feat: conditionally allow unstable opts on stable/beta

.github/workflows/integration.yml

@@ -15,10 +15,7 @@ jobs:
       matrix:
         integration: [
           bitflags,
-          chalk,
-          crater,
           error-chain,
-          glob,
           log,
           mdbook,
           packed_simd,
@@ -37,6 +34,15 @@ jobs:
           # Instead, leverage `continue-on-error`
           # https://help.github.com/en/actions/automating-your-workflow-with-github-actions/workflow-syntax-for-github-actions#jobsjob_idstepscontinue-on-error
           #
+          # Failing due to breaking changes in rustfmt 2.0 where empty
+          # match blocks have trailing commas removed
+          # https://github.com/rust-lang/rustfmt/pull/4226
+          - integration: chalk
+            allow-failure: true
+          - integration: crater
+            allow-failure: true
+          - integration: glob
+            allow-failure: true
           # Using old rustfmt configuration option
           - integration: rand
             allow-failure: true

.travis.yml

@@ -18,10 +18,7 @@ matrix:
     - env: CFG_RELEASE_CHANNEL=beta
     - os: osx
     - env: INTEGRATION=bitflags
-    - env: INTEGRATION=chalk
-    - env: INTEGRATION=crater
     - env: INTEGRATION=error-chain
-    - env: INTEGRATION=glob
     - env: INTEGRATION=log
     - env: INTEGRATION=mdbook
     - env: INTEGRATION=packed_simd
@@ -30,6 +27,12 @@ matrix:
     - env: INTEGRATION=tempdir
     - env: INTEGRATION=futures-rs
   allow_failures:
+    # Failing due to breaking changes in rustfmt 2.0 where empty
+    # match blocks have trailing commas removed
+    # https://github.com/rust-lang/rustfmt/pull/4226
+    - env: INTEGRATION=chalk
+    - env: INTEGRATION=crater
+    - env: INTEGRATION=glob
     # Using old configuration option
     - env: INTEGRATION=rand
     # Doesn't build - keep this in allow_failures as it's fragile to breaking changes of rustc.

Configurations.md

@@ -2395,11 +2395,18 @@ fn lorem<Ipsum: Dolor+Sit=Amet>() {
 
 ## `unstable_features`
 
-Enable unstable features on the unstable channel.
+Enable unstable features on stable and beta channels (unstable features are available by default on nightly).
 
 - **Default value**: `false`
 - **Possible values**: `true`, `false`
-- **Stable**: No (tracking issue: [#3387](https://github.com/rust-lang/rustfmt/issues/3387))
+- **Stable**: Yes
+
+**Note** - if you are setting unstable configuration options via the CLI instead of the configuration file, then you should include a `unstable_features=true` item before any of the unstable items.
+
+For example:
+```bash
+rustfmt src/lib.rs --config unstable_features=true merge_imports=true
+```
 
 ## `use_field_init_shorthand`
 

src/config.rs

@@ -142,8 +142,9 @@ create_config! {
     // Control options (changes the operation of rustfmt, rather than the formatting)
     required_version: String, env!("CARGO_PKG_VERSION").to_owned(), false,
         "Require a specific version of rustfmt";
-    unstable_features: bool, false, false,
-            "Enables unstable features. Only available on nightly channel";
+    unstable_features: bool, false, true,
+            "Enables unstable features on stable and beta channels (unstable features are enabled \
+             by default on nightly channel)";
     hide_parse_errors: bool, false, false, "Hide errors from the parser";
     error_on_line_overflow: bool, false, false, "Error if unable to get all lines within max_width";
     error_on_unformatted: bool, false, false,
@@ -437,6 +438,10 @@ mod test {
             single_line_if_else_max_width: usize, 50, true, "Maximum line length for single \
                 line if-else expressions. A value of zero means always break if-else expressions.";
 
+            unstable_features: bool, false, true,
+                "Enables unstable features on stable and beta channels (unstable features are enabled \
+                 by default on nightly channel)";
+
             // Options that are used by the tests
             stable_option: bool, false, true, "A stable option";
             unstable_option: bool, false, false, "An unstable option";
@@ -693,13 +698,31 @@ ignore = []
         }
 
