5 ms·

My Favorite Bugs: Invalid Surrogate Pairs

101 points by meysamazad 5mo ago

jonhohle 5mo ago
Once I ran into this it became hard to treat strings “normally” in any situation or, alternatively, I’d force hard encoding requirements in the domain. Regardless, handling grapheme clusters properly is hard and easy to get wrong. I recently ported a program from python to rust and the original author used string regexes. Input and output document encoding mattered but the characters that needed to be matched were always lower ASCII. The python program could have used binary regexes, but instead forced an input encoding (UTF-8) and made the user choose an output encoding. When the input comes from an unknown process or legacy data, however, you don’t always get the luxury of assuming the encoding. Switching to binary regexes and ignoring encoding altogether simplified logic, eliminated classes of errors, and made the program work in scenarios it couldn’t earlier. Getting rid of the last decoding/encoding code gave me so much relief, especially when all of the whacky encoding tests I had already written continued to work.
- georgemandis 5mo ago
  You are reminding me we also circled an issue at one point where a backend system in Python needed to agree on the same character count length of a piece of content was the client (JavaScript). Another place Intl.Segmenter would've helped. If I'm remembering correctly, we briefly explored a solution where we told Python "This is a UTF-16LE encoded string" so the count would match, but I think we learned/realized the endianness is actually dictated by the client's machine (Going from memory here). Ultimately we just changed the solution so the client was the source of truth about lengths and counts. These threads are surfacing all kinds of things I forgot about and didn't add in that blog post. Maybe I need to write another, haha.
skybrian 5mo ago
Writing property tests on functions that work with strings is a good way to find lots of Unicode issues.
wupatz 5mo ago
it's good to know about surrogate pairs in unicode. It was new to me too when being part of tracking down incomplete unicode flags in the (excellent) phanpy mastodon client. Author went for Intl.Segmenter too: https://github.com/cheeaun/phanpy/issues/1491 https://github.com/cheeaun/phanpy/issues/1491
- georgemandis 5mo ago
  My recollection (that I didn't add to the story): I don't think Intl.Segmenter had great browser support then (2022). Even if it had it still wasn't a quick/obvious fix for our problem with where it was occurring in our stack. But I do remember looking at it then.
georgemandis 5mo ago
Just noticed this is getting some traffic! It's a little buried in the post, but I made an interactive tool for exploring surrogate pairs as part of this: - https://george.mand.is/invalid-surrogate-pairs/ https://george.mand.is/invalid-surrogate-pairs/ I thought it was something that's easier to play with and feel than necessarily just read about.
BobbyTables2 5mo ago
Damn, I’ve never really had to deal with Unicode all that much. Was already bad enough that instead of bytes, we have to worry about code points. Now even that isn’t enough? It would have been expensive, but all characters should have been fixed size 64bit values.
- chuckadams 5mo ago
  > It would have been expensive, but all characters should have been fixed size 64bit values. It would have been a non-starter, and then we'd all be dealing with Shift-JIS, BIG5, and FSM knows how many different codepages to this day. UTF-8 is about as elegant as it gets, though Java and JS still managed to fuck that up too (they both encode every codepoint outside the BMP as surrogate pairs in UTF-8)
  - dasyatidprime 5mo ago
    That's called CESU-8. https://www.unicode.org/reports/tr26/tr26-4.html https://www.unicode.org/reports/tr26/tr26-4.html
  - chrismorgan 5mo ago
    > Java and JS […] both encode every codepoint outside the BMP as surrogate pairs in UTF-8 I can’t comment on Java, but JS I know reasonably well and I can’t think of any place it uses CESU-8.
    - layer8 5mo ago
      Java doesn’t either.
- usrnm 5mo ago
  > It would have been expensive, but all characters should have been fixed size 64bit values You're making the same mistake that numerous people made before you: thinking that it's as simple as using arrays of large enough numbers. First they thought that two bytes per symbol would be enough, then four. Spoiler alert: it wasn't. And eight won't work either.
agus4nas 5mo ago
Great write-up. Do most modern languages handle invalid surrogates gracefully, or is it still a "good luck" situation depending on the runtime?
- amluto 5mo ago
  Modern string libraries largely use UTF-8 [0], and surrogates, regardless of whether they’re paired, are invalid in UTF-8. So, in a modern string library, as built in to most modern languages, you will not encounter surrogates except when translating between encodings. [0] But everyone disagrees as to what indexing a string means, so you need to make an actual choice if you want anything involving indexing to match across languages.
