feat(dev): Example macro out of order with tests

COVERAGE.md

@@ -0,0 +1,35 @@
+# Code Coverage
+
+## Quick Start
+
+```bash
+# Install cargo-llvm-cov (first time only)
+cargo install cargo-llvm-cov
+
+# Run coverage and open HTML report
+cargo llvm-cov --html --open
+
+# Run coverage for specific tests
+cargo llvm-cov --html --open -- test_name
+```
+
+## Reports
+
+HTML report location: `target/llvm-cov/html/index.html`
+
+## Coverage Summary
+
+View text summary:
+```bash
+cargo llvm-cov report --summary-only
+```
+
+## Notes
+
+- Trybuild compile-time tests do not appear in coverage reports (they verify compile errors, not runtime behavior)
+- Coverage measures runtime test execution only
+- Current project coverage: ~74% lines, ~68% functions
+
+## Reference
+
+- [cargo-llvm-cov documentation](https://github.com/taiki-e/cargo-llvm-cov)

Cargo.toml

@@ -263,6 +263,7 @@ regex = { version = "1", default-features = false, features = ["std", "perf", "u
 paste = { version = "1", default-features = false }
 proptest = { version = "1" }
 proptest-derive = { version = "0.6" }
+trybuild = "1.0.114"
 
 [build-dependencies]
 lalrpop = { version = "0.22", default-features = false }

scripts/check_deny.sh

@@ -1,8 +1,8 @@
 #!/bin/bash
 
-if ! cargo install --list | grep -q "cargo-deny v0.18.3"; then
+if ! cargo install --list | grep -q "cargo-deny v0.19.0"; then
     echo "Install cargo-deny"
-    cargo install cargo-deny --version 0.18.3 --force --locked
+    cargo install cargo-deny --version 0.19.0 --force --locked
 fi
 
 echo "Check deny"

src/compiler/function.rs

@@ -87,7 +87,55 @@ pub struct Example {
 /// Macro to create an `Example` with automatic source location tracking
 /// Accepts fields in any order: title, source, result
 /// Optional fields added to `Example` shouldn't be required to be added for the macro to work,
-/// mainting backwards compatibility
+/// maintaining backwards compatibility
+///
+/// # Examples
+///
+/// Valid usage:
+/// ```
+/// use vrl::example;
+///
+/// let ex = example! {
+///     title: "test",
+///     source: "code",
+///     result: Ok("output"),
+/// };
+/// ```
+///
+/// Missing required field should fail:
+/// ```compile_fail
+/// use vrl::example;
+///
+/// let ex = example! {
+///     title: "test",
+///     source: "code",
+///     // missing result field
+/// };
+/// ```
+///
+/// Duplicate field should fail:
+/// ```compile_fail
+/// use vrl::example;
+///
+/// let ex = example! {
+///     title: "test",
+///     source: "code",
+///     result: Ok("output"),
+///     title: "duplicate",
+/// };
+/// ```
+///
+/// Unknown field should fail:
+/// ```compile_fail
+/// use vrl::example;
+///
+/// let ex = example! {
+///     title: "test",
+///     source: "code",
+///     result: Ok("output"),
+///     unknown_field: "value",
+/// };
+/// ```
 #[macro_export]
 macro_rules! example {
     // Entry point - delegate to internal parser with empty state
@@ -97,6 +145,21 @@ macro_rules! example {
         $crate::example!(@internal [] [] [] [$($field: $value,)*])
     };
 
