Fix bug with precision > length of string

Author: ScottPJones

Project.toml

@@ -23,7 +23,7 @@ keywords = ["Strings", "Formatting"]
 license = "MIT"
 name = "Format"
 uuid = "1fa38f19-a742-5d3f-a2b9-30dd87b9d5f8"
-version = "1.2.1"
+version = "1.2.2"
 
 [deps]
 Printf = "de0858da-6303-5e67-8744-51eddeeeb8d7"

src/printf.jl

@@ -235,7 +235,8 @@ end
 function _fmt(buf, pos, spec::FmtSpec{FmtStr}, arg)
     altf, width, prec = spec.altf, spec.width, spec.prec
     str = altf && (arg isa Symbol || arg isa AbstractString) ? repr(arg) : string(arg)
-    op = p = prec == -1 ? length(str) : prec
+    slen = length(str)
+    op = p = prec == -1 ? slen : min(slen, prec)
     # Make sure there is enough room in buffer
     nlen = max(width, p)
     buflen = sizeof(buf) - pos

test/cformat.jl

@@ -76,6 +76,13 @@ function runtime_float()
         cfmt( "%10.4f", _erfinv( rand() ) )
     end
 end
+function runtime_float_spec()
+    set_seed!( 10 )
+    fs = Format.FmtSpec("%10.4f")
+    for i in 1:200000
+        cfmt( fs, _erfinv( rand() ) )
+    end
+end
 function runtime_float_bypass()
     f = generate_formatter( "%10.4f" )
     set_seed!( 10 )
@@ -87,9 +94,11 @@ end
 println()
 println( "float64 @sprintf speed")
 @time native_float()
-println( "float64 sprintf speed")
+println( "float64 cfmt speed")
 @time runtime_float()
-println( "float64 sprintf speed, bypass repeated lookup")
+println( "float64 cfmt spec speed")
+@time runtime_float_spec()
+println( "float64 cfmt speed, bypass repeated lookup")
 @time runtime_float_bypass()
 
 @testset "test commas..." begin
@@ -103,6 +112,10 @@ println( "float64 sprintf speed, bypass repeated lookup")
     @test cfmt( "%'s", 1234567.0 ) == "1.234567e6"
 end
 
+@testset "Test bug introduced by stdlib/Printf rewrite" begin
+    @test cfmt( "%4.2s", "a" ) == "   a"
+end
+
 @testset "test format..." begin
     @test format( 10 ) == "10"
     @test format( 10.0 ) == "10"
@@ -165,7 +178,9 @@ end
     # same with unspecified width
     @test format(  12345678, commas=true, parens=true )== " 12,345,678 "
     @test format( -12345678, commas=true, parens=true )== "(12,345,678)"
+end
 
+@testset "autoscale" begin
     @test format( 1.2e9, autoscale = :metric ) == "1.2G"
     @test format( 1.2e6, autoscale = :metric ) == "1.2M"
     @test format( 1.2e3, autoscale = :metric ) == "1.2k"
@@ -181,7 +196,9 @@ end
     @test format( 0x100000, autoscale = :binary ) == "1Mi"
     @test format( 0x800, autoscale = :binary ) == "2Ki"
     @test format( 0x400, autoscale = :binary ) == "1Ki"
+end
 
+@testset "suffix" begin
     @test format( 100.00, precision=2, suffix="%" ) == "100.00%"
     @test format( 100, precision=2, suffix="%" ) == "100%"
     @test format( 100, precision=2, suffix="%", conversion="f" ) == "100.00%"