  - chuckadams 5mo ago
    > surrogates, regardless of whether they’re paired, are invalid in UTF-8 Java did not get the memo. Since the char type is fixed at 16 bits, it uses surrogates to encode everything outside the BMP, regardless of the encoding.
    - shawn_w 5mo ago
      If you use the string methods that work with code points instead of chars, you rarely if ever have to deal with surrogate pairs in Java.
- georgemandis 5mo ago
  The language handled it fine. It will generally just show replacement characters (�) for combos that don't map to anything. It was really `encodeURIComponent` that didn't handle it gracefully. If you just type this into the console (surrogate pair for cowboy smiley face emoji), you see it encodes it ("%F0%9F%A4%A0"): encodeURIComponent("\uD83E\uDD20") If you give it an invalid surrogate pair, it will throw an actual error: encodeURIComponent("\uDD20\uD83E")
  - chrismorgan 5mo ago
impure 5mo ago
I had an emoji cut in half problem in Dart. I was a bit surprised because I thought substring operations worked on characters. It only caused an invalid Unicode symbol though so not too bad.
- tialaramex 5mo ago
  > I thought substring operations worked on characters "character" turns out to be too vague an idea to correspond to some specific fact about the software. If you co-worker says his Uncle is "conservative" does he mean like "Believes Right To Work laws are a good idea" conservative or "Believes Joe Biden is a Communist" conservative ? https://en.wikipedia.org/wiki/Character_(symbol) https://en.wikipedia.org/wiki/Character_(symbol) gives you some idea about this rabbit hole. Suffice to say, no, you can't have operations on "characters" until you've nailed down exactly what it was you meant by that.
bombela 5mo ago
In summary, Unicode code points (characters) are 32 bit. JavaScript manipulates Unicode in utf-16 for historical reasons, because at some point before Unicode, 16 bit was deemed enough (ucs-2). utf-16 run length encodes Unicode 32 codepoints into one or two code units. Splitting in a middle of a codepoints produces one invalid half string, and one semantically different half string. emojies are a sequence of Unicode codepoints producing a single grapheme. Splitting in the middle of a grapheme will produce two valid strings, but with some funky half baked emoji. So for a text editor it makes sense to split between grapheme boundaries.
- chrismorgan 5mo ago
  > Unicode code points are 32 bit 21-bit, actually. It was supposed to be 32-bit, but UTF-16 caps out at 21-bit, so they lopped eleven bits of potential from Unicode (and UTF-8, so no more six-byte encoding). > at some point before Unicode No, in the early days of Unicode. > run length encodes Um… what? RLE is a data compression thing, UTF-16 has nothing to do with it.
  - Someone 5mo ago
    >> Unicode code points are 32 bit > 21-bit, actually Less than that. https://en.wikipedia.org/wiki/Code_point#In_character_encoding https://en.wikipedia.org/wiki/Code_point#In_character_encodi...: “The Unicode code space is divided into seventeen planes (the basic multilingual plane, and 16 supplementary planes), each with 65,536 (= 2¹⁶) code points. Thus the total size of the Unicode code space is 17 × 65,536 = 1,114,112” That makes it log(1,114,112)/log(2) bit. That’s about 20,09. (https://www.unicode.org/versions/Unicode17.0.0/ https://www.unicode.org/versions/Unicode17.0.0/ assigns 159,801 of them to characters)
    - bombela 5mo ago
      Don't know what you are being down voted (or my grand parent comment for that matter). You are very correct.
    - chrismorgan 5mo ago
chrismorgan 5mo ago
A CRDT library working at the code unit level? Ouch. Of course that’s going to go wrong, it was inevitable. As for using extended grapheme clusters, it sounds a little bit iffy—maybe possible to use correctly, maybe not, because they’re not stable over time. That style of thing has created some fascinating bugs, like (a few years ago) index corruption in PostgreSQL due to collation changes. Unicode scalar values are technically-safe: you can’t introduce invalid Unicode. But you can definitely still end up with nonsense. > We made emoji an atomic node type. That avoids problems for emoji, but leaves the underlying hazard untouched. I imagine it could still theoretically occur with other text, probably CJK. But probably only theoretically. > This splits by grapheme clusters rather than code units. No orphaned surrogates, no split emoji. It's what .slice() should have been doing all along, but of course UTF-16 predates emoji by decades. I do not agree that slice() should operate on extended grapheme clusters. Don’t lump the grapheme cluster/scalar value split in with the sins of UTF-16 and its unreliable code point/code unit split. UTF-16 was unforced error (and I still can’t work out why it wasn’t obvious from the start that UCS-2 would never be enough). But the concept of multiple scalars contributing to the logical unit was always inevitable.
