Rollup merge of rust-lang#48449 - petrochenkov:uidiff, r=nikomatsakis

Anonymize some line numbers in UI test output

New unstable flag `-Z ui-testing` is introduced. This flag changes diagnostic output of the compiler *in some way* making it more suitable for UI testing (this is intentionally vague).
At the moment this flag anonymizes line numbers at line starts thus solving the largest issue with UI test diffs. If diffs continue to be too noisy, some other tweaks could be applied (e.g. anonymizing lines/columns in `--> $DIR/file.rs:line:column`), but this needs some time and experience (we shouldn't diverge too much from the actual output in general).

If comment `// disable-ui-testing-normalization` is added to an UI test, then `-Z ui-testing` is not passed.

Closes rust-lang#46643

src/librustc/session/config.rs

@@ -1322,6 +1322,8 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
          epoch). Crates compiled with different epochs can be linked together."),
     run_dsymutil: Option<bool> = (None, parse_opt_bool, [TRACKED],
           "run `dsymutil` and delete intermediate object files"),
+    ui_testing: bool = (false, parse_bool, [UNTRACKED],
+          "format compiler diagnostics in a way that's better suitable for UI testing"),
 }
 
 pub fn default_lib_output() -> CrateType {

src/librustc/session/mod.rs

@@ -919,11 +919,13 @@ pub fn build_session_with_codemap(sopts: config::Options,
         }
         (config::ErrorOutputType::Json(pretty), None) => {
             Box::new(JsonEmitter::stderr(Some(registry), codemap.clone(),
-                     pretty, sopts.debugging_opts.approximate_suggestions))
+                     pretty, sopts.debugging_opts.approximate_suggestions)
+                     .ui_testing(sopts.debugging_opts.ui_testing))
         }
         (config::ErrorOutputType::Json(pretty), Some(dst)) => {
             Box::new(JsonEmitter::new(dst, Some(registry), codemap.clone(),
-                     pretty, sopts.debugging_opts.approximate_suggestions))
+                     pretty, sopts.debugging_opts.approximate_suggestions)
+                     .ui_testing(sopts.debugging_opts.ui_testing))
         }
         (config::ErrorOutputType::Short(color_config), None) => {
             Box::new(EmitterWriter::stderr(color_config, Some(codemap.clone()), true, false))

src/librustc_errors/emitter.rs

@@ -25,6 +25,8 @@ use std::collections::HashMap;
 use std::cmp::min;
 use unicode_width;
 
+const ANONYMIZED_LINE_NUM: &str = "LL";
+
 /// Emitter trait for emitting errors.
 pub trait Emitter {
     /// Emit a structured diagnostic.
@@ -107,6 +109,7 @@ pub struct EmitterWriter {
     cm: Option<Rc<CodeMapper>>,
     short_message: bool,
     teach: bool,
+    ui_testing: bool,
 }
 
 struct FileWithAnnotatedLines {
@@ -128,13 +131,15 @@ impl EmitterWriter {
                 cm: code_map,
                 short_message,
                 teach,
+                ui_testing: false,
             }
         } else {
             EmitterWriter {
                 dst: Raw(Box::new(io::stderr())),
                 cm: code_map,
                 short_message,
                 teach,
+                ui_testing: false,
             }
         }
     }
@@ -149,6 +154,19 @@ impl EmitterWriter {
             cm: code_map,
             short_message,
             teach,
+            ui_testing: false,
+        }
+    }
+
+    pub fn ui_testing(self, ui_testing: bool) -> Self {
+        Self { ui_testing, ..self }
+    }
+
+    fn maybe_anonymized(&self, line_num: usize) -> String {
+        if self.ui_testing {
+            ANONYMIZED_LINE_NUM.to_string()
+        } else {
+            line_num.to_string()
         }
     }
 
@@ -305,7 +323,7 @@ impl EmitterWriter {
         buffer.puts(line_offset, code_offset, &source_string, Style::Quotation);
         buffer.puts(line_offset,
                     0,
-                    &(line.line_index.to_string()),
+                    &self.maybe_anonymized(line.line_index),
                     Style::LineNumber);
 
         draw_col_separator(buffer, line_offset, width_offset - 2);
@@ -1126,8 +1144,8 @@ impl EmitterWriter {
 
                             buffer.puts(last_buffer_line_num,
                                         0,
-                                        &(annotated_file.lines[line_idx + 1].line_index - 1)
-                                            .to_string(),
+                                        &self.maybe_anonymized(annotated_file.lines[line_idx + 1]
+                                                                             .line_index - 1),
                                         Style::LineNumber);
                             draw_col_separator(&mut buffer,
                                                last_buffer_line_num,
@@ -1201,7 +1219,7 @@ impl EmitterWriter {
                     // Print the span column to avoid confusion
                     buffer.puts(row_num,
                                 0,
-                                &((line_start + line_pos).to_string()),
+                                &self.maybe_anonymized(line_start + line_pos),
                                 Style::LineNumber);
                     // print the suggestion
                     draw_col_separator(&mut buffer, row_num, max_line_num_len + 1);
@@ -1253,8 +1271,11 @@ impl EmitterWriter {
                              span: &MultiSpan,
                              children: &Vec<SubDiagnostic>,
                              suggestions: &[CodeSuggestion]) {
-        let max_line_num = self.get_max_line_num(span, children);
-        let max_line_num_len = max_line_num.to_string().len();
+        let max_line_num_len = if self.ui_testing {
+            ANONYMIZED_LINE_NUM.len()
+        } else {
+            self.get_max_line_num(span, children).to_string().len()
+        };
 
         match self.emit_message_default(span,
                                         message,

src/libsyntax/json.rs

@@ -40,6 +40,7 @@ pub struct JsonEmitter {
     pretty: bool,
     /// Whether "approximate suggestions" are enabled in the config
     approximate_suggestions: bool,
+    ui_testing: bool,
 }
 
 impl JsonEmitter {
@@ -53,6 +54,7 @@ impl JsonEmitter {
             cm: code_map,
             pretty,
             approximate_suggestions,
+            ui_testing: false,
         }
     }
 