+    // Error: duplicate title field
+    (@internal [$title:expr] [$($source:tt)*] [$($result:tt)*] [title: $t:expr, $($rest:tt)*]) => {
+        compile_error!("duplicate 'title' field in example! macro")
+    };
+
+    // Error: duplicate source field
+    (@internal [$($title:tt)*] [$source:expr] [$($result:tt)*] [source: $s:expr, $($rest:tt)*]) => {
+        compile_error!("duplicate 'source' field in example! macro")
+    };
+
+    // Error: duplicate result field
+    (@internal [$($title:tt)*] [$($source:tt)*] [$result:expr] [result: $r:expr, $($rest:tt)*]) => {
+        compile_error!("duplicate 'result' field in example! macro")
+    };
+
     // Parse title field
     (@internal [$($title:tt)*] [$($source:tt)*] [$($result:tt)*] [title: $t:expr, $($rest:tt)*]) => {
         $crate::example!(@internal [$t] [$($source)*] [$($result)*] [$($rest)*])
@@ -714,4 +777,27 @@ mod tests {
         assert_eq!(ex3.source, "code3");
         assert_eq!(ex3.result, Err("error3"));
     }
+
+    #[test]
+    fn test_example_macro_trailing_commas() {
+        // Test with trailing comma
+        let ex_with_comma = example! {
+            title: "test",
+            source: "code",
+            result: Ok("ok"),
+        };
+        assert_eq!(ex_with_comma.title, "test");
+        assert_eq!(ex_with_comma.source, "code");
+        assert_eq!(ex_with_comma.result, Ok("ok"));
+
+        // Test without trailing comma
+        let ex_no_comma = example! {
+            title: "test",
+            source: "code",
+            result: Ok("ok")
+        };
+        assert_eq!(ex_no_comma.title, "test");
+        assert_eq!(ex_no_comma.source, "code");
+        assert_eq!(ex_no_comma.result, Ok("ok"));
+    }
 }

src/stdlib/parse_klog.rs

@@ -89,7 +89,7 @@ impl Function for ParseKlog {
                     "level": "info",
                     "line": 70,
                     "message": "hello from klog",
-                    "timestamp": "2025-05-05T17:59:40.692994Z"
+                    "timestamp": "{CURRENT_YEAR}-05-05T17:59:40.692994Z"
                 }"#}),
         }]
     }

src/stdlib/parse_linux_authorization.rs

@@ -27,7 +27,7 @@ impl Function for ParseLinuxAuthorization {
                 "hostname": "localhost",
                 "message": "Accepted publickey for eng from 10.1.1.1 port 8888 ssh2: RSA SHA256:foobar",
                 "procid": 1111,
-                "timestamp": "2025-03-23T01:49:58Z"
+                "timestamp": "{CURRENT_YEAR}-03-23T01:49:58Z"
             }"#}),
         }]
     }

src/test/mod.rs

@@ -208,7 +208,7 @@ fn process_result(
             let got_value = vrl_value_to_json_value(got);
             let mut failed = false;
 
-            let want = test.result.clone();
+            let want = replace_current_year_placeholder(test.result.clone());
             let want_value = if want.starts_with("r'") && want.ends_with('\'') {
                 match regex::Regex::new(&want[2..want.len() - 1].replace("\\'", "'")) {
                     Ok(regex) => regex.to_string().into(),
@@ -257,7 +257,7 @@ fn process_result(
         Err(err) => {
             let mut failed = false;
             let got = err.to_string().trim().to_owned();
-            let want = test.result.clone().trim().to_owned();
+            let want = replace_current_year_placeholder(test.result.clone().trim().to_owned());
 
             if (test.result_approx && compare_partial_diagnostic(&got, &want)) || got == want {
                 println!("{}{}", Colour::Green.bold().paint("OK"), timings);
@@ -319,7 +319,7 @@ fn process_compilation_diagnostics(
     let got = formatter.to_string();
     let got = got.trim();
 
-    let want = test.result.clone();
+    let want = replace_current_year_placeholder(test.result.clone());
     let want = want.trim();
 
     if (test.result_approx && compare_partial_diagnostic(got, want)) || got == want {
@@ -404,6 +404,11 @@ fn print_result(
     std::process::exit(code)
 }
 
+fn replace_current_year_placeholder(input: String) -> String {
+    let current_year = Utc::now().format("%Y").to_string();
+    input.replace("{CURRENT_YEAR}", &current_year)
+}
+
 fn compare_partial_diagnostic(got: &str, want: &str) -> bool {
     got.lines()
         .filter(|line| line.trim().starts_with("error[E"))