Fix error messages with wide character

Input may contain tabs and other characters whose byte widths do not
correspond to their display widths. This causes error context
underlining to be off when lines contain those characters

Fixed by properly accounting for the display width of characters, as
well as replacing tabs with spaces when printing error messages.

Cargo.lock

@@ -10,6 +10,7 @@ dependencies = [
  "lazy_static 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "regex 0.1.80 (registry+https://github.com/rust-lang/crates.io-index)",
  "tempdir 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "unicode-width 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]

Cargo.toml

@@ -15,3 +15,4 @@ itertools   = "^0.5.5"
 lazy_static   = "^0.2.1"
 regex         = "^0.1.77"
 tempdir       = "^0.3.5"
+unicode-width = "^0.1.3"

justfile

@@ -50,6 +50,9 @@ nop:
 fail:
 	exit 1
 
+backtick-fail:
+	echo {{`exit 1`}}
+
 # make a quine, compile it, and verify it
 quine: create
 	cc tmp/gen0.c -o tmp/gen0

src/integration.rs

@@ -372,6 +372,96 @@ fn backtick_code_interpolation() {
   );
 }
 
+#[test]
+fn backtick_code_interpolation_tab() {
+  integration_test(
+    &[],
+    "
+backtick-fail:
+\techo {{`exit 1`}}
+",
+    1,
+    "",
+    "error: backtick failed with exit code 1
+  |
+3 |     echo {{`exit 1`}}
+  |            ^^^^^^^^
+",
+  );
+}
+
+#[test]
+fn backtick_code_interpolation_tabs() {
+  integration_test(
+    &[],
+    "
+backtick-fail:
+\techo {{\t`exit 1`}}
+",
+    1,
+    "",
+    "error: backtick failed with exit code 1
+  |
+3 |     echo {{    `exit 1`}}
+  |                ^^^^^^^^
+",
+  );
+}
+
+#[test]
+fn backtick_code_interpolation_inner_tab() {
+  integration_test(
+    &[],
+    "
+backtick-fail:
+\techo {{\t`exit\t\t1`}}
+",
+    1,
+    "",
+    "error: backtick failed with exit code 1
+  |
+3 |     echo {{    `exit        1`}}
+  |                ^^^^^^^^^^^^^^^
+",
+  );
+}
+
+#[test]
+fn backtick_code_interpolation_leading_emoji() {
+  integration_test(
+    &[],
+    "
+backtick-fail:
+\techo 😬{{`exit 1`}}
+",
+    1,
+    "",
+    "error: backtick failed with exit code 1
+  |
+3 |     echo 😬{{`exit 1`}}
+  |             ^^^^^^^^
+",
+  );
+}
+
+#[test]
+fn backtick_code_interpolation_unicode_hell() {
+  integration_test(
+    &[],
+    "
+backtick-fail:
+\techo \t\t\t😬鎌鼬{{\t\t`exit 1 # \t\t\t😬鎌鼬`}}\t\t\t😬鎌鼬
+",
+    1,
+    "",
+    "error: backtick failed with exit code 1
+  |
+3 |     echo             😬鎌鼬{{        `exit 1 #             😬鎌鼬`}}            😬鎌鼬
+  |                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+",
+  );
+}
+
 #[test]
 fn backtick_code_long() {
   integration_test(

src/lib.rs

@@ -14,6 +14,7 @@ extern crate regex;
 extern crate tempdir;
 extern crate itertools;
 extern crate ansi_term;
+extern crate unicode_width;
 
 use std::io::prelude::*;
 
@@ -786,12 +787,41 @@ fn write_error_context(
   let red = maybe_red(f.alternate());
   match text.lines().nth(line) {
     Some(line) => {
+      let mut i = 0;
+      let mut space_column = 0;
+      let mut space_line   = String::new();
+      let mut space_width  = 0;
+      for c in line.chars() {
+        if c == '\t' {
+          space_line.push_str("    ");
+          if i < column {
+            space_column += 4;
+          }
+          if i >= column && i < column + width.unwrap_or(1) {
+            space_width += 4;
+          }
+        } else {
+          if i < column {
+            space_column += unicode_width::UnicodeWidthChar::width(c).unwrap_or(0);
+
+          }
+          if i >= column && i < column + width.unwrap_or(1) {
+            space_width += unicode_width::UnicodeWidthChar::width(c).unwrap_or(0);
+          }
+          space_line.push(c);
+        }
+        i += c.len_utf8();
+      }
       let line_number_width = line_number.to_string().len();
       try!(write!(f, "{0:1$} |\n", "", line_number_width));
-      try!(write!(f, "{} | {}\n", line_number, line));
+      try!(write!(f, "{} | {}\n", line_number, space_line));
       try!(write!(f, "{0:1$} |", "", line_number_width));
-      try!(write!(f, " {0:1$}{2}{3:^<4$}{5}", "", column,
+      if width == None {
-                  red.prefix(), "", width.unwrap_or(1), red.suffix()));
+        try!(write!(f, " {0:1$}{2}^{3}", "", space_column, red.prefix(), red.suffix()));
+      } else {
+        try!(write!(f, " {0:1$}{2}{3:^<4$}{5}", "", space_column,
+                    red.prefix(), "", space_width, red.suffix()));
+      }
     },
     None => if index != text.len() {
       try!(write!(f, "internal error: Error has invalid line number: {}", line_number))
@@ -1091,7 +1121,10 @@ enum RunError<'a> {
 impl<'a> Display for RunError<'a> {
   fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
     let red = maybe_red(f.alternate());
-    try!(write!(f, "{} ", red.paint("error:")));
+    let bold = maybe_bold(f.alternate());
+    try!(write!(f, "{} {}", red.paint("error:"), bold.prefix()));
+
+    let mut error_token = None;
 
     match *self {
       RunError::UnknownRecipes{ref recipes} => {
@@ -1140,15 +1173,15 @@ impl<'a> Display for RunError<'a> {
                     recipe, io_error)),
       RunError::BacktickCode{code, ref token} => {
         try!(write!(f, "backtick failed with exit code {}\n", code));
-        try!(write_token_error_context(f, token));
+        error_token = Some(token);
       }
       RunError::BacktickSignal{ref token, signal} => {
         try!(write!(f, "backtick was terminated by signal {}", signal));
-        try!(write_token_error_context(f, token));
+        error_token = Some(token);
       }
       RunError::BacktickUnknownFailure{ref token} => {
         try!(write!(f, "backtick failed for an uknown reason"));
-        try!(write_token_error_context(f, token));
+        error_token = Some(token);
       }
       RunError::BacktickIoError{ref token, ref io_error} => {
         try!(match io_error.kind() {
@@ -1160,11 +1193,11 @@ impl<'a> Display for RunError<'a> {
           _ => write!(f, "backtick could not be run because of an IO \
                           error while launching `sh`:\n{}", io_error),
         });
-        try!(write_token_error_context(f, token));
+        error_token = Some(token);
       }
       RunError::BacktickUtf8Error{ref token, ref utf8_error} => {
         try!(write!(f, "backtick succeeded but stdout was not utf8: {}", utf8_error));
-        try!(write_token_error_context(f, token));
+        error_token = Some(token);
       }
       RunError::InternalError{ref message} => {
         try!(write!(f, "internal error, this may indicate a bug in just: {}
@@ -1172,6 +1205,12 @@ consider filing an issue: https://github.com/casey/just/issues/new", message));
       }
     }
 
+    try!(write!(f, "{}", bold.suffix()));
+
+    if let Some(token) = error_token {
+      try!(write_token_error_context(f, token));
+    }
+
     Ok(())
   }
 }