Add support for ascii formatting of f-strings.

tests/snippets/fstrings.py

@@ -39,9 +39,17 @@ v = Value()
 assert f'{v}' == 'foo'
 assert f'{v!r}' == 'bar'
 assert f'{v!s}' == 'baz'
+assert f'{v!a}' == 'bar'
 
 # advanced expressions:
 
 assert f'{True or True}' == 'True'
 assert f'{1 == 1}' == 'True'
 assert f'{"0" if True else "1"}' == '0'
+
+# Test ascii representation of unicodes:
+v = "\u262e"
+assert f'>{v}' == '>\u262e'
+assert f'>{v!r}' == ">'\u262e'"
+assert f'>{v!s}' == '>\u262e'
+assert f'>{v!a}' == r">'\u262e'"

vm/src/builtins.rs

@@ -60,8 +60,15 @@ fn builtin_any(iterable: PyIterable<bool>, vm: &VirtualMachine) -> PyResult<bool
 
 fn builtin_ascii(obj: PyObjectRef, vm: &VirtualMachine) -> PyResult<String> {
     let repr = vm.to_repr(&obj)?;
+    let ascii = to_ascii(&repr.value);
+    Ok(ascii)
+}
+
+/// Convert a string to ascii compatible, escaping unicodes into escape
+/// sequences.
+pub fn to_ascii(value: &str) -> String {
     let mut ascii = String::new();
-    for c in repr.value.chars() {
+    for c in value.chars() {
         if c.is_ascii() {
             ascii.push(c)
         } else {
@@ -74,7 +81,7 @@ fn builtin_ascii(obj: PyObjectRef, vm: &VirtualMachine) -> PyResult<String> {
             ascii.push_str(&hex)
         }
     }
-    Ok(ascii)
+    ascii
 }
 
 fn builtin_bin(x: PyIntRef, _vm: &VirtualMachine) -> String {

vm/src/eval.rs

@@ -17,17 +17,14 @@ pub fn eval(vm: &VirtualMachine, source: &str, scope: Scope, source_path: &str)
 mod tests {
     use super::eval;
     use super::VirtualMachine;
+    use crate::pyobject::IdProtocol;
 
     #[test]
     fn test_print_42() {
         let source = String::from("print('Hello world')");
-        let vm: VirtualMachine = Default::default();
+        let vm = VirtualMachine::default();
         let vars = vm.new_scope_with_builtins();
-        let _result = eval(&vm, &source, vars, "<unittest>");
-
-        // TODO: check result?
-        //assert_eq!(
-        //    parse_ast,
-        // );
+        let result = eval(&vm, &source, vars, "<unittest>").expect("this should pass");
+        assert!(result.is(&vm.ctx.none()));
     }
 }

vm/src/frame.rs

@@ -666,7 +666,7 @@ impl Frame {
                 let value = match conversion {
                     Some(Str) => vm.to_str(&self.pop_value())?.into_object(),
                     Some(Repr) => vm.to_repr(&self.pop_value())?.into_object(),
-                    Some(Ascii) => self.pop_value(), // TODO
+                    Some(Ascii) => vm.to_ascii(&self.pop_value())?,
                     None => self.pop_value(),
                 };
 

vm/src/vm.rs

@@ -11,7 +11,7 @@ use std::fmt;
 use std::rc::Rc;
 use std::sync::{Mutex, MutexGuard};
 
-use crate::builtins;
+use crate::builtins::{self, to_ascii};
 use crate::bytecode;
 use crate::frame::{ExecutionResult, Frame, FrameRef};
 use crate::frozen;
@@ -445,6 +445,13 @@ impl VirtualMachine {
         TryFromObject::try_from_object(self, repr)
     }
 
+    pub fn to_ascii(&self, obj: &PyObjectRef) -> PyResult {
+        let repr = self.call_method(obj, "__repr__", vec![])?;
+        let repr: PyStringRef = TryFromObject::try_from_object(self, repr)?;
+        let ascii = to_ascii(&repr.value);
+        Ok(self.new_str(ascii))
+    }
+
     pub fn import(&self, module: &str, from_list: &PyObjectRef, level: usize) -> PyResult {
         // if the import inputs seem weird, e.g a package import or something, rather than just
         // a straight `import ident`