fix: TOML parsing of fractional seconds (#59999)

fix a bug in which parsing the digits after the decimal point of a
(date-)time like "00:00:00.12" were interpreted as "12 milliseconds"
instead of "0.12 seconds". Now, the fractional part is correctly parsed
as a fraction of a second, then correctly converted to milliseconds. As
before, only the first three digits after the decimal point are
considered.

Closes #59997

---

With a local build of this PR, the example from the above issue now
evaluates to:
```julia
julia> t2 = TOML.parse("""time = 00:00:00.2""")
Dict{String, Any} with 1 entry:
  "time" => 00:00:00.2

julia> millisecond(t2["time"])
200
```

(cherry picked from commit 906d64e)

Author: haakon-e

base/toml_parser.jl

@@ -1110,7 +1110,7 @@ function _parse_local_time(l::Parser, skip_hour=false)::Err{NTuple{4, Int64}}
     second in 0:59 || return ParserError(ErrParsingDateTime)
 
     # optional fractional second
-    fractional_second = Int64(0)
+    millisecond = Int64(0)
     if accept(l, '.')
         set_marker!(l)
         found_fractional_digit = false
@@ -1121,12 +1121,15 @@ function _parse_local_time(l::Parser, skip_hour=false)::Err{NTuple{4, Int64}}
             return ParserError(ErrParsingDateTime)
         end
         # DateTime in base only manages 3 significant digits in fractional
-        # second
+        # second. Interpret parsed digits as fractional seconds and scale to
+        # milliseconds precision (e.g., ".2" => 200ms, ".20" => 200ms).
+        ndigits = l.prevpos - l.marker
         fractional_second = parse_int(l, false)::Int64
+        millisecond = fractional_second * 10^(3 - ndigits)
         # Truncate off the rest eventual digits
         accept_batch(l, isdigit)
     end
-    return hour, minute, second, fractional_second
+    return hour, minute, second, millisecond
 end
 
 

stdlib/TOML/test/values.jl

@@ -116,6 +116,9 @@ end
     @test testval("2016-09-09T09:09:09Z"    , DateTime(2016 , 9 , 9 , 9 , 9 , 9))
     @test testval("2016-09-09T09:09:09.0Z"  , DateTime(2016 , 9 , 9 , 9 , 9 , 9))
     @test testval("2016-09-09T09:09:09.012" , DateTime(2016 , 9 , 9 , 9 , 9 , 9  , 12))
+    @test testval("2016-09-09T09:09:09.2"   , DateTime(2016 , 9 , 9 , 9 , 9 , 9  , 200))
+    @test testval("2016-09-09T09:09:09.20"  , DateTime(2016 , 9 , 9 , 9 , 9 , 9  , 200))
+    @test testval("2016-09-09T09:09:09.02"  , DateTime(2016 , 9 , 9 , 9 , 9 , 9  , 20))
 
     @test failval("2016-09-09T09:09:09.0+10:00"   , Internals.ErrOffsetDateNotSupported)
     @test failval("2016-09-09T09:09:09.012-02:00" , Internals.ErrOffsetDateNotSupported)
@@ -132,8 +135,12 @@ end
 end
 
 @testset "Time" begin
-    @test testval("09:09:09.99"    , Time(9 , 9 , 9 , 99))
+    @test testval("09:09:09.99"    , Time(9 , 9 , 9 , 990))
     @test testval("09:09:09.99999" , Time(9 , 9 , 9 , 999))
+    @test testval("00:00:00.2"     , Time(0 , 0 , 0 , 200))
+    @test testval("00:00:00.20"    , Time(0 , 0 , 0 , 200))
+    @test testval("00:00:00.23"    , Time(0 , 0 , 0 , 230))
+    @test testval("00:00:00.234"   , Time(0 , 0 , 0 , 234))
 
     @test failval("09:09x09", Internals.ErrParsingDateTime)
 end