         #[test]
-        fn test_from_toml_not_nightly() {
+        fn test_from_toml_not_nightly_unstable_set() {
             if is_nightly_channel!() {
                 // This test requires non-nightly
                 return;
             }
-            let config = Config::from_toml("unstable_features = true", Path::new("")).unwrap();
-            assert_eq!(config.was_set().unstable_features(), false);
+            let toml = r#"
+                unstable_features = true
+                merge_imports = true
+            "#;
+            let config = Config::from_toml(toml, Path::new("")).unwrap();
+            assert_eq!(config.was_set().unstable_features(), true);
+            assert_eq!(config.was_set().merge_imports(), true);
+            assert_eq!(config.unstable_features(), true);
+            assert_eq!(config.merge_imports(), true);
+        }
+
+        #[test]
+        fn test_from_toml_not_nightly_unstable_not_set() {
+            if is_nightly_channel!() {
+                // This test requires non-nightly
+                return;
+            }
+            let config = Config::from_toml("merge_imports = true", Path::new("")).unwrap();
+            assert_eq!(config.was_set().merge_imports(), false);
+            assert_eq!(config.merge_imports(), false);
         }
 
         #[test]
@@ -744,8 +767,12 @@ ignore = []
             }
             let mut config = Config::default();
             assert_eq!(config.unstable_features(), false);
+            config.override_value("merge_imports", "true");
+            assert_eq!(config.merge_imports(), false);
             config.override_value("unstable_features", "true");
             assert_eq!(config.unstable_features(), true);
+            config.override_value("merge_imports", "true");
+            assert_eq!(config.merge_imports(), true);
         }
 
         #[test]

src/config/config_type.rs

@@ -167,11 +167,14 @@ macro_rules! create_config {
                     if self.$i.3 {
                         update_config!(self, $i = val, dir);
                     } else {
-                        if is_nightly_channel!() {
+                        if parsed.unstable_features == Some(true) || is_nightly_channel!() {
                             update_config!(self, $i = val, dir);
                         } else {
-                            eprintln!("Warning: can't set `{} = {:?}`, unstable features are only \
-                                       available in nightly channel.", stringify!($i), val);
+                            eprintln!(
+                                "Warning: can't set `{} = {:?}`, unstable features can only \
+                                be used on stable or beta when `unstable_features` is also enabled.",
+                                stringify!($i), val
+                            );
                         }
                     }
                 }
@@ -237,12 +240,20 @@ macro_rules! create_config {
                 match key {
                     $(
                         stringify!($i) => {
-                            self.$i.1 = true;
-                            self.$i.2 = val.parse::<$Ty>()
+                            if self.$i.3 || self.unstable_features() || is_nightly_channel!() {
+                                self.$i.1 = true;
+                                self.$i.2 = val.parse::<$Ty>()
                                 .expect(&format!("Failed to parse override for {} (\"{}\") as a {}",
                                                  stringify!($i),
                                                  val,
                                                  stringify!($Ty)));
+                            } else {
+                                return eprintln!(
+                                    "Warning: can't set `{} = {:?}`, unstable features can only \
+                                    be used on stable or beta when `unstable_features` is also enabled.",
+                                    stringify!($i), val
+                                );
+                            }
                         }
                     )+
                     _ => panic!("Unknown config key in override: {}", key)

src/test/configuration_snippet.rs

@@ -96,6 +96,9 @@ impl ConfigCodeBlock {
 
     fn get_block_config(&self) -> Config {
         let mut config = Config::default();
+        if !crate::is_nightly_channel!() {
+            config.override_value("unstable_features", "true");
+        }
         if self.config_name.is_some() && self.config_value.is_some() {
             config.override_value(
                 self.config_name.as_ref().unwrap(),

src/test/mod.rs

@@ -629,6 +629,10 @@ fn read_config(filename: &Path) -> (Config, OperationSetting, EmitterConfig) {
         get_config(filename.with_extension("toml").file_name().map(Path::new))
     };
 
+    if !config.was_set().unstable_features() && !is_nightly_channel!() {
+        config.override_value("unstable_features", "true");
+    }
+
     let mut operation_setting = OperationSetting::default();
     let mut emitter_config = EmitterConfig::default();
     for (key, val) in &sig_comments {

tests/config/small_tabs.toml

@@ -1,3 +1,4 @@
+unstable_features = true
 max_width = 100
 comment_width = 80
 tab_spaces = 2