR/uninlined_format_args.rs:62:5
    |
@@ -225,18 +189,6 @@ LL -     println!("{} {}", local_i32, local_f64);
 LL +     println!("{local_i32} {local_f64}");
    |
 
-error: variables can be used directly in the `format!` string
-  --> $DIR/uninlined_format_args.rs:63:5
-   |
-LL |     println!("{}, {}", local_i32, local_opt.unwrap());
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-   |
-help: change this to
-   |
-LL -     println!("{}, {}", local_i32, local_opt.unwrap());
-LL +     println!("{local_i32}, {}", local_opt.unwrap());
-   |
-
 error: variables can be used directly in the `format!` string
   --> $DIR/uninlined_format_args.rs:64:5
    |
@@ -904,5 +856,5 @@ LL -     println!("expand='{}'", local_i32);
 LL +     println!("expand='{local_i32}'");
    |
 
-error: aborting due to 76 previous errors
+error: aborting due to 72 previous errors