feat(cli): add --check-plurals to view and CLI tests

- Validate plural completeness per locale with exit status
- Add tests for missing and complete English plural forms

- Validate plural completeness per locale with exit status
- Add tests for missing and complete English plural forms

- Replace match-based rules with lazy_static BTreeMap keyed by base language
- Remove region/script variants unreachable with base-language selection
- Keep conservative default to {Other}

- Add PluralValidationReport with missing/have sets
- Add collect_resource_plural_issues and Codec::collect_plural_issues
- Refactor validate_plurals to fold reports into an Error

Author: WendellXY

langcodec-cli/src/main.rs

@@ -74,6 +74,10 @@ enum Commands {
         /// Display full value without truncation (even in terminal)
         #[arg(long)]
         full: bool,
+
+        /// Validate plural completeness against CLDR category sets
+        #[arg(long, default_value_t = false)]
+        check_plurals: bool,
     },
 
     /// Merge multiple localization files into one output file with automatic format detection and conversion.
@@ -187,7 +191,7 @@ fn main() {
                 },
             );
         }
-        Commands::View { input, lang, full } => {
+        Commands::View { input, lang, full, check_plurals } => {
             // Create validation context
             let mut context = ValidationContext::new().with_input_file(input.clone());
 
@@ -223,6 +227,16 @@ fn main() {
             }
 
             print_view(&codec, &lang, full);
+
+            if check_plurals {
+                match codec.validate_plurals() {
+                    Ok(()) => println!("\n✅ Plural validation passed"),
+                    Err(e) => {
+                        eprintln!("\n❌ Plural validation failed: {}", e);
+                        std::process::exit(2);
+                    }
+                }
+            }
         }
         Commands::Merge {
             inputs,

langcodec-cli/tests/plural_validation_cli_tests.rs

@@ -0,0 +1,82 @@
+use std::fs;
+use std::process::Command;
+use tempfile::TempDir;
+
+#[test]
+fn test_cli_view_check_plurals_fails_on_missing() {
+    let temp_dir = TempDir::new().unwrap();
+    let input_file = temp_dir.path().join("strings.xml");
+
+    // English requires 'one' and 'other'; provide only 'other'
+    let xml = r#"
+        <resources>
+            <plurals name="apples" translatable="true">
+                <item quantity="other">%d apples</item>
+            </plurals>
+        </resources>
+    "#;
+    fs::write(&input_file, xml).unwrap();
+
+    let output = Command::new("cargo")
+        .args([
+            "run",
+            "--quiet",
+            "--",
+            "view",
+            "-i",
+            input_file.to_str().unwrap(),
+            "--lang",
+            "en",
+            "--check-plurals",
+        ])
+        .output()
+        .unwrap();
+
+    assert!(
+        !output.status.success(),
+        "CLI unexpectedly succeeded: {}",
+        String::from_utf8_lossy(&output.stdout)
+    );
+    let stderr = String::from_utf8_lossy(&output.stderr);
+    assert!(stderr.contains("Plural validation failed"), "stderr: {}", stderr);
+}
+
+#[test]
+fn test_cli_view_check_plurals_passes_when_complete() {
+    let temp_dir = TempDir::new().unwrap();
+    let input_file = temp_dir.path().join("strings.xml");
+
+    // English: provide 'one' and 'other'
+    let xml = r#"
+        <resources>
+            <plurals name="apples" translatable="true">
+                <item quantity="one">One apple</item>
+                <item quantity="other">%d apples</item>
+            </plurals>
+        </resources>
+    "#;
+    fs::write(&input_file, xml).unwrap();
+
+    let output = Command::new("cargo")
+        .args([
+            "run",
+            "--quiet",
+            "--",
+            "view",
+            "-i",
+            input_file.to_str().unwrap(),
+            "--lang",
+            "en",
+            "--check-plurals",
+        ])
+        .output()
+        .unwrap();
+
+    assert!(
+        output.status.success(),
+        "CLI failed: {}",
+        String::from_utf8_lossy(&output.stderr)
+    );
+    let stdout = String::from_utf8_lossy(&output.stdout);
+    assert!(stdout.contains("✅ Plural validation passed"));
+}