Add Path.buildParts helper function

src/path.zig

@@ -54,6 +54,31 @@ pub const Path = struct {
         pub var default = flecs_c;
     };
 
+    /// Creates an array of `EntityPath`s with known size equal to the number of
+    /// elements in the specified tuple argument. Each element of the tuple is
+    /// either converted to a `.name` part, or an `.id` part.
+    ///
+    /// Keep in mind the mutability and lifetime of the string elements passed
+    /// to this function, as they aren't cloned and ownership stays the same.
+    /// In many cases, the lifetime of `Path`s is relatively short. When this
+    /// is not the case, it's recommended to `.clone()` the path after creation.
+    pub fn buildParts(parts: anytype) t: {
+        if (!std.meta.trait.isTuple(@TypeOf(parts)))
+            @compileError("Expected tuple, got '" ++ @typeName(@TypeOf(parts)) ++ "'");
+        const len = @typeInfo(@TypeOf(parts)).Struct.fields.len;
+        break :t [len]EntityPart;
+    } {
+        const len = @typeInfo(@TypeOf(parts)).Struct.fields.len;
+        var result: [len]EntityPart = undefined;
+        inline for (&result, parts) |*res, part|
+            res.* = switch (@TypeOf(part)) {
+                []u8, []const u8 => |name| .{ .name = name },
+                u32, comptime_int => |id| .{ .id = id },
+                else => @compileError("Expected []u8, []const u8, u32 or comptime_int, got '" ++ @typeName(@TypeOf(part)) ++ "'"),
+            };
+        return result;
+    }
+
     /// Creates a new `Path` from the specified string parts.
     ///
     /// The resulting path does not own any of the given slices.
@@ -287,8 +312,22 @@ test Path {
     // Alternatively they can be made by specifying the individual component
     // parts they're made of, as well as an argument specifying whether it's
     // an absolute path.
-    const absolute1 = try Path.fromParts(true, &.{ .{ .name = "I'm" }, .{ .name = "absolute!" } });
-    // No need for `deinit()`, does not own outer array nor inner string parts.
+    // To do this you can use the `buildParts` helper function, which is less
+    // wordy than building `EntityPart` structs manually.
+    const absolute1_parts = Path.buildParts(.{ "I'm", "absolute!" });
+    const absolute1 = try Path.fromParts(true, &absolute1_parts);
+    // No need to call `deinit()`. The path does not own the `absolute1_parts`
+    // array nor the string parts, which in this case are comptime constants.
+
+    // When handling paths, always be aware of the lifetime of its array and
+    // any string parts contained within it. This API allows you to completely
+    // avoid allocation if you know what you are doing.
+    // In the above example, `absolute_parts` is an array allocated onto the
+    // stack, and as such will only be valid until the end of the scope. This
+    // means no allocation is necessary, but it also means `absolute1` is only
+    // valid for as long as its parts.
+    // If a path instance is not immediately consumed and you're uncertain
+    // about the lifetime of its parts, consider using `.clone(alloc)`.
 
     // With `options` unspecified, it's not possible to represent an absolute
     // path using a string. Pass your own `FormatOptions` to be able to.
@@ -309,12 +348,19 @@ test Path {
     try expectEqualStrings("path", relative.parts[2].name);
 
     // Parts can also be numeric ids, used for entities that don't have a name.
-    const numeric = try Path.fromString("100.101.bar", null, alloc);
-    defer numeric.deinit();
-    try expectEqual(@as(usize, 3), numeric.parts.len);
-    try expectEqual(@as(u32, 100), numeric.parts[0].id);
-    try expectEqual(@as(u32, 101), numeric.parts[1].id);
-    try expectEqualStrings("bar", numeric.parts[2].name);
+    const numeric1 = try Path.fromString("100.101.bar", null, alloc);
+    defer numeric1.deinit();
+    try expectEqual(@as(usize, 3), numeric1.parts.len);
+    try expectEqual(@as(u32, 100), numeric1.parts[0].id);
+    try expectEqual(@as(u32, 101), numeric1.parts[1].id);
+    try expectEqualStrings("bar", numeric1.parts[2].name);
+
+    // Numeric ids can also be passed to `buildParts`.
+    const numeric2_parts = Path.buildParts(.{ 100, 101, "bar" });
+    const numeric2 = try Path.fromParts(false, &numeric2_parts);
+
+    // TODO: Let's check numeric1 and numeric2 for equality here.
+    _ = numeric2;
 
     // Paths are formattable. As format specifier you can use options defined
     // on the `FormatOptions` type, or an empty string to use the default.