Add clap.parsers.enumeration for parsing enums

closes #78

3 files changed, 47 insertions, 0 deletions

diff --git a/README.md b/README.md
index 8457118..d37a222 100644
--- a/README.md
+++ b/README.md
@@ -96,6 +96,7 @@ pub fn main() !void {
     const params = comptime clap.parseParamsComptime(
         \\-h, --help             Display this help and exit.
         \\-n, --number <INT>     An option parameter, which takes a value.
+        \\-a, --answer <ANSWER>  An option parameter which takes an enum.
         \\-s, --string <STR>...  An option parameter which can be specified multiple times.
         \\<FILE>...
         \\
@@ -103,10 +104,12 @@ pub fn main() !void {
 
     // Declare our own parsers which are used to map the argument strings to other
     // types.
+    const YesNo = enum { yes, no };
     const parsers = comptime .{
         .STR = clap.parsers.string,
         .FILE = clap.parsers.string,
         .INT = clap.parsers.int(usize, 10),
+        .ANSWER = clap.parsers.enumeration(YesNo),
     };
 
     var diag = clap.Diagnostic{};
@@ -122,6 +125,8 @@ pub fn main() !void {
         debug.print("--help\n", .{});
     if (res.args.number) |n|
         debug.print("--number = {}\n", .{n});
+    if (res.args.answer) |a|
+        debug.print("--answer = {s}\n", .{@tagName(a)});
     for (res.args.string) |s|
         debug.print("--string = {s}\n", .{s});
     for (res.positionals) |pos|
diff --git a/clap/parsers.zig b/clap/parsers.zig
index 49b95a9..208a1aa 100644
--- a/clap/parsers.zig
+++ b/clap/parsers.zig
@@ -1,6 +1,7 @@
 const std = @import("std");
 
 const fmt = std.fmt;
+const testing = std.testing;
 
 pub const default = .{
     .string = string,
@@ -23,6 +24,10 @@ pub fn string(in: []const u8) error{}![]const u8 {
     return in;
 }
 
+test "string" {
+    try testing.expectEqualStrings("aa", try string("aa"));
+}
+
 pub fn int(comptime T: type, comptime radix: u8) fn ([]const u8) fmt.ParseIntError!T {
     return struct {
         fn parse(in: []const u8) fmt.ParseIntError!T {
@@ -31,6 +36,14 @@ pub fn int(comptime T: type, comptime radix: u8) fn ([]const u8) fmt.ParseIntErr
     }.parse;
 }
 
+test "int" {
+    try testing.expectEqual(@as(u8, 0), try int(u8, 10)("0"));
+    try testing.expectEqual(@as(u8, 1), try int(u8, 10)("1"));
+    try testing.expectEqual(@as(u8, 10), try int(u8, 10)("10"));
+    try testing.expectEqual(@as(u8, 0x10), try int(u8, 0)("0x10"));
+    try testing.expectEqual(@as(u8, 0b10), try int(u8, 0)("0b10"));
+}
+
 pub fn float(comptime T: type) fn ([]const u8) fmt.ParseFloatError!T {
     return struct {
         fn parse(in: []const u8) fmt.ParseFloatError!T {
@@ -39,6 +52,30 @@ pub fn float(comptime T: type) fn ([]const u8) fmt.ParseFloatError!T {
     }.parse;
 }
 
+test "float" {
+    try testing.expectEqual(@as(f32, 0), try float(f32)("0"));
+}
+
+pub const EnumError = error{
+    NameNotPartOfEnum,
+};
+
+pub fn enumeration(comptime T: type) fn ([]const u8) EnumError!T {
+    return struct {
+        fn parse(in: []const u8) EnumError!T {
+            return std.meta.stringToEnum(T, in) orelse error.NameNotPartOfEnum;
+        }
+    }.parse;
+}
+
+test "enumeration" {
+    const E = enum { a, b, c };
+    try testing.expectEqual(E.a, try enumeration(E)("a"));
+    try testing.expectEqual(E.b, try enumeration(E)("b"));
+    try testing.expectEqual(E.c, try enumeration(E)("c"));
+    try testing.expectError(EnumError.NameNotPartOfEnum, enumeration(E)("d"));
+}
+
 fn ReturnType(comptime P: type) type {
     return @typeInfo(P).Fn.return_type.?;
 }
diff --git a/example/simple-ex.zig b/example/simple-ex.zig
index d0d214d..fb20d07 100644
--- a/example/simple-ex.zig
+++ b/example/simple-ex.zig
@@ -11,6 +11,7 @@ pub fn main() !void {
     const params = comptime clap.parseParamsComptime(
         \\-h, --help             Display this help and exit.
         \\-n, --number <INT>     An option parameter, which takes a value.
+        \\-a, --answer <ANSWER>  An option parameter which takes an enum.
         \\-s, --string <STR>...  An option parameter which can be specified multiple times.
         \\<FILE>...
         \\
@@ -18,10 +19,12 @@ pub fn main() !void {
 
     // Declare our own parsers which are used to map the argument strings to other
     // types.
+    const YesNo = enum { yes, no };
     const parsers = comptime .{
         .STR = clap.parsers.string,
         .FILE = clap.parsers.string,
         .INT = clap.parsers.int(usize, 10),
+        .ANSWER = clap.parsers.enumeration(YesNo),
     };
 
     var diag = clap.Diagnostic{};
@@ -37,6 +40,8 @@ pub fn main() !void {
         debug.print("--help\n", .{});
     if (res.args.number) |n|
         debug.print("--number = {}\n", .{n});
+    if (res.args.answer) |a|
+        debug.print("--answer = {s}\n", .{@tagName(a)});
     for (res.args.string) |s|
         debug.print("--string = {s}\n", .{s});
     for (res.positionals) |pos|