expand ~ on windows

src/builtin/ls.rs

@@ -7,7 +7,7 @@ use std::{env, fs, io::Write};
 pub struct Ls;
 
 impl Call for Ls {
-    fn call(&self, ctx: &mut Context, args: &[Value]) -> Result<Value, ExecError> {
+    fn call(&self, ctx: &mut Context, _args: &[Value]) -> Result<Value, ExecError> {
         let cwd = env::current_dir()?;
         let dir = fs::read_dir(&cwd)?;
         for child in dir {

src/error.rs

@@ -1,5 +1,6 @@
 use crate::{
     lex::Token,
+    syntax::ExpandError,
     topo::{Glyph, Position},
 };
 use std::io;
@@ -91,6 +92,9 @@ pub enum ParseError {
     #[error("dangling")]
     DanglingElements,
 
+    #[error("shell expansion error")]
+    ExpansionError(#[from] ExpandError),
+
     #[error("you wouldn't parse a semicolon")]
     WhyParseSemicolon,
 }

src/syntax.rs

@@ -5,7 +5,7 @@ use crate::{
     parse,
     run::{Call, Context, Eval, Value},
 };
-use std::{collections::HashSet, process};
+use std::{collections::HashSet, env, ffi::OsString, process};
 
 /// The differnt types of nodes that may appear in our AST
 #[derive(Debug)]
@@ -170,7 +170,9 @@ impl TreeBuilder {
                 Element::Command(cmd)
             }
             parse::Value::Terminal(Token::Word(word)) => {
-                Element::Literal(Value::Text(word.to_string()))
+                let text = word.to_string();
+                let text = expand(&text)?;
+                Element::Literal(Value::Text(text))
             }
             parse::Value::Terminal(Token::Glob(_)) => {
                 todo!()
@@ -192,7 +194,49 @@ pub fn parse(source: &str) -> Result<Element, ParseError> {
     let parser = parse::Parser::new(tokens);
     let mut parse_tree = parser.parse()?;
     let mut builder = TreeBuilder::new();
-    builder.parse(&mut parse_tree)
+    let root = builder.parse(&mut parse_tree)?;
+    Ok(root)
+}
+
+#[cfg(target_os = "windows")]
+fn home_dir() -> Result<OsString, ExpandError> {
+    env::var_os("HOMEPATH").ok_or(ExpandError::EmptyEnvironmentVar(String::from("HOMEPATH")))
+}
+
+#[derive(thiserror::Error, Debug)]
+pub enum ExpandError {
+    #[error("environment var is not set: {0}")]
+    EmptyEnvironmentVar(String),
+
+    #[error("home dir is not utf-8")]
+    NotUnicode,
+}
+
+fn expand(text: &str) -> Result<String, ExpandError> {
+    let chars = text.chars();
+    let mut escape = false;
+    let mut s = String::new();
+    for c in chars {
+        if !escape && c == '\\' {
+            escape = true;
+            continue;
+        }
+
+        if escape {
+            s.push(c);
+            escape = false;
+            continue;
+        }
+
+        if c == '~' {
+            let p = home_dir()?;
+            s.push_str(p.to_str().ok_or(ExpandError::NotUnicode)?);
+            continue;
+        }
+
+        s.push(c);
+    }
+    Ok(s)
 }
 
 #[cfg(test)]