Allow overriding is_enabled property via config for trait linters

Summary:
# Context

For linters based on [traits](https://whatsapp.github.io/erlang-language-platform/docs/contributing/linters/linter-traits/) we can customize their behaviour via config. Here we extend the configuration mechanism we already use for `severity` and other properties to the `is_enabled` flag. This mechanism will eventually supersede the `enabled_lints` and `disabled_lints` [configuration properties](https://whatsapp.github.io/erlang-language-platform/docs/get-started/configure-project/elp-lint-toml/#enabled_lints).

# Why having a new way to enable and disable linters?

Currently, the `.elp_lint.toml` allows users to specify which linters are enabled or disabled. But the configuration file works in a very counter-intuitive way: say a linter is "disabled by default". To enable it, a user cannot simply add it to the `enabled_list`, since that would cause **only that linter** to run. A user would need to add all available linters to the config, which is clearly not a maintainable solution.

By supporting an override mechanism, it will be possible to - for example - have the following configuration:

```
[linters.my_linter]
enabled = true
```

Which would keep the *enabled* status for all other linters to their default value, ensuring `my_linter` is enabled.

# This diff

This diff introduces the new overriding mechanism. We still keep it undocumented, until all linters are migrated to use a trait.

Reviewed By: TheGeorge

Differential Revision: D85055745

fbshipit-source-id: f84d203c380a45dcbafae5d09dc9141d42a12e91

Author: robertoaloi

crates/ide/src/diagnostics.rs

@@ -550,6 +550,17 @@ fn should_run(
     is_generated: bool,
     is_test: bool,
 ) -> bool {
+    let is_enabled = if let Some(lint_config) = config.lint_config.as_ref() {
+        lint_config
+            .get_is_enabled_override(&linter.id())
+            .unwrap_or_else(|| linter.is_enabled())
+    } else {
+        linter.is_enabled()
+    };
+    if !is_enabled {
+        return false;
+    }
+
     let include_tests = if let Some(lint_config) = config.lint_config.as_ref() {
         lint_config
             .get_include_tests_override(&linter.id())
@@ -1129,6 +1140,11 @@ impl DiagnosticsConfig {
 }
 
 impl LintConfig {
+    /// Get the is_enabled override for a linter based on its diagnostic code
+    pub fn get_is_enabled_override(&self, diagnostic_code: &DiagnosticCode) -> Option<bool> {
+        self.linters.get(diagnostic_code)?.is_enabled
+    }
+
     /// Get the severity override for a linter based on its diagnostic code
     pub fn get_severity_override(&self, diagnostic_code: &DiagnosticCode) -> Option<Severity> {
         self.linters.get(diagnostic_code)?.severity
@@ -1213,6 +1229,8 @@ pub enum LinterTraitConfig {
 /// Configuration for a specific linter that allows overriding default settings
 #[derive(Deserialize, Serialize, Debug, Clone, Default)]
 pub struct LinterConfig {
+    #[serde(rename = "enabled")]
+    pub is_enabled: Option<bool>,
     pub severity: Option<Severity>,
     pub include_tests: Option<bool>,
     pub include_generated: Option<bool>,
@@ -3486,6 +3504,7 @@ baz(1)->4.
         lint_config.linters.insert(
             DiagnosticCode::NoGarbageCollect,
             LinterConfig {
+                is_enabled: None,
                 severity: Some(Severity::Error),
                 include_tests: None,
                 include_generated: None,
@@ -3527,6 +3546,7 @@ baz(1)->4.
         lint_config.linters.insert(
             DiagnosticCode::NoGarbageCollect,
             LinterConfig {
+                is_enabled: None,
                 severity: None,
                 include_tests: Some(true),
                 include_generated: None,
@@ -3567,6 +3587,7 @@ baz(1)->4.
         lint_config.linters.insert(
             DiagnosticCode::NoGarbageCollect,
             LinterConfig {
+                is_enabled: None,
                 severity: None,
                 include_tests: None,
                 include_generated: Some(true),
@@ -3608,6 +3629,7 @@ baz(1)->4.
         lint_config.linters.insert(
             DiagnosticCode::NoGarbageCollect,
             LinterConfig {
+                is_enabled: None,
                 severity: None,
                 include_tests: None,
                 include_generated: None,
@@ -3644,4 +3666,44 @@ baz(1)->4.
             ),
         );
     }
+
+    #[test]
+    fn test_linter_is_enabled_override() {
+        let mut lint_config = LintConfig::default();
+        lint_config.linters.insert(
+            DiagnosticCode::NoGarbageCollect,
+            LinterConfig {
+                is_enabled: Some(false),
+                severity: None,
+                include_tests: None,
+                include_generated: None,
+                experimental: None,
+                config: None,
+            },
+        );
+
+        let config = DiagnosticsConfig::default()
+            .configure_diagnostics(
+                &lint_config,
+                &Some("no_garbage_collect".to_string()),
+                &None,
+                FallBackToAll::No,
+            )
+            .unwrap();
+        check_diagnostics_with_config(
+            config,
+            r#"
+            //- /src/main.erl
+            -module(main).
+            -export([warning/0]).
+
+            warning() ->
+                erlang:garbage_collect().
+            //- /opt/lib/stdlib-3.17/src/erlang.erl otp_app:/opt/lib/stdlib-3.17
+            -module(erlang).
+            -export([garbage_collect/0]).
+            garbage_collect() -> ok.
+            "#,
+        );
+    }
 }