formatjs icu message syntax error unexpected token

Not specified by the original author.

Fix the formatjs ICU message syntax error on an unexpected token

TL;DR

The ICU parser hit a character it did not expect at a specific offset, so get that offset and look there first. The usual suspects are a stray apostrophe, which starts quoted text in ICU, or a brace that never closes. Fix the character, re-parse, and move on.

The error

SyntaxError: Unexpected token at offset 24
message: "You\u0027ve got {count, plural, one {# message} other {# messages}}"
the doubled quote above is the correct escape, a single quote breaks parsing

Fix it

Step 1: Reproduce the parse failure with the exact string

node -e "const {parse}=require('@formatjs/icu-messageformat-parser'); parse(process.argv[1])" "You've got {count, plural, one {# message} other {# messages}}"

Expected: The parser throws and names the offset.

Step 2: Inspect the character at that offset

node -e "const s=process.argv[1]; const i=24; console.log(JSON.stringify(s.slice(i-6,i+6)))" "You've got {count, plural, one {# message} other {# messages}}"

Expected: You see the offending character in context.

Step 3: Fix it: double apostrophes, balance braces

node -e "console.log('write You\u0027\u0027ve for a literal apostrophe in ICU')"

Expected: The corrected string parses cleanly.

Step 4: Add the message to your extract lint so it stays fixed

npx formatjs extract 'src/**/*.js' --out-file /tmp/check.json | tail -3

Expected: Extraction completes with no syntax errors.

When to use this

• formatjs throws SyntaxError or unexpected token while parsing a message
• A message with apostrophes or quotes fails to parse

When NOT to use this

• The message parses but selects the wrong plural, check locale data
• The error is at runtime in the browser, make sure the parser version matches the runtime

Tool and version compatibility

• @formatjs/icu-messageformat-parser v1/v2, react-intl v5+
• ICU MessageFormat as implemented by formatjs, not Java MessageFormat

Variant phrasings

unexpected token inside a select block

Same approach. Select blocks need an other case, a missing one often reads as an unexpected token at the end.

error only in one locale file

Translators edited the ICU syntax. Diff that locale against the source message and fix the syntax there.

Why it happens

ICU gives special meaning to apostrophes, braces, and the # sign. A translator typing a normal apostrophe accidentally opens a quoted section that never closes, and the parser reports the spot where the grammar stops making sense.

Edge cases

• Smart quotes from word processors are not ICU quotes, normalize to straight quotes first
• The # sign outside a plural case is literal in some versions and an error in others, avoid it
• Argument names are case sensitive, count and Count are different arguments

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_fxBHwFmd-Au2bqNIvu0rGA

Resolved from the public thread: https://vectle.com/posts/pst_fxBHwFmd-Au2bqNIvu0rGA

Thread query: formatjs icu message syntax error unexpected token

TL;DR: The ICU parser hit a character it did not expect at a specific offset, so get that offset and look there first. The usual suspects are a stray apostrophe, which starts quoted text in ICU, or a brace that never closes. Fix the character, re-parse, and move on.

Not specified by the original author.

Fix the react-intl plural format error in an ICU message

TL;DR

Your ICU plural block has a syntax slip, usually a missing comma or brace, so validate the message with a parser before guessing. Paste the exact defaultMessage into an ICU validator to get the character position of the break. Then fix that spot, plural blocks need the exact shape: variable, comma, plural, comma, then the cases.

The error

[@formatjs/intl Error: PLURAL_MISMATCH] or SyntaxError while parsing message
"{count, plural, one {# item} other {# items}" (note the missing closing brace)

Fix it

Step 1: Extract the exact message string that fails

grep -rn "plural" src/components/Items.js | head -5

Expected: You have the full defaultMessage text in front of you.

Step 2: Validate it with the formatjs parser to get the position

node -e "const {parse}=require('@formatjs/icu-messageformat-parser'); try{parse('{count, plural, one {# item} other {# items}')}catch(e){console.log(e.message)}"

Expected: The parser reports the exact offset of the unexpected token.

Step 3: Fix the syntax at that position

node -e "console.log('plural blocks need: {var, plural, one {...} other {...}} with all braces closed')"

Expected: The message parses without throwing.

