Properly escape characters, including \u200b (closes #209).

jaq-json/src/lib.rs

@@ -876,6 +876,26 @@ fn float_cmp(left: f64, right: f64) -> Ordering {
     }
 }
 
+/// Format a string as valid JSON string, including leading and trailing quotes.
+pub fn fmt_str(f: &mut fmt::Formatter, s: &str) -> fmt::Result {
+    write!(f, "\"")?;
+    for s in s.split_inclusive(|c| c < ' ' || c == '\\' || c == '"') {
+        // split s into last character and everything before (init)
+        let mut chars = s.chars();
+        let last = chars.next_back();
+        let init = chars.as_str();
+
+        match last {
+            Some(last @ ('\t' | '\n' | '\r' | '\\' | '"')) => {
+                write!(f, "{init}{}", last.escape_default())
+            }
+            Some(last) if last < ' ' => write!(f, "{init}\\u{:04x}", last as u8),
+            _ => write!(f, "{s}"),
+        }?;
+    }
+    write!(f, "\"")
+}
+
 impl fmt::Display for Val {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match self {
@@ -885,7 +905,7 @@ impl fmt::Display for Val {
             Self::Float(x) if x.is_finite() => write!(f, "{x:?}"),
             Self::Float(_) => write!(f, "null"),
             Self::Num(n) => write!(f, "{n}"),
-            Self::Str(s) => write!(f, "{s:?}"),
+            Self::Str(s) => fmt_str(f, s),
             Self::Arr(a) => {
                 write!(f, "[")?;
                 let mut iter = a.iter();

jaq-play/src/lib.rs

@@ -1,6 +1,6 @@
 use core::fmt::{self, Debug, Display, Formatter};
 use jaq_core::{compile, load, Ctx, Native, RcIter};
-use jaq_json::Val;
+use jaq_json::{fmt_str, Val};
 use wasm_bindgen::prelude::*;
 
 type Filter = jaq_core::Filter<Native<Val>>;
@@ -60,7 +60,10 @@ fn fmt_val(f: &mut Formatter, opts: &PpOpts, level: usize, v: &Val) -> fmt::Resu
         Val::Float(x) if x.is_finite() => span_dbg(f, "number", x),
         Val::Float(_) => span(f, "null", "null"),
         Val::Num(n) => span(f, "number", n),
-        Val::Str(s) => span_dbg(f, "string", escape(s)),
+        Val::Str(s) => {
+            let display = FormatterFn(|f: &mut Formatter| fmt_str(f, &escape(s)));
+            span(f, "string", display)
+        }
         Val::Arr(a) if a.is_empty() => write!(f, "[]"),
         Val::Arr(a) => {
             write!(f, "[")?;

jaq/src/main.rs

@@ -554,13 +554,8 @@ where
 fn fmt_val(f: &mut Formatter, opts: &PpOpts, level: usize, v: &Val) -> fmt::Result {
     use yansi::Paint;
     match v {
-        Val::Null => "null".fmt(f),
-        Val::Bool(b) => b.fmt(f),
-        Val::Int(i) => i.fmt(f),
-        Val::Float(x) if x.is_finite() => write!(f, "{x:?}"),
-        Val::Float(_) => "null".fmt(f),
-        Val::Num(n) => n.fmt(f),
-        Val::Str(s) => write!(f, "{:?}", s.green()),
+        Val::Null | Val::Bool(_) | Val::Int(_) | Val::Float(_) | Val::Num(_) => v.fmt(f),
+        Val::Str(_) => write!(f, "{}", v.green()),
         Val::Arr(a) => {
             '['.bold().fmt(f)?;
             if !a.is_empty() {

jaq/tests/golden.rs

@@ -83,6 +83,13 @@ test!(
 "Three""#
 );
 
+test!(
+    fmt_str,
+    &[],
+    r#""\u0000\u200b\r\t\n asdf""#,
+    r#""\u0000​\r\t\n asdf""#
+);
+
 test!(
     mods,
     &["-c", "-L", "tests", r#"include "a"; [a, data]"#],