From 2f6f90a3310024417298db5a485ab7f0a387cd6b Mon Sep 17 00:00:00 2001
From: Yan Chen <48968912+chenyan-dfinity@users.noreply.github.com>
Date: Tue, 12 Dec 2023 10:29:49 -0800
Subject: [PATCH] refine IDLValue::Blob display (#497)

* refine IDLValue::Blob display

* fix

* fix

* fix
---
 rust/candid/src/pretty/candid.rs        | 16 ++++++++++++----
 rust/candid_parser/tests/parse_value.rs |  2 +-
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/rust/candid/src/pretty/candid.rs b/rust/candid/src/pretty/candid.rs
index ea13fe98..1e2d8439 100644
--- a/rust/candid/src/pretty/candid.rs
+++ b/rust/candid/src/pretty/candid.rs
@@ -340,8 +340,15 @@ pub mod value {
                 Opt(v) => write!(f, "opt {v:?}"),
                 Blob(b) => {
                     write!(f, "blob \"")?;
-                    for v in b.iter() {
-                        write!(f, "{}", &pp_char(*v))?;
+                    let is_ascii = b.iter().all(|c| (0x20u8..=0x7eu8).contains(c));
+                    if is_ascii {
+                        for v in b.iter() {
+                            write!(f, "{}", pp_char(*v))?;
+                        }
+                    } else {
+                        for v in b.iter() {
+                            write!(f, "\\{v:02x}")?;
+                        }
                     }
                     write!(f, "\"")
                 }
@@ -350,6 +357,7 @@ pub mod value {
                         write!(f, "blob \"")?;
                         for v in vs.iter() {
                             match v {
+                                // only here for completeness. The deserializer should generate IDLValue::Blob instead.
                                 Nat8(v) => write!(f, "{}", &pp_char(*v))?,
                                 _ => unreachable!(),
                             }
@@ -433,13 +441,13 @@ pub mod value {
     }
 
     pub fn pp_char(v: u8) -> String {
-        if (0x20..=0x7e).contains(&v) && v != 0x22 && v != 0x27 && v != 0x60 && v != 0x5c {
+        let is_ascii = (0x20u8..=0x7eu8).contains(&v);
+        if is_ascii && v != 0x22 && v != 0x27 && v != 0x60 && v != 0x5c {
             std::char::from_u32(v as u32).unwrap().to_string()
         } else {
             format!("\\{v:02x}")
         }
     }
-
     pub fn pp_value(depth: usize, v: &IDLValue) -> RcDoc {
         use IDLValue::*;
         if depth == 0 {
diff --git a/rust/candid_parser/tests/parse_value.rs b/rust/candid_parser/tests/parse_value.rs
index 589c80d5..65c23769 100644
--- a/rust/candid_parser/tests/parse_value.rs
+++ b/rust/candid_parser/tests/parse_value.rs
@@ -58,7 +58,7 @@ fn parse_string_literals() {
         ]
     );
     let args = parse_args("(blob \"DIDL\\00\\01\\7d\\80\\00\")");
-    assert_eq!(format!("{args}"), r#"(blob "DIDL\00\01}\80\00")"#);
+    assert_eq!(format!("{args}"), r#"(blob "\44\49\44\4c\00\01\7d\80\00")"#);
     let args = parse_args_err("(\"DIDL\\00\\01\\7d\\80\\00\")");
     assert_eq!(
         format!("{}", args.unwrap_err()),