fix: correct %g format floating-point precision and star width rounding

Motivation:
The %g format operator had two precision-related bugs:
1. Floating-point imprecision in roundedGenericExponent: math.pow(10, -5)
   returns 9.999999999999999E-6 instead of exact 1e-5, causing log10 to
   return -4.3e-17 instead of 0. math.floor(-4.3e-17) incorrectly returns -1.
2. Star width rounding: width.asInt truncates (3.7 → 3) instead of rounding
   (3.7 → 4), not matching go-jsonnet behavior.

Modification:
1. Changed math.floor(math.log10(x)) to math.floor(math.log10(x) + 1e-10)
   in roundedGenericExponent (2 locations). The epsilon (1e-10) corrects
   floating-point errors without breaking values close to powers of 10.
2. Changed width.asInt to Math.round(width.asDouble).toInt for star width
   and star precision (3 locations).
3. Removed debug println statement from formatGeneric.

Result:
- %g and %#g now correctly handle values with negative exponents (0.1, 0.0001)
- Star width/precision arguments now round instead of truncate
- All existing tests pass, plus new comprehensive test coverage
- Matches go-jsonnet and Python % formatting behavior

References:
- Python % formatting documentation
- go-jsonnet v0.21.0 reference implementation

Author: He-Pin

sjsonnet/src/sjsonnet/Format.scala

@@ -1060,10 +1060,10 @@ object Format {
     if (s == 0) 0
     else {
       val abs = math.abs(s)
-      val rawExponent = math.floor(math.log10(abs)).toInt
+      val rawExponent = math.floor(math.log10(abs) + 1e-10).toInt
       val scale = math.pow(10, rawExponent - precision + 1)
       val rounded = Math.round(abs / scale) * scale
-      if (rounded == 0) 0 else math.floor(math.log10(rounded)).toInt
+      if (rounded == 0) 0 else math.floor(math.log10(rounded) + 1e-10).toInt
     }
   }
 

sjsonnet/test/resources/new_test_suite/format_g_precision_fix.jsonnet

@@ -0,0 +1,52 @@
+// Tests for %g and %#g format fixes
+// Verifies floating-point precision fixes in roundedGenericExponent and formatGeneric
+
+// Basic %g tests with various exponents
+std.assertEqual('%g' % 0.1, '0.1') &&
+std.assertEqual('%g' % 0.0001, '0.0001') &&
+std.assertEqual('%g' % 1.0, '1') &&
+std.assertEqual('%g' % 100.0, '100') &&
+std.assertEqual('%g' % 1234567.0, '1.23457e+06') &&
+
+// %#g tests (alternate flag preserves trailing zeros)
+std.assertEqual('%#g' % 0.1, '0.100000') &&
+std.assertEqual('%#g' % 0.0001, '0.000100000') &&
+std.assertEqual('%#g' % 1.0, '1.00000') &&
+std.assertEqual('%#g' % 100.0, '100.000') &&
+std.assertEqual('%#g' % 1234567.0, '1.23457e+06') &&
+
+// Precision-specific tests
+std.assertEqual('%.3g' % 0.0001, '0.0001') &&
+std.assertEqual('%.3g' % 123.456, '123') &&
+std.assertEqual('%.10g' % 0.1, '0.1') &&
+
+// Zero handling
+std.assertEqual('%g' % 0.0, '0') &&
+std.assertEqual('%#g' % 0.0, '0.00000') &&
+
+// Negative values
+std.assertEqual('%g' % -0.1, '-0.1') &&
+std.assertEqual('%#g' % -0.1, '-0.100000') &&
+
+// Very small exponents
+std.assertEqual('%g' % 0.00001, '1e-05') &&
+std.assertEqual('%#g' % 0.00001, '1.00000e-05') &&
+
+// Precision 0 (treated as precision 1)
+std.assertEqual('%.0g' % 0.0, '0') &&
+std.assertEqual('%.0g' % 1.0, '1') &&
+std.assertEqual('%.0g' % 0.1, '0.1') &&
+std.assertEqual('%#.0g' % 1.0, '1.') &&
+
+// Star width rounding (should round, not truncate)
+std.assertEqual('%*g' % [10, 1.0], '         1') &&
+std.assertEqual('%*g' % [10, 0.1], '       0.1') &&
+std.assertEqual('%*g' % [3.7, 1.0], '   1') &&
+
+// Regression tests: values close to powers of 10
+std.assertEqual('%g' % 99.9999, '99.9999') &&
+std.assertEqual('%g' % 9.99999, '9.99999') &&
+std.assertEqual('%g' % 999.999, '999.999') &&
+std.assertEqual('%g' % 0.999999, '0.999999') &&
+
+true

sjsonnet/test/resources/new_test_suite/format_g_precision_fix.jsonnet.golden

@@ -0,0 +1 @@
+true