pretty error (#3)

Co-authored-by: chenyan-dfinity <[email protected]>

Cargo.toml

@@ -12,6 +12,8 @@ candid = { git = "https://github.com/dfinity/candid.git", branch = "fix-beta", f
 rustyline = "8.0"
 rustyline-derive = "0.4"
 ansi_term = "0.12"
+codespan-reporting = "0.11"
+pretty = "0.10.0"
 ic-agent = { git = "https://github.com/dfinity/agent-rs.git", branch = "yan/test" }
 tokio = { version = "1.5.0", features = ["full"] }
 delay = "0.3.1"

src/command.rs

@@ -1,3 +1,4 @@
+use super::error::pretty_parse;
 use super::helper::{MyHelper, NameEnv};
 use super::token::{ParserError, Spanned, Tokenizer};
 use anyhow::{anyhow, Context};
@@ -176,7 +177,7 @@ impl Command {
                     let line_end = script.find('\n').unwrap_or(0);
                     script.drain(..line_end);
                 }
-                let cmds = script.parse::<Commands>()?;
+                let cmds = pretty_parse::<Commands>(&file, &script)?;
                 helper.base_path = path.parent().unwrap().to_path_buf();
                 for cmd in cmds.0.iter() {
                     println!("> {:?}", cmd);

src/error.rs

@@ -0,0 +1,56 @@
+use crate::token::ParserError;
+use codespan_reporting::diagnostic::{Diagnostic, Label};
+use codespan_reporting::files::SimpleFile;
+use codespan_reporting::term::{self, termcolor::StandardStream};
+
+fn report(e: &ParserError) -> Diagnostic<()> {
+    use lalrpop_util::ParseError::*;
+    let mut diag = Diagnostic::error().with_message("parser error");
+    let label = match e {
+        User { error } => Label::primary((), error.span.clone()).with_message(&error.err),
+        InvalidToken { location } => {
+            Label::primary((), *location..location + 1).with_message("Invalid token")
+        }
+        UnrecognizedEOF { location, expected } => {
+            diag = diag.with_notes(report_expected(&expected));
+            Label::primary((), *location..location + 1).with_message("Unexpected EOF")
+        }
+        UnrecognizedToken { token, expected } => {
+            diag = diag.with_notes(report_expected(&expected));
+            Label::primary((), token.0..token.2).with_message("Unexpected token")
+        }
+        ExtraToken { token } => Label::primary((), token.0..token.2).with_message("Extra token"),
+    };
+    diag.with_labels(vec![label])
+}
+
+fn report_expected(expected: &[String]) -> Vec<String> {
+    if expected.is_empty() {
+        return Vec::new();
+    }
+    use pretty::RcDoc;
+    let doc: RcDoc<()> = RcDoc::intersperse(
+        expected.iter().map(RcDoc::text),
+        RcDoc::text(",").append(RcDoc::softline()),
+    );
+    let header = if expected.len() == 1 {
+        "Expects"
+    } else {
+        "Expects one of"
+    };
+    let doc = RcDoc::text(header).append(RcDoc::softline().append(doc));
+    vec![doc.pretty(70).to_string()]
+}
+
+pub fn pretty_parse<T>(name: &str, str: &str) -> Result<T, ParserError>
+where
+    T: std::str::FromStr<Err = ParserError>,
+{
+    str.parse::<T>().map_err(|e| {
+        let writer = StandardStream::stderr(term::termcolor::ColorChoice::Auto);
+        let config = term::Config::default();
+        let file = SimpleFile::new(name, str);
+        term::emit(&mut writer.lock(), &config, &file, &report(&e)).unwrap();
+        e
+    })
+}

src/main.rs

@@ -5,10 +5,12 @@ use rustyline::CompletionType;
 use tokio::runtime::Runtime;
 
 mod command;
+mod error;
 mod grammar;
 mod helper;
 mod token;
 use crate::command::Command;
+use crate::error::pretty_parse;
 use crate::helper::MyHelper;
 
 fn unwrap<T, E, F>(v: Result<T, E>, f: F)
@@ -69,7 +71,7 @@ fn repl(opts: Opts) -> anyhow::Result<()> {
         match input {
             Ok(line) => {
                 rl.add_history_entry(&line);
-                unwrap(line.parse::<Command>(), |cmd| {
+                unwrap(pretty_parse::<Command>("stdin", &line), |cmd| {
                     let mut helper = rl.helper_mut().unwrap();
                     helper.history.push(line.clone());
                     unwrap(cmd.run(&mut helper), |_| {});