From 89a87698ed39188fee792cc3488bffed2ff525cf Mon Sep 17 00:00:00 2001
From: Melody Horn <melody@boringcactus.com>
Date: Sat, 3 Apr 2021 12:26:33 -0600
Subject: implement `eval`

---
 src/makefile/functions.rs | 31 ++++++++++++++++++++++++++++---
 1 file changed, 28 insertions(+), 3 deletions(-)

(limited to 'src/makefile/functions.rs')

diff --git a/src/makefile/functions.rs b/src/makefile/functions.rs
index 43ed44b..a22ec3b 100644
--- a/src/makefile/functions.rs
+++ b/src/makefile/functions.rs
@@ -1,10 +1,18 @@
+use std::cell::RefCell;
+use std::rc::Rc;
+
 use eyre::{bail, Result};
 
 use super::pattern::r#match;
 use super::r#macro::{Set as MacroSet, Source as MacroSource};
 use super::token::TokenString;
 
-pub fn expand_call(name: &str, args: &[TokenString], macros: &MacroSet) -> Result<String> {
+pub fn expand_call(
+    name: &str,
+    args: &[TokenString],
+    macros: &MacroSet,
+    to_eval: Option<Rc<RefCell<Vec<String>>>>,
+) -> Result<String> {
     match name {
         "filter" => {
             assert_eq!(args.len(), 2);
@@ -54,7 +62,16 @@ pub fn expand_call(name: &str, args: &[TokenString], macros: &MacroSet) -> Resul
         }
 
         // eval
-        "eval" => todo!(),
+        "eval" => {
+            assert_eq!(args.len(), 1);
+            let should_eval = eval::eval(macros, &args[0])?;
+            if let Some(to_eval) = to_eval {
+                to_eval.borrow_mut().push(should_eval);
+            } else {
+                bail!("tried to eval something but no eval back-channel was available");
+            }
+            return Ok(String::new());
+        }
 
         "origin" => {
             assert_eq!(args.len(), 1);
@@ -268,6 +285,14 @@ mod call {
     }
 }
 
+mod eval {
+    use super::*;
+
+    pub fn eval(macros: &MacroSet, arg: &TokenString) -> Result<String> {
+        macros.expand(arg)
+    }
+}
+
 mod origin {
     use super::*;
 
@@ -317,7 +342,7 @@ mod test {
     type R = Result<()>;
 
     fn call(name: &str, args: &[TokenString], macros: &MacroSet) -> Result<String> {
-        super::expand_call(name, args, macros)
+        super::expand_call(name, args, macros, None)
     }
 
     macro_rules! call {
-- 
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