fix(linter): add summary output to GitHub formatter

apps/oxlint/src/output_formatter/default.rs

@@ -87,7 +87,7 @@ impl DiagnosticReporter for GraphicalReporter {
     }
 }
 
-fn get_diagnostic_result_output(result: &DiagnosticResult) -> String {
+pub(super) fn get_diagnostic_result_output(result: &DiagnosticResult) -> String {
     let mut output = String::new();
 
     if result.warnings_count() + result.errors_count() > 0 {

apps/oxlint/src/output_formatter/github.rs

@@ -5,6 +5,7 @@ use oxc_diagnostics::{
     reporter::{DiagnosticReporter, DiagnosticResult, Info},
 };
 
+use super::default::get_diagnostic_result_output;
 use crate::output_formatter::InternalFormatter;
 
 #[derive(Debug)]
@@ -21,8 +22,8 @@ impl InternalFormatter for GithubOutputFormatter {
 struct GithubReporter;
 
 impl DiagnosticReporter for GithubReporter {
-    fn finish(&mut self, _: &DiagnosticResult) -> Option<String> {
-        None
+    fn finish(&mut self, result: &DiagnosticResult) -> Option<String> {
+        Some(get_diagnostic_result_output(result))
     }
 
     fn render_error(&mut self, error: Error) -> Option<String> {
@@ -95,7 +96,16 @@ mod test {
 
         let result = reporter.finish(&DiagnosticResult::default());
 
-        assert!(result.is_none());
+        assert_eq!(result.unwrap(), "Found 0 warnings and 0 errors.\n");
+    }
+
+    #[test]
+    fn reporter_finish_with_errors() {
+        let mut reporter = GithubReporter;
+
+        let result = reporter.finish(&DiagnosticResult::new(2, 1, false));
+
+        assert_eq!(result.unwrap(), "\nFound 2 warnings and 1 error.\n");
     }
 
     #[test]

apps/oxlint/src/snapshots/fixtures__cli__output_formatter_diagnostic_--format=github --report-unused-disable-directives disable-directive.js@oxlint.snap

@@ -8,6 +8,8 @@ working directory: fixtures/cli/output_formatter_diagnostic
 ::warning file=disable-directive.js,line=9,endLine=9,col=3,endColumn=40,title=oxlint::Unused eslint-disable directive (no problems were reported).
 ::warning file=disable-directive.js,line=12,endLine=12,col=3,endColumn=40,title=oxlint::Unused eslint-disable directive (no problems were reported).
 ::warning file=disable-directive.js,line=15,endLine=15,col=3,endColumn=47,title=oxlint::Unused eslint-disable directive (no problems were reported).
+
+Found 3 warnings and 0 errors.
 ----------
 CLI result: LintSucceeded
 ----------

apps/oxlint/src/snapshots/fixtures__cli__output_formatter_diagnostic_--format=github ok.js@oxlint.snap

@@ -5,6 +5,7 @@ source: apps/oxlint/src/tester.rs
 arguments: --format=github ok.js
 working directory: fixtures/cli/output_formatter_diagnostic
 ----------
+Found 0 warnings and 0 errors.
 ----------
 CLI result: LintSucceeded
 ----------

apps/oxlint/src/snapshots/fixtures__cli__output_formatter_diagnostic_--format=github parser-error.js@oxlint.snap

@@ -6,6 +6,8 @@ arguments: --format=github parser-error.js
 working directory: fixtures/cli/output_formatter_diagnostic
 ----------
 ::error file=parser-error.js,line=3,endLine=3,col=9,endColumn=10,title=oxlint::Expected `;` but found `:`
+
+Found 0 warnings and 1 error.
 ----------
 CLI result: LintFoundErrors
 ----------

apps/oxlint/src/snapshots/fixtures__cli__output_formatter_diagnostic_--format=github test.js@oxlint.snap

@@ -8,6 +8,8 @@ working directory: fixtures/cli/output_formatter_diagnostic
 ::error file=test.js,line=5,endLine=5,col=1,endColumn=10,title=eslint(no-debugger)::`debugger` statement is not allowed
 ::warning file=test.js,line=1,endLine=1,col=10,endColumn=13,title=eslint(no-unused-vars)::Function 'foo' is declared but never used.
 ::warning file=test.js,line=1,endLine=1,col=17,endColumn=18,title=eslint(no-unused-vars)::Parameter 'b' is declared but never used. Unused parameters should start with a '_'.
+
+Found 2 warnings and 1 error.
 ----------
 CLI result: LintFoundErrors
 ----------