Merge nucleic/sleek-thistle-egret-fyej into dev

brush-builtins/src/let_.rs

@@ -0,0 +1,41 @@
+use clap::Parser;
+use std::io::Write;
+
+use brush_core::{ExecutionExitCode, ExecutionResult, arithmetic::Evaluatable, builtins};
+
+/// Evaluate arithmetic expressions.
+#[derive(Parser)]
+pub(crate) struct LetCommand {
+    /// Arithmetic expressions to evaluate.
+    #[arg(trailing_var_arg = true, allow_hyphen_values = true)]
+    exprs: Vec<String>,
+}
+
+impl builtins::Command for LetCommand {
+    type Error = brush_core::Error;
+
+    async fn execute<SE: brush_core::ShellExtensions>(
+        &self,
+        context: brush_core::ExecutionContext<'_, SE>,
+    ) -> Result<brush_core::ExecutionResult, Self::Error> {
+        let mut result = ExecutionExitCode::InvalidUsage.into();
+
+        if self.exprs.is_empty() {
+            writeln!(context.stderr(), "missing expression")?;
+            return Ok(result);
+        }
+
+        for expr in &self.exprs {
+            let parsed = brush_parser::arithmetic::parse(expr.as_str())?;
+            let evaluated = parsed.eval(context.shell)?;
+
+            if evaluated == 0 {
+                result = ExecutionResult::general_error();
+            } else {
+                result = ExecutionResult::success();
+            }
+        }
+
+        Ok(result)
+    }
+}