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std: in fmt, use tag names of non-exhaustive enums when available #4693

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std: in fmt, use tag names of non-exhaustive enums when available #4693

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038b111
std: allow specifiying enums to be formatted as numbers
daurnimator Mar 10, 2020
c1e60ec
std: in fmt, use tag names of non-exhaustive enums when available
daurnimator Mar 10, 2020
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32 changes: 29 additions & 3 deletions lib/std/fmt.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -359,11 +359,34 @@ pub fn formatType(
},
.Enum => |enumInfo| {
try out_stream.writeAll(@typeName(T));

var has_name: bool = undefined;
if (enumInfo.is_exhaustive) {
has_name = true;
} else {
has_name = false;
// Use @tagName only if value is one of known fields
inline for (enumInfo.fields) |enumField| {
if (@enumToInt(value) == enumField.value) {
has_name = true;
break;
}
}
}

var use_name = has_name;
if (comptime std.mem.eql(u8, fmt, "x") or
comptime std.mem.eql(u8, fmt, "X") or
comptime std.mem.eql(u8, fmt, "d") or
comptime std.mem.eql(u8, fmt, "b"))
{
use_name = false;
}

if (use_name) {
try out_stream.writeAll(".");
try out_stream.writeAll(@tagName(value));
} else {
// TODO: when @tagName works on exhaustive enums print known enum strings
try out_stream.writeAll("(");
try formatType(@enumToInt(value), fmt, options, out_stream, max_depth);
try out_stream.writeAll(")");
Expand Down Expand Up @@ -1293,6 +1316,8 @@ test "enum" {
const value = Enum.Two;
try testFmt("enum: Enum.Two\n", "enum: {}\n", .{value});
try testFmt("enum: Enum.Two\n", "enum: {}\n", .{&value});
try testFmt("enum: Enum(0)\n", "enum: {x}\n", .{Enum.One});
try testFmt("enum: Enum(1)\n", "enum: {X}\n", .{Enum.Two});
}

test "non-exhaustive enum" {
Expand All @@ -1301,11 +1326,12 @@ test "non-exhaustive enum" {
Two = 0xbeef,
_,
};
try testFmt("enum: Enum(15)\n", "enum: {}\n", .{Enum.One});
try testFmt("enum: Enum(48879)\n", "enum: {}\n", .{Enum.Two});
try testFmt("enum: Enum.One\n", "enum: {}\n", .{Enum.One});
try testFmt("enum: Enum.Two\n", "enum: {}\n", .{Enum.Two});
try testFmt("enum: Enum(4660)\n", "enum: {}\n", .{@intToEnum(Enum, 0x1234)});
try testFmt("enum: Enum(f)\n", "enum: {x}\n", .{Enum.One});
try testFmt("enum: Enum(beef)\n", "enum: {x}\n", .{Enum.Two});
try testFmt("enum: Enum(BEEF)\n", "enum: {X}\n", .{Enum.Two});
try testFmt("enum: Enum(1234)\n", "enum: {x}\n", .{@intToEnum(Enum, 0x1234)});
}

Expand Down