- georgemandis 5mo ago
  >I do not agree that slice() should operate on extended grapheme clusters. Don’t lump the grapheme cluster/scalar value split in with the sins of UTF-16 and its unreliable code point/code unit split. Yeah, I think that's fair. I didn't really think this through as I was writing it. I'm not even so sure "ending up with nonsense" here is the worst outcome. It might be unavoidable with this approach and if that had been the only problem this bug might have been less memorable. The real problem—which I mention didn't articulate/emphasize particularly well—was that these invalid surrogate pairs were getting passed into `encodeURIComponent` somewhere deep in the stack and choking catastrophically on them. That was the "real" bug at the end of the day, but the invalid surrogate pairs and the way they were getting created on the way were a fun journey to untangle.
- rectang 5mo ago
  > I still can’t work out why it wasn’t obvious from the start that UCS-2 would never be enough) Surely certain people did know, but those people weren't in a position to do anything about it. Specifically, there were surely people who knew that because historical Chinese place names, Japanese nicknames, and so on, were not included in the original "Unicode" (it wasn't called UCS-2 yet) it was insufficient for complete expression of Asian languages. There were also many people who objected to Han unification, which is a different problem. But all of these objections were discarded because of the overwhelming mandate for a fixed-width encoding. The original "Unicode" was conceived as a "16-bit" initiative. Its 16-bit-ness was an essential aspect of the design and the Unicode Consortium did what they had to do to fit all scripts and characters "in modern use" into 16 bits. From the Wikipedia article on Han Unification[1]: > Some of the controversy stems from the fact that the very decision of performing Han unification was made by the initial Unicode Consortium, which at the time was a consortium of North American companies and organizations (most of them in California), but included no East Asian government representatives. The initial design goal was to create a 16-bit standard, and Han unification was therefore a critical step for avoiding tens of thousands of character duplications. [1] https://en.wikipedia.org/wiki/Han_unification https://en.wikipedia.org/wiki/Han_unification
Dwedit 5mo ago
Windows allows unmatched surrogate pairs in filenames, invalid for UTF-16. Likewise, Linux allows invalid UTF-8 byte sequences in filenames. Because invalid UTF-16 strings could show up in places within Windows, someone made a UTF-8 variant called "WTF-8", which allows unmatched surrogate pairs to survive a round trip.
- bombela 5mo ago
  Indeed, Linux allows anything but "/" and "\0" in filenames. Those days its reasonable to refuse utf8 filenames. But one must always validate first!
  - mananaysiempre 5mo ago
    > Indeed, Linux allows anything but "/" and "\0" in filenames. For what it’s worth, NT allows any 16-bit quantity but L'\\' (0x005C) in filenames (even nulls); it’s the Win32 layer on top of it that imposes all the other weird restrictions and mappings.
    - Dwedit 5mo ago
      The NT Object Namespace itself indeed has no restrictions on filename characters except for "\", but once you reach a real filesystem like NTFS or FAT, the forbidden characters continue to be blocked. https://projectzero.google/2016/02/the-definitive-guide-on-win32-to-nt.html https://projectzero.google/2016/02/the-definitive-guide-on-w...
dimes 5mo ago
I have a similar, Unicode-related “favorite bug”. We were expanding our product to a new language that used non-ASCII code points. Part of the system involved invoking binaries using text as input. Locally, everything worked great. Once deployed, we got corrupted text output. As soon as we SSH’d on to the server to inspect, everything started working again. It turns out that SSH servers can modify the LANG environment variable. The default value on our servers didn’t support Unicode, but LANG was updated as soon as we connected via ssh. It was a head scratcher for sure.
vishnuharidas 5mo ago
And here's a UTF-8 Playground: https://utf8-playground.netlify.app https://utf8-playground.netlify.app
raymondchau 5mo ago
[flagged]
denzen 5mo ago
I hit a similar problem in an application that was performing non-unicode-aware string operations on user-submitted text in a typescript codebase. The data couldn't be processed by an external service that was expecting valid Unicode. My fix was using toWellFormed: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/toWellFormed https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...
frizlab 5mo ago
One of the reasons why I love Swift. It has proper, unescapable Unicode String support.

