implement `eval`

3 files changed, 70 insertions, 13 deletions

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 {
diff --git a/src/makefile/input.rs b/src/makefile/input.rs
index 918ce0a..f269fa4 100644
--- a/src/makefile/input.rs
+++ b/src/makefile/input.rs
@@ -2,7 +2,7 @@ use std::cell::Cell;
 use std::collections::HashMap;
 use std::error::Error as StdError;
 use std::fs::File;
-use std::io::{BufRead, BufReader, Error as IoError, Lines};
+use std::io::{BufRead, BufReader, Cursor, Error as IoError, Lines};
 use std::iter::Peekable;
 use std::path::Path;
 
@@ -181,7 +181,10 @@ impl<'a, R: BufRead> MakefileReader<'a, R> {
                 // POSIX says we only have to handle a single filename, but GNU make
                 // handles arbitrarily many filenames, and it's not like that's more work
                 for field in fields {
-                    self.extend(MakefileReader::read_file(self.args, field)?);
+                    self.extend(
+                        MakefileReader::read_file(self.args, field)
+                            .with_context(|| format!("while including {}", field))?,
+                    );
                 }
                 continue;
             }
@@ -202,7 +205,18 @@ impl<'a, R: BufRead> MakefileReader<'a, R> {
 
             // before we actually test it, see if it's only visible after expanding macros
             let (line_tokens, line_type) = if let LineType::Unknown = line_type {
-                let line_tokens = TokenString::text(self.expand_macros(&line_tokens)?);
+                let line_tokens = TokenString::text(self.expand_macros(&line_tokens)?.trim());
+                // and let's eval whatever bullshit needs evaling
+                #[cfg(feature = "full")]
+                {
+                    let eval = self.macros.to_eval.take();
+                    for eval in eval {
+                        self.extend(
+                            MakefileReader::read(self.args, Cursor::new(eval))
+                                .context("while evaling")?,
+                        );
+                    }
+                }
                 let line_type = LineType::of(&line_tokens);
                 (line_tokens, line_type)
             } else {
@@ -499,8 +513,6 @@ impl<'a, R: BufRead> MakefileReader<'a, R> {
 
 #[cfg(test)]
 mod test {
-    use std::io::Cursor;
-
     use super::*;
 
     type R = Result<()>;
@@ -545,7 +557,7 @@ endef
     }
 
     #[test]
-    #[ignore = "I still haven't implemented `eval` or %-based macro substitution."]
+    #[cfg(feature = "full")]
     fn eval() -> R {
         // This, for the record, is a terrible misfeature.
         // If you need this, you probably shouldn't be using Make.
@@ -574,10 +586,10 @@ endef
 $(foreach prog,$(PROGRAMS),$(eval $(call PROGRAM_template,$(prog))))
 
 $(PROGRAMS):
-        $(LINK.o) $^ $(LDLIBS) -o $@
+\t$(LINK.o) $^ $(LDLIBS) -o $@
 
 clean:
-        rm -f $(ALL_OBJS) $(PROGRAMS)
+\trm -f $(ALL_OBJS) $(PROGRAMS)
         ";
 
         let args = Args::empty();
diff --git a/src/makefile/macro.rs b/src/makefile/macro.rs
index 7fbb4a6..a1f2378 100644
--- a/src/makefile/macro.rs
+++ b/src/makefile/macro.rs
@@ -1,6 +1,10 @@
+#[cfg(feature = "full")]
+use std::cell::RefCell;
 use std::collections::HashMap;
 use std::env;
 use std::fmt;
+#[cfg(feature = "full")]
+use std::rc::Rc;
 
 use eyre::{bail, Result, WrapErr};
 use regex::Regex;
@@ -26,6 +30,8 @@ pub struct Set<'parent, 'lookup> {
     parent: Option<&'parent Set<'parent, 'lookup>>,
     data: HashMap<String, (Source, TokenString)>,
     lookup_internal: Option<&'lookup dyn LookupInternal>,
+    #[cfg(feature = "full")]
+    pub to_eval: Rc<RefCell<Vec<String>>>,
 }
 
 impl<'parent, 'lookup> Set<'parent, 'lookup> {
@@ -34,6 +40,8 @@ impl<'parent, 'lookup> Set<'parent, 'lookup> {
             parent: None,
             data: HashMap::new(),
             lookup_internal: None,
+            #[cfg(feature = "full")]
+            to_eval: Rc::new(RefCell::new(Vec::new())),
         }
     }
 
@@ -58,7 +66,10 @@ impl<'parent, 'lookup> Set<'parent, 'lookup> {
         } else if let Some(parent) = self.parent {
             parent.lookup_internal(name)
         } else {
-            bail!("no lookup possible")
+            bail!(
+                "tried to lookup {:?} but no lookup function is available",
+                name
+            )
         }
     }
 
@@ -121,7 +132,12 @@ impl<'parent, 'lookup> Set<'parent, 'lookup> {
                 }
                 #[cfg(feature = "full")]
                 Token::FunctionCall { name, args } => {
-                    result.push_str(&functions::expand_call(name, args, self)?);
+                    result.push_str(&functions::expand_call(
+                        name,
+                        args,
+                        self,
+                        Some(Rc::clone(&self.to_eval)),
+                    )?);
                 }
             }
         }
@@ -146,6 +162,8 @@ impl<'parent, 'lookup> Set<'parent, 'lookup> {
             parent: Some(self),
             data: HashMap::new(),
             lookup_internal: Some(lookup),
+            #[cfg(feature = "full")]
+            to_eval: Default::default(),
         }
     }
 
@@ -155,6 +173,8 @@ impl<'parent, 'lookup> Set<'parent, 'lookup> {
             parent: Some(self),
             data: HashMap::new(),
             lookup_internal: None,
+            #[cfg(feature = "full")]
+            to_eval: Default::default(),
         }
     }
 }