feat: surface stale-CODEOWNERS diff as info output instead of inline error

src/ownership/validator.rs

@@ -208,18 +208,34 @@ impl Error {
 
                 vec![messages.join("\n")]
             }
-            Error::CodeownershipFileIsStale { executable_name: _, diff } => {
-                if diff.is_empty() {
-                    vec![]
-                } else {
-                    vec![format!("The following changes are required (- current, + expected):\n{diff}")]
-                }
-            }
+            // The diff is intentionally *not* rendered as part of the error. It is
+            // surfaced separately as an informational message (see `Errors::info_messages`)
+            // so that a long diff doesn't bury the actionable headline.
+            Error::CodeownershipFileIsStale { .. } => vec![],
             Error::InvalidTeam { name, path } => vec![format!("- {} is referencing an invalid team - '{}'", path.to_string_lossy(), name)],
         }
     }
 }
 
+impl Errors {
+    /// Supplementary detail that explains *what* is wrong without itself being an error.
+    /// The stale-CODEOWNERS diff is surfaced here, as informational output, rather than
+    /// inline with the error so that a long diff doesn't bury the actionable headline in
+    /// CI logs (and so the wrapping `code_ownership` gem raises only the headline rather
+    /// than the entire diff).
+    pub fn info_messages(&self) -> Vec<String> {
+        self.0
+            .iter()
+            .filter_map(|error| match error {
+                Error::CodeownershipFileIsStale { diff, .. } if !diff.is_empty() => {
+                    Some(format!("The following changes are required (- current, + expected):\n{diff}"))
+                }
+                _ => None,
+            })
+            .collect()
+    }
+}
+
 impl Display for Errors {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         let grouped_errors = self.0.iter().into_group_map_by(|error| error.category());

src/runner.rs

@@ -128,6 +128,9 @@ impl Runner {
         match self.ownership.validate() {
             Ok(_) => RunResult::default(),
             Err(err) => RunResult {
+                // The stale-CODEOWNERS diff (if any) rides along as informational output,
+                // printed ahead of the errors, so the actionable headline isn't buried.
+                info_messages: err.info_messages(),
                 validation_errors: vec![format!("{}", err)],
                 ..Default::default()
             },

tests/executable_name_config_test.rs

@@ -41,8 +41,6 @@ fn test_custom_executable_name_full_error_message() -> Result<(), Box<dyn Error>
         false,
         OutputStream::Stdout,
         predicate::eq(indoc! {r#"
-
-    CODEOWNERS out of date. Run `bin/codeownership validate` to update the CODEOWNERS file
     The following changes are required (- current, + expected):
     -# Outdated content to trigger validation error
     -/app/old.rb @FooTeam
@@ -57,6 +55,8 @@ fn test_custom_executable_name_full_error_message() -> Result<(), Box<dyn Error>
     +/config/teams/foo.yml @FooTeam
     +/config/teams/payments.yml @PaymentTeam
 
+    CODEOWNERS out of date. Run `bin/codeownership validate` to update the CODEOWNERS file
+
     "#}),
     )?;
     Ok(())
@@ -71,8 +71,6 @@ fn test_default_executable_name_full_error_message() -> Result<(), Box<dyn Error
         false,
         OutputStream::Stdout,
         predicate::eq(indoc! {r#"
-
-    CODEOWNERS out of date. Run `codeowners generate` to update the CODEOWNERS file
     The following changes are required (- current, + expected):
     -# Outdated content to trigger validation error
     -/app/old.rb @BarTeam
@@ -82,6 +80,8 @@ fn test_default_executable_name_full_error_message() -> Result<(), Box<dyn Error
     +# Team YML ownership
     +/config/teams/bar.yml @BarTeam
 
+    CODEOWNERS out of date. Run `codeowners generate` to update the CODEOWNERS file
+
     "#}),
     )?;
     Ok(())

tests/invalid_project_test.rs

@@ -14,8 +14,6 @@ fn test_validate() -> Result<(), Box<dyn Error>> {
         false,
         OutputStream::Stdout,
         predicate::eq(indoc! {"
-
-    CODEOWNERS out of date. Run `codeowners generate` to update the CODEOWNERS file
     The following changes are required (- current, + expected):
     +# STOP! - DO NOT EDIT THIS FILE MANUALLY
     +# This file was automatically generated by \"bin/codeownership validate\".
@@ -47,6 +45,8 @@ fn test_validate() -> Result<(), Box<dyn Error>> {
     +# Team owned gems
     +/gems/payroll_calculator/**/** @PayrollTeam
 
+    CODEOWNERS out of date. Run `codeowners generate` to update the CODEOWNERS file
+
     Code ownership should only be defined for each file in one way. The following files have declared ownership in multiple ways
 
     gems/payroll_calculator/calculator.rb