101 points by meysamazad 5mo ago

Once I ran into this it became hard to treat strings “normally” in any situation or, alternatively, I’d force hard encoding requirements in the domain. Regardless, handling grapheme clusters properly is hard and easy to get wrong. I recently ported a program from python to rust and the original author used string regexes. Input and output document encoding mattered but the characters that needed to be matched were always lower ASCII. The python program could have used binary regexes, but instead forced an input encoding (UTF-8) and made the user choose an output encoding. When the input comes from an unknown process or legacy data, however, you don’t always get the luxury of assuming the encoding. Switching to binary regexes and ignoring encoding altogether simplified logic, eliminated classes of errors, and made the program work in scenarios it couldn’t earlier. Getting rid of the last decoding/encoding code gave me so much relief, especially when all of the whacky encoding tests I had already written continued to work.

georgemandis 5mo ago
You are reminding me we also circled an issue at one point where a backend system in Python needed to agree on the same character count length of a piece of content was the client (JavaScript). Another place Intl.Segmenter would've helped. If I'm remembering correctly, we briefly explored a solution where we told Python "This is a UTF-16LE encoded string" so the count would match, but I think we learned/realized the endianness is actually dictated by the client's machine (Going from memory here). Ultimately we just changed the solution so the client was the source of truth about lengths and counts. These threads are surfacing all kinds of things I forgot about and didn't add in that blog post. Maybe I need to write another, haha.

skybrian 5mo ago

Writing property tests on functions that work with strings is a good way to find lots of Unicode issues.

wupatz 5mo ago

it's good to know about surrogate pairs in unicode. It was new to me too when being part of tracking down incomplete unicode flags in the (excellent) phanpy mastodon client. Author went for Intl.Segmenter too: https://github.com/cheeaun/phanpy/issues/1491 https://github.com/cheeaun/phanpy/issues/1491

georgemandis 5mo ago
My recollection (that I didn't add to the story): I don't think Intl.Segmenter had great browser support then (2022). Even if it had it still wasn't a quick/obvious fix for our problem with where it was occurring in our stack. But I do remember looking at it then.

georgemandis 5mo ago

Just noticed this is getting some traffic! It's a little buried in the post, but I made an interactive tool for exploring surrogate pairs as part of this: - https://george.mand.is/invalid-surrogate-pairs/ https://george.mand.is/invalid-surrogate-pairs/ I thought it was something that's easier to play with and feel than necessarily just read about.

BobbyTables2 5mo ago

Damn, I’ve never really had to deal with Unicode all that much. Was already bad enough that instead of bytes, we have to worry about code points. Now even that isn’t enough? It would have been expensive, but all characters should have been fixed size 64bit values.

chuckadams 5mo ago
> It would have been expensive, but all characters should have been fixed size 64bit values. It would have been a non-starter, and then we'd all be dealing with Shift-JIS, BIG5, and FSM knows how many different codepages to this day. UTF-8 is about as elegant as it gets, though Java and JS still managed to fuck that up too (they both encode every codepoint outside the BMP as surrogate pairs in UTF-8)
- dasyatidprime 5mo ago
  That's called CESU-8. https://www.unicode.org/reports/tr26/tr26-4.html https://www.unicode.org/reports/tr26/tr26-4.html
- chrismorgan 5mo ago
  > Java and JS […] both encode every codepoint outside the BMP as surrogate pairs in UTF-8 I can’t comment on Java, but JS I know reasonably well and I can’t think of any place it uses CESU-8.
  - layer8 5mo ago
    Java doesn’t either.
usrnm 5mo ago
> It would have been expensive, but all characters should have been fixed size 64bit values You're making the same mistake that numerous people made before you: thinking that it's as simple as using arrays of large enough numbers. First they thought that two bytes per symbol would be enough, then four. Spoiler alert: it wasn't. And eight won't work either.

agus4nas 5mo ago

Great write-up. Do most modern languages handle invalid surrogates gracefully, or is it still a "good luck" situation depending on the runtime?

