Add append() function (casey#2046)

README.md

@@ -1397,7 +1397,8 @@ The process ID is: 420
 
 
 #### String Manipulation
-
+- `append(suffix, s)`<sup>master</sup> Append `suffix` to whitespace-separated
+  strings in `s`.
 - `quote(s)` - Replace all single quotes with `'\''` and prepend and append
   single quotes to `s`. This is sufficient to escape special characters for
   many shells, including most Bourne shell descendants.

src/function.rs

@@ -20,6 +20,7 @@ pub(crate) enum Function {
 pub(crate) fn get(name: &str) -> Option<Function> {
   let function = match name {
     "absolute_path" => Unary(absolute_path),
+    "append" => Binary(append),
     "arch" => Nullary(arch),
     "blake3" => Unary(blake3),
     "blake3_file" => Unary(blake3_file),
@@ -105,6 +106,15 @@ fn absolute_path(context: &FunctionContext, path: &str) -> Result<String, String
   }
 }
 
+fn append(_context: &FunctionContext, suffix: &str, s: &str) -> Result<String, String> {
+  Ok(
+    s.split_whitespace()
+      .map(|s| format!("{s}{suffix}"))
+      .collect::<Vec<String>>()
+      .join(" "),
+  )
+}
+
 fn arch(_context: &FunctionContext) -> Result<String, String> {
   Ok(target::arch().to_owned())
 }

tests/functions.rs

@@ -481,6 +481,26 @@ fn trim_end() {
   assert_eval_eq("trim_end('  f  ')", "  f");
 }
 
+#[test]
+fn append() {
+  assert_eval_eq("append('8', 'r s t')", "r8 s8 t8");
+  assert_eval_eq("append('.c', 'main sar x11')", "main.c sar.c x11.c");
+  assert_eval_eq("append('-', 'c v h y')", "c- v- h- y-");
+  assert_eval_eq(
+    "append('0000', '11 10 01 00')",
+    "110000 100000 010000 000000",
+  );
+  assert_eval_eq(
+    "append('tion', '
+    Determina
+    Acquisi
+    Motiva
+    Conjuc
+    ')",
+    "Determination Acquisition Motivation Conjuction",
+  );
+}
+
 #[test]
 #[cfg(not(windows))]
 fn join() {