@@ -73,8 +75,13 @@ impl JsonEmitter {
             cm: code_map,
             pretty,
             approximate_suggestions,
+            ui_testing: false,
         }
     }
+
+    pub fn ui_testing(self, ui_testing: bool) -> Self {
+        Self { ui_testing, ..self }
+    }
 }
 
 impl Emitter for JsonEmitter {
@@ -199,7 +206,8 @@ impl Diagnostic {
         }
         let buf = BufWriter::default();
         let output = buf.clone();
-        EmitterWriter::new(Box::new(buf), Some(je.cm.clone()), false, false).emit(db);
+        EmitterWriter::new(Box::new(buf), Some(je.cm.clone()), false, false)
+            .ui_testing(je.ui_testing).emit(db);
         let output = Arc::try_unwrap(output.0).unwrap().into_inner().unwrap();
         let output = String::from_utf8(output).unwrap();
 

src/test/ui-fulldeps/custom-derive/issue-36935.stderr

@@ -1,7 +1,7 @@
 error: proc-macro derive panicked
   --> $DIR/issue-36935.rs:18:15
    |
-18 | #[derive(Foo, Bar)] //~ ERROR proc-macro derive panicked
+LL | #[derive(Foo, Bar)] //~ ERROR proc-macro derive panicked
    |               ^^^
    |
    = help: message: lolnope

src/test/ui-fulldeps/deprecated-derive.stderr

@@ -1,6 +1,6 @@
 warning: derive(Encodable) is deprecated in favor of derive(RustcEncodable)
   --> $DIR/deprecated-derive.rs:18:10
    |
-18 | #[derive(Encodable)]
+LL | #[derive(Encodable)]
    |          ^^^^^^^^^
 

src/test/ui-fulldeps/lint-group-plugin.stderr

@@ -1,15 +1,15 @@
 warning: item is named 'lintme'
   --> $DIR/lint-group-plugin.rs:18:1
    |
-18 | fn lintme() { } //~ WARNING item is named 'lintme'
+LL | fn lintme() { } //~ WARNING item is named 'lintme'
    | ^^^^^^^^^^^^^^^
    |
    = note: #[warn(test_lint)] on by default
 
 warning: item is named 'pleaselintme'
   --> $DIR/lint-group-plugin.rs:19:1
    |
-19 | fn pleaselintme() { } //~ WARNING item is named 'pleaselintme'
+LL | fn pleaselintme() { } //~ WARNING item is named 'pleaselintme'
    | ^^^^^^^^^^^^^^^^^^^^^
    |
    = note: #[warn(please_lint)] on by default

src/test/ui-fulldeps/lint-plugin-cmdline-allow.stderr

@@ -1,13 +1,13 @@
 warning: function is never used: `lintme`
   --> $DIR/lint-plugin-cmdline-allow.rs:20:1
    |
-20 | fn lintme() { }
+LL | fn lintme() { }
    | ^^^^^^^^^^^
    |
 note: lint level defined here
   --> $DIR/lint-plugin-cmdline-allow.rs:17:9
    |
-17 | #![warn(unused)]
+LL | #![warn(unused)]
    |         ^^^^^^
    = note: #[warn(dead_code)] implied by #[warn(unused)]
 

src/test/ui-fulldeps/lint-plugin-cmdline-load.stderr

@@ -1,7 +1,7 @@
 warning: item is named 'lintme'
   --> $DIR/lint-plugin-cmdline-load.rs:18:1
    |
-18 | fn lintme() { } //~ WARNING item is named 'lintme'
+LL | fn lintme() { } //~ WARNING item is named 'lintme'
    | ^^^^^^^^^^^^^^^
    |
    = note: #[warn(test_lint)] on by default

src/test/ui-fulldeps/lint-plugin-forbid-attrs.stderr

@@ -1,22 +1,22 @@
 error: item is named 'lintme'
   --> $DIR/lint-plugin-forbid-attrs.rs:18:1
    |
-18 | fn lintme() { } //~ ERROR item is named 'lintme'
+LL | fn lintme() { } //~ ERROR item is named 'lintme'
    | ^^^^^^^^^^^^^^^
    |
 note: lint level defined here
   --> $DIR/lint-plugin-forbid-attrs.rs:16:11
    |
-16 | #![forbid(test_lint)]
+LL | #![forbid(test_lint)]
    |           ^^^^^^^^^
 
 error[E0453]: allow(test_lint) overruled by outer forbid(test_lint)
   --> $DIR/lint-plugin-forbid-attrs.rs:20:9
    |
-16 | #![forbid(test_lint)]
+LL | #![forbid(test_lint)]
    |           --------- `forbid` level set here
 ...
-20 | #[allow(test_lint)]
+LL | #[allow(test_lint)]
    |         ^^^^^^^^^ overruled by previous forbid
 
 error: aborting due to 2 previous errors

src/test/ui-fulldeps/lint-plugin.stderr

@@ -1,7 +1,7 @@
 warning: item is named 'lintme'
   --> $DIR/lint-plugin.rs:18:1
    |
-18 | fn lintme() { } //~ WARNING item is named 'lintme'
+LL | fn lintme() { } //~ WARNING item is named 'lintme'
    | ^^^^^^^^^^^^^^^
    |
    = note: #[warn(test_lint)] on by default