Fix template whitespace collapse merging lines on trailing whitespace#1935
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RobinPicard merged 1 commit intoJul 20, 2026
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The whitespace-collapsing regex in build_template_from_string used \s, which includes newlines. Because the run starts after a word boundary (\b, so the negative lookahead (?![\r\n]) passes), a whitespace run with trailing space before a newline greedily swallowed the line break and the next line's indentation, merging two lines. A single, usually invisible, trailing space after a word would destroy a line break -- e.g. 'foo \nbar' rendered as 'foo bar'. Restrict the collapsed run to horizontal whitespace ([^\S\r\n]) so multi-space runs still collapse to one space while newlines and post-newline indentation are preserved. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01N6RtoHuxrDqTUo9Mw9h4Cv
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📚 Documentation preview: https://dottxt-ai.github.io/outlines/pr-preview/pr-1935/ Preview updates automatically with each commit. |
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What's broken
The whitespace-collapsing regex in
build_template_from_stringuses\s, which includes newlines:The run starts after a word boundary (
\b, so the(?![\r\n])lookahead passes), then\s+greedily eats the following newline and the next line's indentation. So a single, usually invisible, trailing space after a word destroys the line break:An indented multi-line template with one trailing space loses both the newline and the indentation — no user expects a trailing space to merge two lines.
Fix
Restrict the collapsed run to horizontal whitespace (
[^\S\r\n]) so multi-space runs still collapse to one space while newlines and post-newline indentation are preserved. The existing\bguard already preserves post-newline indentation; this stops a collapsed run from crossing a newline.Tests
Adds two cases to
tests/test_templates.py(trailing space preserves the line break; and keeps next-line indentation). Fulltests/test_templates.pypasses (17).