amluto 5mo ago
Modern string libraries largely use UTF-8 [0], and surrogates, regardless of whether they’re paired, are invalid in UTF-8. So, in a modern string library, as built in to most modern languages, you will not encounter surrogates except when translating between encodings. [0] But everyone disagrees as to what indexing a string means, so you need to make an actual choice if you want anything involving indexing to match across languages.
- chuckadams 5mo ago
  > surrogates, regardless of whether they’re paired, are invalid in UTF-8 Java did not get the memo. Since the char type is fixed at 16 bits, it uses surrogates to encode everything outside the BMP, regardless of the encoding.
  - shawn_w 5mo ago
    If you use the string methods that work with code points instead of chars, you rarely if ever have to deal with surrogate pairs in Java.
georgemandis 5mo ago
The language handled it fine. It will generally just show replacement characters (�) for combos that don't map to anything. It was really `encodeURIComponent` that didn't handle it gracefully. If you just type this into the console (surrogate pair for cowboy smiley face emoji), you see it encodes it ("%F0%9F%A4%A0"): encodeURIComponent("\uD83E\uDD20") If you give it an invalid surrogate pair, it will throw an actual error: encodeURIComponent("\uDD20\uD83E")
- chrismorgan 5mo ago

impure 5mo ago

I had an emoji cut in half problem in Dart. I was a bit surprised because I thought substring operations worked on characters. It only caused an invalid Unicode symbol though so not too bad.

tialaramex 5mo ago
> I thought substring operations worked on characters "character" turns out to be too vague an idea to correspond to some specific fact about the software. If you co-worker says his Uncle is "conservative" does he mean like "Believes Right To Work laws are a good idea" conservative or "Believes Joe Biden is a Communist" conservative ? https://en.wikipedia.org/wiki/Character_(symbol) https://en.wikipedia.org/wiki/Character_(symbol) gives you some idea about this rabbit hole. Suffice to say, no, you can't have operations on "characters" until you've nailed down exactly what it was you meant by that.

bombela 5mo ago

In summary, Unicode code points (characters) are 32 bit. JavaScript manipulates Unicode in utf-16 for historical reasons, because at some point before Unicode, 16 bit was deemed enough (ucs-2). utf-16 run length encodes Unicode 32 codepoints into one or two code units. Splitting in a middle of a codepoints produces one invalid half string, and one semantically different half string. emojies are a sequence of Unicode codepoints producing a single grapheme. Splitting in the middle of a grapheme will produce two valid strings, but with some funky half baked emoji. So for a text editor it makes sense to split between grapheme boundaries.

chrismorgan 5mo ago
> Unicode code points are 32 bit 21-bit, actually. It was supposed to be 32-bit, but UTF-16 caps out at 21-bit, so they lopped eleven bits of potential from Unicode (and UTF-8, so no more six-byte encoding). > at some point before Unicode No, in the early days of Unicode. > run length encodes Um… what? RLE is a data compression thing, UTF-16 has nothing to do with it.
- Someone 5mo ago
  >> Unicode code points are 32 bit > 21-bit, actually Less than that. https://en.wikipedia.org/wiki/Code_point#In_character_encoding https://en.wikipedia.org/wiki/Code_point#In_character_encodi...: “The Unicode code space is divided into seventeen planes (the basic multilingual plane, and 16 supplementary planes), each with 65,536 (= 2¹⁶) code points. Thus the total size of the Unicode code space is 17 × 65,536 = 1,114,112” That makes it log(1,114,112)/log(2) bit. That’s about 20,09. (https://www.unicode.org/versions/Unicode17.0.0/ https://www.unicode.org/versions/Unicode17.0.0/ assigns 159,801 of them to characters)
  - bombela 5mo ago
    Don't know what you are being down voted (or my grand parent comment for that matter). You are very correct.
  - chrismorgan 5mo ago

chrismorgan 5mo ago

A CRDT library working at the code unit level? Ouch. Of course that’s going to go wrong, it was inevitable. As for using extended grapheme clusters, it sounds a little bit iffy—maybe possible to use correctly, maybe not, because they’re not stable over time. That style of thing has created some fascinating bugs, like (a few years ago) index corruption in PostgreSQL due to collation changes. Unicode scalar values are technically-safe: you can’t introduce invalid Unicode. But you can definitely still end up with nonsense. > We made emoji an atomic node type. That avoids problems for emoji, but leaves the underlying hazard untouched. I imagine it could still theoretically occur with other text, probably CJK. But probably only theoretically. > This splits by grapheme clusters rather than code units. No orphaned surrogates, no split emoji. It's what .slice() should have been doing all along, but of course UTF-16 predates emoji by decades. I do not agree that slice() should operate on extended grapheme clusters. Don’t lump the grapheme cluster/scalar value split in with the sins of UTF-16 and its unreliable code point/code unit split. UTF-16 was unforced error (and I still can’t work out why it wasn’t obvious from the start that UCS-2 would never be enough). But the concept of multiple scalars contributing to the logical unit was always inevitable.

