fix writeexp and test

Author: bicycle1885

base/ryu/exp.jl

@@ -10,7 +10,7 @@ function writeexp(buf, pos, v::T,
     if x == 0
         buf[pos] = UInt8('0')
         pos += 1
-        if precision > 0
+        if precision > 0 && !trimtrailingzeros
             buf[pos] = decchar
             pos += 1
             for _ = 1:precision

test/ryu.jl

@@ -545,9 +545,9 @@ end # Float16
     end
 
     @testset "Consistency of trimtrailingzeros" begin
-        Ryu.writefixed(0.0, 1, false, false, false, UInt8('.'), true) == "0"
-        Ryu.writefixed(1.0, 1, false, false, false, UInt8('.'), true) == "1"
-        Ryu.writefixed(2.0, 1, false, false, false, UInt8('.'), true) == "2"
+        @test Ryu.writefixed(0.0, 1, false, false, false, UInt8('.'), true) == "0"
+        @test Ryu.writefixed(1.0, 1, false, false, false, UInt8('.'), true) == "1"
+        @test Ryu.writefixed(2.0, 1, false, false, false, UInt8('.'), true) == "2"
     end
 end # fixed
 
@@ -741,6 +741,12 @@ end
     @test Ryu.writeexp(1e+83, 1) == "1.0e+83"
 end
 
+@testset "Consistency of trimtrailingzeros" begin
+    @test Ryu.writeexp(0.0, 1, false, false, false, UInt8('e'), UInt8('.'), true) == "0e+00"
+    @test Ryu.writeexp(1.0, 1, false, false, false, UInt8('e'), UInt8('.'), true) == "1e+00"
+    @test Ryu.writeexp(2.0, 1, false, false, false, UInt8('e'), UInt8('.'), true) == "2e+00"
+end
+
 end # exp
 
 @testset "compact" begin