error printing is less bad

Cargo.toml

@@ -10,7 +10,7 @@ thiserror = "1.0"
 macros = { path = "macros" }
 dirs = "4"
 
-log = { version = "0.4", features = [ "max_level_off", "release_max_level_off" ] }
+log = { version = "0.4", features = [ "max_level_debug", "release_max_level_off" ] }
 
 [dependencies.windows]
 version = "0.44.0"

src/error.rs

@@ -65,11 +65,20 @@ pub enum ParseError {
 
 #[derive(Debug, Error)]
 pub enum ExecError {
-    #[error("failed waiting on child process")]
+    #[error("failed waiting on child process '{name}' ({pid})")]
-    ProcessWaitError(#[source] io::Error),
+    ProcessWaitError {
-
+        name: String,
-    #[error("failed to spawn child process")]
+        pid: u32,
-    ProcessSpawnError(#[source] io::Error),
+        #[source]
+        source: io::Error,
+    },
+
+    #[error("failed to spawn '{name}' as a child process")]
+    ProcessSpawnError {
+        name: String,
+        #[source]
+        source: io::Error,
+    },
 
     #[error("value type error: {0}")]
     ValueTypeError(String),

src/lex.rs

@@ -9,15 +9,16 @@ pub fn lex(source: &str) -> Result<Vec<Token>, LexError> {
     Lexer::new(source).collect()
 }
 
-/// A Lexeme is the text of a given Token, without respect to that Token's type, but with respect
+/// A Lexeme is the text of a given [Token]. The lexeme contains no information about the Token's
-/// to where the text appears relative to some source code. This is, simply, a string that contains
+/// meaning or type; it is just a fancy string with position information.
-/// the addresses of each of its characters with respect to some source text.
 #[derive(PartialEq, Clone)]
 pub struct Lexeme {
     elems: Vec<Glyph>,
 }
 
 impl Lexeme {
+    /// The area of the input text covered by this lexeme. This might return none of the Lexeme is
+    /// an empty string.
     fn span(&self) -> Option<Range<Position>> {
         if self.elems.is_empty() {
             return None;
@@ -75,6 +76,10 @@ pub enum Token {
 }
 
 impl Token {
+    /// Checks whether or not another token has the same contents as this Token. The eq
+    /// implementation will also consider positional information, whereas the `same` function does
+    /// not.
+    #[allow(unused)]
     fn same(&self, other: &Self) -> bool {
         use Token::*;
 
@@ -86,17 +91,20 @@ impl Token {
     }
 }
 
+/// Tokenizer splits some input [Glyphs] into [Token] values
 pub struct Tokenizer<'text> {
     source: Glyphs<'text>,
 }
 
 impl<'text> Tokenizer<'text> {
+    /// creates a new tokenizer for some given input source text
     pub fn new(text: &'text str) -> Self {
         Self {
             source: Glyphs::new(text),
         }
     }
 
+    /// produces the next token in our input source text. If we've hit EOF, this will return None.
     fn next_token(&mut self) -> Option<Result<Token, LexError>> {
         self.source.yeet_whitespace();
         let next = self.source.next()?;
@@ -235,7 +243,7 @@ mod tests {
             .chars()
             .map(|c| Glyph {
                 glyph: c,
-                position: Position::start(),
+                position: Position::origin(),
                 bytes: 0..0,
             })
             .collect();

src/main.rs

@@ -1,16 +1,38 @@
+/// hi
+
+/// builtin functions
 mod builtins;
+
+/// all of the errors for the clyde project live in this module
 mod error;
+
 mod ext;
+
+/// handles input from terminals
 mod input;
+
+/// key presses, independent from input sources
 mod key;
+
+/// lexical analysis
 mod lex;
+
+/// a real primitive line editor
 mod line;
+
 mod log;
 mod output;
+
+/// turns our tokens into parse trees
 mod parse;
+
 mod prompt;
 mod shell;
+
+/// syntax and semantic analysis
 mod syntax;
+
+/// topoglyph is a real word, i promise
 mod topo;
 
 use crate::log::*;
@@ -68,12 +90,12 @@ fn main() -> Result<()> {
                             let mut state = syntax::State::new();
                             if let Err(e) = tree.eval(&mut state) {
                                 error!("{e:?}");
-                                println!("Error: {e:?}");
+                                shell.render_error(e);
                             }
                         }
                         Err(e) => {
                             error!("{e:?}");
-                            println!("Error: {e:?}");
+                            shell.render_error(e);
                         }
                     }
                     // shell.exec(tree.into())?;
@@ -202,7 +224,3 @@ fn main() -> Result<()> {
         }
     }
 }
-
-/*
-
-*/

src/output.rs

@@ -103,7 +103,7 @@ impl Writer {
         unsafe {
             let handle = Console::GetStdHandle(Console::STD_OUTPUT_HANDLE)
                 .context("unable to get stdout handle")?;
-            let mut stdout = Self{output: handle};
+            let mut stdout = Self { output: handle };
             stdout.reset()?;
             Ok(stdout)
         }
@@ -146,11 +146,6 @@ impl Writer {
         self.write(b"\x1b[2J\x1b[0;0H")?;
         Ok(())
     }
-
-    // pub fn hide_cursor(&mut self) -> Result<()> {
-    //     self.write(b"\x1b[?25l")?;
-    //     Ok(())
-    // }
 }
 
 impl Write for Writer {

src/shell.rs

@@ -6,7 +6,12 @@ use crate::{
     output, syntax,
 };
 