georgemandis 5mo ago
>I do not agree that slice() should operate on extended grapheme clusters. Don’t lump the grapheme cluster/scalar value split in with the sins of UTF-16 and its unreliable code point/code unit split. Yeah, I think that's fair. I didn't really think this through as I was writing it. I'm not even so sure "ending up with nonsense" here is the worst outcome. It might be unavoidable with this approach and if that had been the only problem this bug might have been less memorable. The real problem—which I mention didn't articulate/emphasize particularly well—was that these invalid surrogate pairs were getting passed into `encodeURIComponent` somewhere deep in the stack and choking catastrophically on them. That was the "real" bug at the end of the day, but the invalid surrogate pairs and the way they were getting created on the way were a fun journey to untangle.
rectang 5mo ago
> I still can’t work out why it wasn’t obvious from the start that UCS-2 would never be enough) Surely certain people did know, but those people weren't in a position to do anything about it. Specifically, there were surely people who knew that because historical Chinese place names, Japanese nicknames, and so on, were not included in the original "Unicode" (it wasn't called UCS-2 yet) it was insufficient for complete expression of Asian languages. There were also many people who objected to Han unification, which is a different problem. But all of these objections were discarded because of the overwhelming mandate for a fixed-width encoding. The original "Unicode" was conceived as a "16-bit" initiative. Its 16-bit-ness was an essential aspect of the design and the Unicode Consortium did what they had to do to fit all scripts and characters "in modern use" into 16 bits. From the Wikipedia article on Han Unification[1]: > Some of the controversy stems from the fact that the very decision of performing Han unification was made by the initial Unicode Consortium, which at the time was a consortium of North American companies and organizations (most of them in California), but included no East Asian government representatives. The initial design goal was to create a 16-bit standard, and Han unification was therefore a critical step for avoiding tens of thousands of character duplications. [1] https://en.wikipedia.org/wiki/Han_unification https://en.wikipedia.org/wiki/Han_unification

Dwedit 5mo ago

Windows allows unmatched surrogate pairs in filenames, invalid for UTF-16. Likewise, Linux allows invalid UTF-8 byte sequences in filenames. Because invalid UTF-16 strings could show up in places within Windows, someone made a UTF-8 variant called "WTF-8", which allows unmatched surrogate pairs to survive a round trip.

bombela 5mo ago
Indeed, Linux allows anything but "/" and "\0" in filenames. Those days its reasonable to refuse utf8 filenames. But one must always validate first!
- mananaysiempre 5mo ago
  > Indeed, Linux allows anything but "/" and "\0" in filenames. For what it’s worth, NT allows any 16-bit quantity but L'\\' (0x005C) in filenames (even nulls); it’s the Win32 layer on top of it that imposes all the other weird restrictions and mappings.
  - Dwedit 5mo ago
    The NT Object Namespace itself indeed has no restrictions on filename characters except for "\", but once you reach a real filesystem like NTFS or FAT, the forbidden characters continue to be blocked. https://projectzero.google/2016/02/the-definitive-guide-on-win32-to-nt.html https://projectzero.google/2016/02/the-definitive-guide-on-w...

dimes 5mo ago

I have a similar, Unicode-related “favorite bug”. We were expanding our product to a new language that used non-ASCII code points. Part of the system involved invoking binaries using text as input. Locally, everything worked great. Once deployed, we got corrupted text output. As soon as we SSH’d on to the server to inspect, everything started working again. It turns out that SSH servers can modify the LANG environment variable. The default value on our servers didn’t support Unicode, but LANG was updated as soon as we connected via ssh. It was a head scratcher for sure.

vishnuharidas 5mo ago

And here's a UTF-8 Playground: https://utf8-playground.netlify.app https://utf8-playground.netlify.app

raymondchau 5mo ago

[flagged]

denzen 5mo ago

I hit a similar problem in an application that was performing non-unicode-aware string operations on user-submitted text in a typescript codebase. The data couldn't be processed by an external service that was expecting valid Unicode. My fix was using toWellFormed: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/toWellFormed https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...

frizlab 5mo ago

One of the reasons why I love Swift. It has proper, unescapable Unicode String support.