From 73687e8727760388383dfe67aeda0f6461533a47 Mon Sep 17 00:00:00 2001
From: ScottPJones <scottjones@alum.mit.edu>
Date: Thu, 15 Feb 2024 08:35:27 -0500
Subject: [PATCH] Fix issue #83 (from Formatting.jl), handle precision argument
 for Python format string

---
 Project.toml    |  2 +-
 src/fmtcore.jl  | 47 +++++++++++++++++++++++++++++++++--------------
 test/fmtspec.jl | 10 ++++++++++
 3 files changed, 44 insertions(+), 15 deletions(-)

diff --git a/Project.toml b/Project.toml
index 5903583..c177ca6 100644
--- a/Project.toml
+++ b/Project.toml
@@ -23,7 +23,7 @@ keywords = ["Strings", "Formatting"]
 license = "MIT"
 name = "Format"
 uuid = "1fa38f19-a742-5d3f-a2b9-30dd87b9d5f8"
-version = "1.3.3"
+version = "1.3.4"
 
 [deps]
 
diff --git a/src/fmtcore.jl b/src/fmtcore.jl
index c54a641..e02fd7b 100644
--- a/src/fmtcore.jl
+++ b/src/fmtcore.jl
@@ -13,24 +13,43 @@ function _repprint(out::IO, c::AbstractChar, n::Int)
     end
 end
 
-
 ### print string or char
 
+function _truncstr(s::AbstractString, slen, prec)
+    prec == 0 && return ("", 0)
+    i, n = 0, 1
+    siz = ncodeunits(s)
+    while n <= siz
+	(prec -= textwidth(s[n])) < 0 && break
+	i = n
+        n = nextind(s, i)
+    end
+    str = SubString(s, 1, i)
+    return (str, textwidth(str))
+end
+
+_truncstr(s::AbstractChar, slen, prec) = ("", 0)
+
 function _pfmt_s(out::IO, fs::FormatSpec, s::Union{AbstractString,AbstractChar})
-    pad = fs.width - textwidth(s)
-    if pad <= 0
-        print(out, s)
-    elseif fs.align == '<'
-        print(out, s)
-        _repprint(out, fs.fill, pad)
-    elseif fs.align == '^'
-        _repprint(out, fs.fill, pad>>1)
-        print(out, s)
-        _repprint(out, fs.fill, (pad+1)>>1)
-    else
-        _repprint(out, fs.fill, pad)
-        print(out, s)
+    slen = textwidth(s)
+    str, slen = 0 <= fs.prec < slen ? _truncstr(s, slen, fs.prec) : (s, slen)
+    prepad = postpad = 0
+    pad = fs.width - slen
+    if pad > 0
+        if fs.align == '<'
+            postpad = pad
+        elseif fs.align == '^'
+            prepad, postpad = pad>>1, (pad+1)>>1
+        else
+            prepad = pad
+        end
     end
+    # left padding
+    prepad == 0 || _repprint(out, fs.fill, prepad)
+    # print string
+    print(out, str)
+    # right padding
+    postpad == 0 || _repprint(out, fs.fill, postpad)
 end
 
 _unsigned_abs(x::Signed) = unsigned(abs(x))
diff --git a/test/fmtspec.jl b/test/fmtspec.jl
index 90b52a7..b4e98f2 100644
--- a/test/fmtspec.jl
+++ b/test/fmtspec.jl
@@ -54,6 +54,7 @@ end
     @test pyfmt("#b", 6) == "0b110"
     @test pyfmt("#o", 6) == "0o6"
     @test pyfmt("#x", 6) == "0x6"
+    @test pyfmt("#X", 10) == "0XA"
 end
 
 @testset "Format string" begin
@@ -75,6 +76,15 @@ end
     @test pyfmt("⋆^5s", "αβγ") == "⋆αβγ⋆"
     @test pyfmt("*<5s", "abc") == "abc**"
     @test pyfmt("⋆<5s", "αβγ") == "αβγ⋆⋆"
+
+    # Issue #83 (in Formatting.jl)
+    @test pyfmt(".3s", "\U1f595\U1f596") == "🖕"
+    @test pyfmt(".4s", "\U1f595\U1f596") == "🖕🖖"
+    @test pyfmt(".5s", "\U1f595\U1f596") == "🖕🖖"
+
+    @test pyfmt("6.3s", "\U1f595\U1f596") == "🖕    "
+    @test pyfmt("6.4s", "\U1f595\U1f596") == "🖕🖖  "
+    @test pyfmt("6.5s", "\U1f595\U1f596") == "🖕🖖  "
 end
 
 @testset "Format Symbol" begin