fix: parse CSS rule declarations for RUR metric in figma2code

[Jason59000]

Problem

extract_declarations() in quality.py (line 170-173) filters QualifiedRule.content for Declaration instances, but tinycss2.parse_stylesheet() returns raw component-value tokens (WhitespaceToken, IdentToken, DimensionToken, etc.), not Declaration objects. As a result, CSS declarations inside <style> blocks and external stylesheets contribute zero declarations to the RUR (Relative Unit Share) metric — only inline style="" attributes are counted.

This is consistent with the RUR values in Table 2: all 10 models score between 1.05% and 4.81%, which corresponds to residual inline style usage rather than actual CSS analysis.

Fix

One-line change: call parse_declaration_list() (already imported) on the rule content before filtering for Declaration instances.

Reproduction

import tinycss2
from tinycss2.ast import Declaration

css = 'body { width: 100%; height: 50vh; padding: 1rem; }'
sheet = tinycss2.parse_stylesheet(css)
rule = sheet[0]

# Before fix: 0 declarations found
buggy = [x for x in rule.content if isinstance(x, Declaration)]
print(len(buggy))  # 0

# After fix: 3 declarations found
fixed = tinycss2.parse_declaration_list(rule.content)
print(len([x for x in fixed if isinstance(x, Declaration)]))  # 3

See also: tinycss2 docs — Common Use Cases