Anonymize some line numbers in UI test output

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

@@ -909,21 +909,24 @@ pub fn build_session_with_codemap(sopts: config::Options,
 
     let emitter: Box<Emitter> = match (sopts.error_format, emitter_dest) {
         (config::ErrorOutputType::HumanReadable(color_config), None) => {
-            Box::new(EmitterWriter::stderr(color_config,
-                                           Some(codemap.clone()),
-                                           false,
-                                           sopts.debugging_opts.teach))
+            Box::new(EmitterWriter::stderr(color_config, Some(codemap.clone()),
+                     false, sopts.debugging_opts.teach)
+                     .ui_testing(sopts.debugging_opts.ui_testing))
         }
         (config::ErrorOutputType::HumanReadable(_), Some(dst)) => {
-            Box::new(EmitterWriter::new(dst, Some(codemap.clone()), false, false))
+            Box::new(EmitterWriter::new(dst, Some(codemap.clone()),
+                     false, false)
+                     .ui_testing(sopts.debugging_opts.ui_testing))
         }
         (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, HashSet};
 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.
@@ -108,6 +110,7 @@ pub struct EmitterWriter {
     short_message: bool,
     teach: bool,
     error_codes: HashSet<String>,
+    ui_testing: bool,
 }
 
 struct FileWithAnnotatedLines {
@@ -157,6 +160,7 @@ impl EmitterWriter {
                 short_message,
                 teach,
                 error_codes: HashSet::new(),
+                ui_testing: false,
             }
         } else {
             EmitterWriter {
@@ -165,6 +169,7 @@ impl EmitterWriter {
                 short_message,
                 teach,
                 error_codes: HashSet::new(),
+                ui_testing: false,
             }
         }
     }
@@ -180,6 +185,20 @@ impl EmitterWriter {
             short_message,
             teach,
             error_codes: HashSet::new(),
+            ui_testing: false,
+        }
+    }
+
+    pub fn ui_testing(mut self, ui_testing: bool) -> Self {
+        self.ui_testing = 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()
         }
     }
 
@@ -336,7 +355,7 @@ 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);
@@ -1159,8 +1178,8 @@ 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,
@@ -1235,7 +1254,7 @@ 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);
@@ -1288,8 +1307,11 @@ 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

src/test/ui-fulldeps/proc-macro/load-panic.stderr

@@ -1,7 +1,7 @@
 error: proc-macro derive panicked
   --> $DIR/load-panic.rs:17:10
    |
-17 | #[derive(A)]
+LL | #[derive(A)]
    |          ^
    |
    = help: message: nope!