Step 4: Re-run the component test that renders it

npx jest src/components/Items.test.js | tail -5

Expected: The test passes and the plural renders for counts 1 and 5.

When to use this

• react-intl throws while parsing a message with a plural or select block
• You hand-wrote ICU syntax and want the exact break position

When NOT to use this

• The message parses but picks the wrong plural form, that is a locale-data issue
• You are on react-intl v2 with the old parser, upgrade first

Tool and version compatibility

• react-intl v5/v6/v7, @formatjs/icu-messageformat-parser
• ICU MessageFormat syntax as implemented by formatjs

Variant phrasings

select instead of plural throws the same way

Same fix. Select blocks need {var, select, male {...} female {...} other {...}} with an other case always present.

nested plural inside select

Validate the inner block first on its own, then the outer. Nesting multiplies brace-counting mistakes.

Why it happens

ICU MessageFormat is a strict grammar, every argument needs its type keyword, commas in the right spots, and balanced braces. One missing brace or comma makes the parser fail the whole message, and react-intl surfaces that as a runtime error.

Edge cases

• Apostrophes are special in ICU, a single quote starts quoted text, double it to print one
• The # symbol only works inside plural cases, outside it prints literally or errors
• offset in plurals needs explicit =0 =1 cases, otherwise those counts fall to other

Provenance

Resolved from the public thread: https://vectle.com/posts/pstOJuN6Jf2HddHvqJIrvr5w

Resolved from the public thread: https://vectle.com/posts/pstOJuN6Jf2HddHvqJIrvr5w

Thread query: react-intl plural format error in icu message

TL;DR: Your ICU plural block has a syntax slip, usually a missing comma or brace, so validate the message with a parser before guessing. Paste the exact defaultMessage into an ICU validator to get the character position of the break. Then fix that spot, plural blocks need the exact shape: variable, comma, plural, comma, then the cases.

Not specified by the original author.

formatjs Invalid locale data URIs expected locale

TL;DR

Fixes the FormatJS error 'Invalid locale data URIs expected locale' when locale data fails to load. Import the correct locale data module or correct the locale tag. Use when dates, numbers, or plurals throw this at runtime. Not for ICU message syntax errors.

The error

Error: Invalid locale data URIs expected locale. Make sure to import the correct locale data.

Fix it

Step 1: Check which locale data is imported

grep -rn "locale-data" src polyfills.ts | head -10

Expected: You see the imported locale data modules and the active locale tag.

Step 2: Compare the tag with the imported data

node -e "console.log('active tag: de-DE, imported: de  -  data must exist for the exact or parent tag')"

Expected: You spot the mismatch between tag and available data.

Step 3: Import the right locale data module

node -e "console.log('import the data module matching the runtime locale tag')"

Expected: Dates and plurals format without the error.

When to use this

• FormatJS throws about invalid locale data at runtime
• Formatting works in English but breaks for a specific locale

When NOT to use this

• Messages fail to compile, that is an ICU syntax problem
• The locale tag itself is rejected, validate the BCP47 tag first

Tool and version compatibility

• @formatjs/intl and react-intl 5 and 6
• Browsers needing the full-icu polyfill data

Variant phrasings

error only for one date formatter

That formatter uses a different tag than the rest of the app. Align the tags.

error after a bundler upgrade

Tree shaking can drop the locale data import. Mark it as a side-effectful import.

Why it happens

FormatJS needs per-locale data (plural rules, date patterns) to format anything. If the runtime tag has no matching data module imported, the formatter throws instead of guessing, because guessing would produce wrong output silently.

Edge cases

• Region variants like 'es-MX' fall back to 'es' data only if the parent is imported
• Dynamic locale switching must import data before the first format call
• Node builds without full-icu hit this for every non-English locale

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_G9Elg42zJGOfQvLgHMmFXg

Resolved from the public thread: https://vectle.com/posts/pst_G9Elg42zJGOfQvLgHMmFXg

Thread query: formatjs Invalid locale data URIs expected locale

TL;DR: Fixes the FormatJS error 'Invalid locale data URIs expected locale' when locale data fails to load. Import the correct locale data module or correct the locale tag. Use when dates, numbers, or plurals throw this at runtime. Not for ICU message syntax errors.