Update parser tests with env var

Author: matklad

crates/ra_syntax/test_data/parser/inline/err/0009_attr_on_expr_not_allowed.rast

@@ -56,4 +56,3 @@ SOURCE_FILE@0..48
       R_CURLY@46..47 "}"
   WHITESPACE@47..48 "\n"
 error 24..24: attributes are not allowed on BIN_EXPR
-error 44..44: attributes are not allowed on IF_EXPR

crates/test_utils/src/lib.rs

@@ -10,17 +10,17 @@
 pub mod mark;
 
 use std::{
-    fs,
+    env, fs,
     path::{Path, PathBuf},
 };
 
-pub use ra_cfg::CfgOptions;
+use serde_json::Value;
 use stdx::split1;
+use text_size::{TextRange, TextSize};
 
+pub use ra_cfg::CfgOptions;
 pub use relative_path::{RelativePath, RelativePathBuf};
 pub use rustc_hash::FxHashMap;
-use serde_json::Value;
-use text_size::{TextRange, TextSize};
 
 pub use difference::Changeset as __Changeset;
 
@@ -625,8 +625,6 @@ pub fn skip_slow_tests() -> bool {
     should_skip
 }
 
-const REWRITE: bool = false;
-
 /// Asserts that `expected` and `actual` strings are equal. If they differ only
 /// in trailing or leading whitespace the test won't fail and
 /// the contents of `actual` will be written to the file located at `path`.
@@ -642,7 +640,7 @@ fn assert_equal_text(expected: &str, actual: &str, path: &Path) {
         fs::write(path, actual).unwrap();
         return;
     }
-    if REWRITE {
+    if env::var("UPDATE_EXPECTATIONS").is_ok() {
         println!("rewriting {}", pretty_path.display());
         fs::write(path, actual).unwrap();
         return;

docs/dev/README.md

@@ -342,6 +342,12 @@ There are two kinds of tests:
 The purpose of inline tests is not to achieve full coverage by test cases, but to explain to the reader of the code what each particular `if` and `match` is responsible for.
 If you are tempted to add a large inline test, it might be a good idea to leave only the simplest example in place, and move the test to a manual `parser/ok` test.
 
+To update test data, run with `UPDATE_EXPECTATIONS` variable:
+
+```bash
+env UPDATE_EXPECTATIONS=1 cargo qt
+```
+
 # Logging
 
 Logging is done by both rust-analyzer and VS Code, so it might be tricky to