From a84f757ed2ae26fca9fdb8d84d6fffa605b63fae Mon Sep 17 00:00:00 2001
From: "Charlie R.C" <chenr.fnst@cn.fujitsu.com>
Date: Fri, 5 May 2017 00:19:47 -0500
Subject: Allow lookup by shorthand (#106)

---
 flag.go      | 18 ++++++++++++++++++
 flag_test.go |  3 +++
 2 files changed, 21 insertions(+)

diff --git a/flag.go b/flag.go
index f9984fb..6ea0c48 100644
--- a/flag.go
+++ b/flag.go
@@ -319,6 +319,18 @@ func (f *FlagSet) Lookup(name string) *Flag {
 	return f.lookup(f.normalizeFlagName(name))
 }
 
+// ShorthandLookup returns the Flag structure of the short handed flag, returning nil if none exists.
+func (f *FlagSet) ShorthandLookup(name string) *Flag {
+	if name == "" {
+		return nil
+	}
+	if len(name) > 1 {
+		panic("can't look up for a shorthand with name more than one character")
+	}
+	c := name[0]
+	return f.shorthands[c]
+}
+
 // lookup returns the Flag structure of the named flag, returning nil if none exists.
 func (f *FlagSet) lookup(name NormalizedName) *Flag {
 	return f.formal[name]
@@ -399,6 +411,12 @@ func Lookup(name string) *Flag {
 	return CommandLine.Lookup(name)
 }
 
+// ShorthandLookup returns the Flag structure of the short handed flag,
+// returning nil if none exists.
+func ShorthandLookup(name string) *Flag {
+	return CommandLine.ShorthandLookup(name)
+}
+
 // Set sets the value of the named flag.
 func (f *FlagSet) Set(name, value string) error {
 	normalName := f.normalizeFlagName(name)
diff --git a/flag_test.go b/flag_test.go
index 172d49f..8248277 100644
--- a/flag_test.go
+++ b/flag_test.go
@@ -936,6 +936,7 @@ const defaultOutput = `      --A                         for bootstrapping, allo
       --Alongflagname             disable bounds checking
   -C, --CCC                       a boolean defaulting to true (default true)
       --D path                    set relative path for local imports
+  -E, --EEE num[=1234]            a num with NoOptDefVal (default 4321)
       --F number                  a non-zero number (default 2.7)
       --G float                   a float that defaults to zero
       --IP ip                     IP address with no default
@@ -987,6 +988,8 @@ func TestPrintDefaults(t *testing.T) {
 	fs.Lookup("ND1").NoOptDefVal = "bar"
 	fs.Int("ND2", 1234, "a `num` with NoOptDefVal")
 	fs.Lookup("ND2").NoOptDefVal = "4321"
+	fs.IntP("EEE", "E", 4321, "a `num` with NoOptDefVal")
+	fs.ShorthandLookup("E").NoOptDefVal = "1234"
 	fs.StringSlice("StringSlice", []string{}, "string slice with zero default")
 	fs.StringArray("StringArray", []string{}, "string array with zero default")
 
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