Auto merge of #3946 - rchaser53:issue-3920, r=flip1995

[rust.git] / clippy_lints / src / explicit_write.rs

diff --git a/clippy_lints/src/explicit_write.rs b/clippy_lints/src/explicit_write.rs
index 77c6c1a4ad715edb70450cbd9926ff9822d73e86..64ba3efedc5e2543b4abb6eec9cd7c11a6433055 100644 (file)
--- a/clippy_lints/src/explicit_write.rs
+++ b/clippy_lints/src/explicit_write.rs
@@ -1,27 +1,27 @@
+use crate::utils::{is_expn_of, match_def_path, resolve_node, span_lint, span_lint_and_sugg};
+use if_chain::if_chain;
 use rustc::hir::*;
 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
 use rustc::{declare_tool_lint, lint_array};
-use if_chain::if_chain;
-use crate::utils::{is_expn_of, match_def_path, resolve_node, span_lint};
-use crate::utils::opt_def_id;
+use rustc_errors::Applicability;
+use syntax::ast::LitKind;
 
-/// **What it does:** Checks for usage of `write!()` / `writeln()!` which can be
-/// replaced with `(e)print!()` / `(e)println!()`
-///
-/// **Why is this bad?** Using `(e)println! is clearer and more concise
-///
-/// **Known problems:** None.
-///
-/// **Example:**
-/// ```rust
-/// // this would be clearer as `eprintln!("foo: {:?}", bar);`
-/// writeln!(&mut io::stderr(), "foo: {:?}", bar).unwrap();
-/// ```
 declare_clippy_lint! {
+    /// **What it does:** Checks for usage of `write!()` / `writeln()!` which can be
+    /// replaced with `(e)print!()` / `(e)println!()`
+    ///
+    /// **Why is this bad?** Using `(e)println! is clearer and more concise
+    ///
+    /// **Known problems:** None.
+    ///
+    /// **Example:**
+    /// ```rust
+    /// // this would be clearer as `eprintln!("foo: {:?}", bar);`
+    /// writeln!(&mut io::stderr(), "foo: {:?}", bar).unwrap();
+    /// ```
     pub EXPLICIT_WRITE,
     complexity,
-    "using the `write!()` family of functions instead of the `print!()` family \
-     of functions, when using the latter would work"
+    "using the `write!()` family of functions instead of the `print!()` family of functions, when using the latter would work"
 }
 
 #[derive(Copy, Clone, Debug)]
@@ -31,6 +31,10 @@ impl LintPass for Pass {
     fn get_lints(&self) -> LintArray {
         lint_array!(EXPLICIT_WRITE)
     }
+
+    fn name(&self) -> &'static str {
+        "ExplicitWrite"
+    }
 }
 
 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
@@ -49,7 +53,7 @@ fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
             if let ExprKind::Call(ref dest_fun, _) = write_args[0].node;
             if let ExprKind::Path(ref qpath) = dest_fun.node;
             if let Some(dest_fun_id) =
-                opt_def_id(resolve_node(cx, qpath, dest_fun.hir_id));
+                resolve_node(cx, qpath, dest_fun.hir_id).opt_def_id();
             if let Some(dest_name) = if match_def_path(cx.tcx, dest_fun_id, &["std", "io", "stdio", "stdout"]) {
                 Some("stdout")
             } else if match_def_path(cx.tcx, dest_fun_id, &["std", "io", "stdio", "stderr"]) {
@@ -73,32 +77,85 @@ fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
                 } else {
                     ""
                 };
-                if let Some(macro_name) = calling_macro {
-                    span_lint(
-                        cx,
-                        EXPLICIT_WRITE,
-                        expr.span,
-                        &format!(
-                            "use of `{}!({}(), ...).unwrap()`. Consider using `{}{}!` instead",
-                            macro_name,
-                            dest_name,
-                            prefix,
-                            macro_name.replace("write", "print")
-                        )
-                    );
+
+                // We need to remove the last trailing newline from the string because the
+                // underlying `fmt::write` function doesn't know whether `println!` or `print!` was
+                // used.
+                if let Some(mut write_output) = write_output_string(write_args) {
+                    if write_output.ends_with('\n') {
+                        write_output.pop();
+                    }
+
+                    if let Some(macro_name) = calling_macro {
+                        span_lint_and_sugg(
+                            cx,
+                            EXPLICIT_WRITE,
+                            expr.span,
+                            &format!(
+                                "use of `{}!({}(), ...).unwrap()`",
+                                macro_name,
+                                dest_name
+                            ),
+                            "try this",
+                            format!("{}{}!(\"{}\")", prefix, macro_name.replace("write", "print"), write_output.escape_default()),
+                            Applicability::MachineApplicable
+                        );
+                    } else {
+                        span_lint_and_sugg(
+                            cx,
+                            EXPLICIT_WRITE,
+                            expr.span,
+                            &format!("use of `{}().write_fmt(...).unwrap()`", dest_name),
+                            "try this",
+                            format!("{}print!(\"{}\")", prefix, write_output.escape_default()),
+                            Applicability::MachineApplicable
+                        );
+                    }
                 } else {
-                    span_lint(
-                        cx,
-                        EXPLICIT_WRITE,
-                        expr.span,
-                        &format!(
-                            "use of `{}().write_fmt(...).unwrap()`. Consider using `{}print!` instead",
-                            dest_name,
-                            prefix,
-                        )
-                    );
+                    // We don't have a proper suggestion
+                    if let Some(macro_name) = calling_macro {
+                        span_lint(
+                            cx,
+                            EXPLICIT_WRITE,
+                            expr.span,
+                            &format!(
+                                "use of `{}!({}(), ...).unwrap()`. Consider using `{}{}!` instead",
+                                macro_name,
+                                dest_name,
+                                prefix,
+                                macro_name.replace("write", "print")
+                            )
+                        );
+                    } else {
+                        span_lint(
+                            cx,
+                            EXPLICIT_WRITE,
+                            expr.span,
+                            &format!("use of `{}().write_fmt(...).unwrap()`. Consider using `{}print!` instead", dest_name, prefix),
+                        );
+                    }
                 }
+
             }
         }
     }
 }
+
+// Extract the output string from the given `write_args`.
+fn write_output_string(write_args: &HirVec<Expr>) -> Option<String> {
+    if_chain! {
+        // Obtain the string that should be printed
+        if write_args.len() > 1;
+        if let ExprKind::Call(_, ref output_args) = write_args[1].node;
+        if output_args.len() > 0;
+        if let ExprKind::AddrOf(_, ref output_string_expr) = output_args[0].node;
+        if let ExprKind::Array(ref string_exprs) = output_string_expr.node;
+        if string_exprs.len() > 0;
+        if let ExprKind::Lit(ref lit) = string_exprs[0].node;
+        if let LitKind::Str(ref write_output, _) = lit.node;
+        then {
+            return Some(write_output.to_string())
+        }
+    }
+    None
+}