[RClaudiuM]

MAX_PART_LENGTH is there to stop placeable expansion bombs, but the resolver also applied it to text written directly in a message. Any message with more than 2500 characters of plain text plus a placeable came out as {???}. The same happened when a select expression picked a long variant. As noted in #170, fluent.js and fluent-rs have no such limit.

Changes in fluent.runtime/fluent/runtime/resolver.py:

• Pattern no longer runs the length check on literal elements (text and string literals) or on placeables. Placeables already resolve and check their own value.
• A placeable that wraps a select expression returns the selected variant's string without checking it again. That variant is a pattern from the same message, and its own placeables were already checked when it was resolved.
• The error message now shows the real limit (MAX_PART_LENGTH, 2500). Before, it showed Pattern.MAX_PARTS (1000), which is where the "1000 characters" in the issue title came from.

Message and term references, variables and function results are still checked, so the billion-laughs protection works the same as before. test_bomb.py passes unchanged, and one assertion was added for the corrected limit in the message.

Fixes #170

Before / after

long = xxx…(3000 chars) { $arg }

• Before: {???}, [ValueError('Too many characters in placeable (3001, max allowed is 1000)')]
• After: the full 3004-character string, no errors

Testing

New tests are in fluent.runtime/tests/test_bomb.py, under TestLongText. They cover long text before a placeable (isolating and non-isolating), a long string literal, a long select variant, and a long select variant after text. All 6 of the new and updated tests fail without the fix and pass with it.

uv run pytest fluent.runtime     # 191 passed, 1 skipped
uv run pytest fluent.syntax      # 264 passed, 1 skipped
uv run pytest fluent.pygments    # 3 passed
uv run python -m flake8          # clean
uv run mypy fluent.syntax/fluent fluent.runtime/fluent   # no issues
black --check                    # unchanged