first pass at pretty-printing parser errors

2 files changed, 61 insertions, 1 deletions

diff --git a/src/bin/mt-tool.rs b/src/bin/mt-tool.rs
index 03f590a..61db3fe 100644
--- a/src/bin/mt-tool.rs
+++ b/src/bin/mt-tool.rs
@@ -31,7 +31,7 @@ fn parse_modelica_files(paths: Vec<String>) {
 
         match result {
             Ok(_) => println!("Input `{}` ({}s): OK", input, elapsed),
-            Err(err) => println!("Input `{}` ({}s): parse error {:?}", input, elapsed, err),
+            Err(err) => println!("Input `{}` ({}sec): ERROR\n{}", input, elapsed, modelthing::pp_parseerror(&s, err)),
         }
     }
 }
diff --git a/src/lib.rs b/src/lib.rs
index c733dc7..3f6021d 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -3,6 +3,8 @@
 extern crate log;
 
 extern crate toml;
+extern crate colored;
+extern crate lalrpop_util;
 
 pub mod modelica_parser;
 pub mod modelica_ast;
@@ -14,6 +16,9 @@ use std::fs;
 use std::io::Read;
 use std::fs::File;
 
+use lalrpop_util::ParseError;
+use colored::*;
+
 #[derive(Debug, PartialEq)]
 pub struct ModelMetadata {
     pub name_en: String,
@@ -119,6 +124,61 @@ pub fn search_models(p: &Path) -> Vec<String> {
     }
 }
 
+fn pp_segment(raw: &str, start: usize, end: usize) -> String {
+    let mut line_start = 0;
+    let mut num = 0;
+    let mut ret = String::new();
+    for line in raw.lines() {
+        num += 1;
+        let line_end = line_start + line.len();
+        if (line_start <= start) && (start < line_end) {
+            ret += &format!("    {}\n{:>3} {} {}{}{}\n    {} {}{}\n",
+                "|".blue().bold(),
+                num.to_string().blue().bold(),
+                "|".blue().bold(),
+                raw[line_start..start].normal(),
+                raw[start..end].red().bold(),
+                if end < line_end {
+                    raw[end..line_end].normal()
+                } else {
+                    "".normal()
+                },
+                "|".blue().bold(),
+                std::iter::repeat(" ").take(start - line_start).collect::<String>(),
+                std::iter::repeat("^").take(end - start).collect::<String>().red().bold());
+        }
+        line_start += line.len() + 1;
+        if line_start > end { break };
+    }
+    ret
+}
+
+pub fn pp_parseerror(raw: &str, pe: ParseError<usize, (usize, &str), ()>) -> String {
+    match pe {
+        ParseError::InvalidToken{location} => {
+            format!("{} invalid token starting at:\n{}",
+                "parse error:".red().bold(),
+                pp_segment(raw, location, location+1)) },
+        ParseError::UnrecognizedToken{token: Some((start, (_, tok), end)), expected} => {
+            format!("{} unrecognized token '{}' (expected one of {:?}):\n{}",
+                "parse error:".red().bold(),
+                tok,
+                expected,
+                pp_segment(raw, start, end)) },
+        ParseError::UnrecognizedToken{token: None, expected} => {
+            format!("{} premature end-of-file (expected one of {:?})",
+                "parse error:".red().bold(),
+                expected) },
+        ParseError::ExtraToken{token: (start, (_, tok), end)} => {
+            format!("{} unexpected extra token '{}':\n{}",
+                "parse error:".red().bold(),
+                tok,
+                pp_segment(raw, start, end)) },
+        _ => {
+            format!("{} {:?}", "parse error:".red().bold(), pe) },
+    }
+}
+
 /* ******************************** Tests ******************************* */
 
 #[test]