-use std::path::{Path, PathBuf};
+use std::{
+    error::Error,
+    fmt,
+    io::{self, Write},
+    path::{Path, PathBuf},
+};
 
 use anyhow::Result;
 use dirs;
@@ -153,4 +158,21 @@ impl Shell {
             }
         }
     }
+
+    pub fn render_error<E: Error>(&mut self, e: E) -> io::Result<()> {
+        self.render_error_helper(e, 0)?;
+        Ok(())
+    }
+
+    fn render_error_helper<E: Error>(&mut self, e: E, depth: u8) -> io::Result<()> {
+        if depth > 0 {
+            println!("  {e}");
+        } else {
+            println!("{e}:");
+        }
+        if let Some(cause) = e.source() {
+            self.render_error_helper(cause, depth + 1)?;
+        }
+        Ok(())
+    }
 }

src/syntax.rs

@@ -103,7 +103,7 @@ pub struct Command {
 impl Eval for Command {
     fn eval(&self, ctx: &mut State) -> Result<Value, ExecError> {
         let name = self.name.eval(ctx)?.try_to_string()?;
-        let mut proc = process::Command::new(name);
+        let mut proc = process::Command::new(&name);
 
         if self.args.len() > 0 {
             let args = self
@@ -113,8 +113,16 @@ impl Eval for Command {
                 .collect::<Result<Vec<String>, ExecError>>()?;
             proc.args(args);
         }
-        let mut child = proc.spawn().map_err(|e| ExecError::ProcessSpawnError(e))?;
+        let mut child = proc.spawn().map_err(|e| ExecError::ProcessSpawnError {
-        let status = child.wait().map_err(|e| ExecError::ProcessWaitError(e))?;
+            name: name.clone(),
+            source: e,
+        })?;
+        let pid = child.id();
+        let status = child.wait().map_err(|e| ExecError::ProcessWaitError {
+            name,
+            pid,
+            source: e,
+        })?;
         return Ok(Value::ExitStatus(status));
     }
 }

src/topo.rs

@@ -1,9 +1,9 @@
 use crate::error::LexError;
 use std::{collections::VecDeque, fmt, ops::Range, str::Chars};
 
-/// The position of a specific glyph within a corpus of text. We use this for rendering error
+/// A position a some two dimensional space defined by lines and columns, specifically concerned
-/// messages and communicating to the user the location of errors.
+/// with positions of characters within text
-#[derive(Debug, PartialEq, Clone, Copy)]
+#[derive(PartialEq, Clone, Copy)]
 pub struct Position {
     /// The visual line in which this glyph appears in the source text
     pub line: u64,
@@ -13,7 +13,8 @@ pub struct Position {
 }
 
 impl Position {
-    pub fn start() -> Self {
+    /// The 0,0 position: the very first character of a document is at the 0,0 position
+    pub fn origin() -> Self {
         Self { line: 0, column: 0 }
     }
 
@@ -35,6 +36,18 @@ impl Position {
     }
 }
 
+impl fmt::Debug for Position {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
+        write!(
+            f,
+            "({line}, {column})",
+            line = self.line,
+            column = self.column
+        )
+    }
+}
+
+/// A Glyph represents a character occurring at some specific position in some input text.
 #[derive(PartialEq, Clone)]
 pub struct Glyph {
     /// the unicode code point of the glyph
@@ -50,10 +63,12 @@ pub struct Glyph {
 }
 
 impl Glyph {
+    /// checks to see whether or not the character for this glyph is a word character
     pub fn is_word(&self) -> bool {
         self.glyph.is_alphanumeric() || self.glyph == '.'
     }
 
+    /// checks to see whether or not the character for this glyph is a glob character
     pub fn is_glob(&self) -> bool {
         self.is_word() || self.glyph == '*'
     }
@@ -75,9 +90,16 @@ impl fmt::Debug for Glyph {
 /// iteration of [tokens](crate::lex::Token), Glyphs is responsible for the creation and iteration
 /// of glyphs.
 pub struct Glyphs<'text> {
+    /// the characters of the input text that we're interested in reading
     source: Chars<'text>,
+
+    /// the position of the next character in the source text
     next_position: Position,
+
+    /// the number of bytes we've read from our input document so far
     bytes_read: u64,
+
+    /// lookahead buffer
     lookahead: VecDeque<Glyph>,
 }
 
@@ -86,7 +108,7 @@ impl<'text> Glyphs<'text> {
         // neat
         Self {
             source: source.chars(),
-            next_position: Position::start(),
+            next_position: Position::origin(),
             bytes_read: 0,
             lookahead: VecDeque::new(),
         }
@@ -157,6 +179,9 @@ impl<'text> Glyphs<'text> {
         }
     }
 
+    /// discards all of the upcoming whitespace characters. After calling yeet_whitespace, the next
+    /// Glyp is guaranteed to be either non-whitespace or None (None would be because we've hit
+    /// EOF)
     pub fn yeet_whitespace(&mut self) {
         self.yeet_while(|tg| tg.glyph.is_whitespace());
     }