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Merged
byroot merged 1 commit into from
Oct 7, 2026
+44 −2
Merged

Preserve float precision in RFC 8785 number formatting #1099

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4 changes: 2 additions & 2 deletions lib/json/ext.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -66,8 +66,8 @@ def shareable_lambda(block) # :nodoc:
if num < 0
num, sign = -num, '-'
end
native_rep = "%.15E" % num
decimal, exponential = native_rep.split('E')
native_rep = num.to_s
decimal, exponential = native_rep.split('e')
exp_val = exponential.to_i
exponential = exp_val > 0 ? ('+' + exp_val.to_s) : exp_val.to_s

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42 changes: 42 additions & 0 deletions test/json/json_generator_test.rb
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Expand Up @@ -1251,6 +1251,48 @@ def test_rfc8785_numbers
assert_rfc8785 '999999999999999700000', 999999999999999700000
assert_rfc8785 '999999999999999900000', 999999999999999900000
assert_rfc8785 '333333333.3333333', 333333333.33333329
assert_rfc8785 '0.30000000000000004', 0.1 + 0.2
end

# https://www.rfc-editor.org/rfc/rfc8785.html#appendix-B
{
'0000000000000000' => '0',
'8000000000000000' => '0',
'0000000000000001' => '5e-324',
'8000000000000001' => '-5e-324',
'7fefffffffffffff' => '1.7976931348623157e+308',
'ffefffffffffffff' => '-1.7976931348623157e+308',
'4340000000000000' => '9007199254740992',
'c340000000000000' => '-9007199254740992',
'4430000000000000' => '295147905179352830000',
'7fffffffffffffff' => nil,
'7ff0000000000000' => nil,
'44b52d02c7e14af5' => '9.999999999999997e+22',
'44b52d02c7e14af6' => '1e+23',
'44b52d02c7e14af7' => '1.0000000000000001e+23',
'444b1ae4d6e2ef4e' => '999999999999999700000',
'444b1ae4d6e2ef4f' => '999999999999999900000',
'444b1ae4d6e2ef50' => '1e+21',
'3eb0c6f7a0b5ed8c' => '9.999999999999997e-7',
'3eb0c6f7a0b5ed8d' => '0.000001',
'41b3de4355555553' => '333333333.3333332',
'41b3de4355555554' => '333333333.33333325',
'41b3de4355555555' => '333333333.3333333',
'41b3de4355555556' => '333333333.3333334',
'41b3de4355555557' => '333333333.33333343',
'becbf647612f3696' => '-0.0000033333333333333333',
'43143ff3c1cb0959' => '1424953923781206.2',
}.each do |bits, expected|
define_method("test_rfc8785_number_#{bits}") do
omit "Float#to_s is not always shortest on this engine" unless RUBY_ENGINE == "ruby"
number = [bits].pack('H*').unpack('G').first
if expected
assert_rfc8785 expected, number
assert_equal number, JSON.parse(JSON.generate(number, rfc8785: true)).to_f
else
assert_raise(JSON::GeneratorError) { JSON.generate(number, rfc8785: true) }
end
end
end

fixtures_path = File.expand_path('../fixtures/rfc8785/', __FILE__)
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