fix(nav): a graph rebuild resumes walks in progress instead of snapping them (#60)

tests/nav/controller_v4_test.zig

@@ -115,6 +115,56 @@ test "tick fires onPathInvalidated when the goal dies and no reroute exists" {
     try std.testing.expect(!pf.isNavigating(9));
 }
 
+test "a one-waypoint route walks the rest of a segment and arrives (#60)" {
+    const Pf = PathfinderWith(u64, struct {});
+    var pf = Pf.init(std.testing.allocator, test_config);
+    defer pf.deinit();
+
+    const a = try pf.addNode(.{ .x = 100, .y = 100 }, true);
+    _ = try pf.addNode(.{ .x = 100, .y = 200 }, true);
+
+    var ctx = CallbackCtx.init(std.testing.allocator);
+    defer ctx.deinit();
+    // 40 px short of `a`, as a re-issue finds a walker on its last leg.
+    try ctx.positions.put(7, .{ .x = 100, .y = 140 });
+
+    _ = try pf.navigate(7, a, a, 60.0);
+    var i: usize = 0;
+    while (i < 120 and pf.isNavigating(7)) : (i += 1) {
+        const before = ctx.positions.get(7).?;
+        pf.tick(&ctx, 0.016);
+        // Walks, never jumps: no step beyond the engine's 2 px waypoint
+        // snap (speed·dt is ~1 px here; the jump was the whole 40 px).
+        try std.testing.expect(before.y - ctx.positions.get(7).?.y <= 2.0 + 0.001);
+    }
+
+    try std.testing.expectEqual(@as(usize, 1), ctx.arrived.items.len);
+    try std.testing.expectEqual(a, ctx.arrived.items[0].goal_node);
+    try std.testing.expectEqual(@as(f32, 100), ctx.positions.get(7).?.y);
+}
+
+test "a one-waypoint route is invalidated when its node goes away (#60)" {
+    const Pf = PathfinderWith(u64, struct {});
+    var pf = Pf.init(std.testing.allocator, test_config);
+    defer pf.deinit();
+
+    const a = try pf.addNode(.{ .x = 100, .y = 100 }, true);
+    _ = try pf.addNode(.{ .x = 900, .y = 900 }, false);
+
+    var ctx = CallbackCtx.init(std.testing.allocator);
+    defer ctx.deinit();
+    try ctx.positions.put(9, .{ .x = 100, .y = 140 });
+
+    _ = try pf.navigate(9, a, a, 10.0);
+    pf.tick(&ctx, 0.016);
+    pf.removeNode(a);
+    pf.tick(&ctx, 0.016);
+
+    try std.testing.expectEqual(@as(usize, 0), ctx.arrived.items.len);
+    try std.testing.expectEqual(@as(usize, 1), ctx.invalidated.items.len);
+    try std.testing.expect(!pf.isNavigating(9));
+}
+
 test "plain ctx without settle callbacks still compiles and ticks" {
     const Pf = PathfinderWith(u64, struct {});
     var pf = Pf.init(std.testing.allocator, test_config);

zig-pkg/zig_utils-0.7.3-dUo89yXUAQCzJKSJ4bvzP7jwoTv5ndBCM9PHUM0NkUD5/build.zig

@@ -0,0 +1,48 @@
+const std = @import("std");
+
+pub fn build(b: *std.Build) void {
+    const target = b.standardTargetOptions(.{});
+    const optimize = b.standardOptimizeOption(.{});
+
+    // Static library for linking
+    const lib = b.addLibrary(.{
+        .linkage = .static,
+        .name = "zig_utils",
+        .root_module = b.createModule(.{
+            .root_source_file = b.path("src/root.zig"),
+            .target = target,
+            .optimize = optimize,
+        }),
+    });
+    b.installArtifact(lib);
+
+    // zspec dependency
+    const zspec = b.dependency("zspec", .{
+        .target = target,
+        .optimize = optimize,
+    });
+
+    // zig_utils module for tests
+    const zig_utils_module = b.addModule("zig_utils", .{
+        .root_source_file = b.path("src/root.zig"),
+    });
+
+    // Tests with zspec runner
+    const lib_unit_tests = b.addTest(.{
+        .root_module = b.createModule(.{
+            .root_source_file = b.path("tests/root.zig"),
+            .target = target,
+            .optimize = optimize,
+            .imports = &.{
+                .{ .name = "zspec", .module = zspec.module("zspec") },
+                .{ .name = "zig_utils", .module = zig_utils_module },
+            },
+        }),
+        .test_runner = .{ .path = zspec.path("src/runner.zig"), .mode = .simple },
+    });
+
+    const run_lib_unit_tests = b.addRunArtifact(lib_unit_tests);
+
+    const test_step = b.step("test", "Run unit tests");
+    test_step.dependOn(&run_lib_unit_tests.step);
+}

zig-pkg/zig_utils-0.7.3-dUo89yXUAQCzJKSJ4bvzP7jwoTv5ndBCM9PHUM0NkUD5/build.zig.zon

@@ -0,0 +1,19 @@
+.{
+    .name = .zig_utils,
+    .version = "0.7.3",
+    .fingerprint = 0x6dc482caf73c4a75,
+    .minimum_zig_version = "0.16.0",
+
+    .dependencies = .{
+        .zspec = .{
+            .url = "https://github.com/apotema/zspec/archive/v0.9.2.tar.gz",
+            .hash = "zspec-0.9.1-jaKLbXgMBACFwbNjflhbMyP113leoYjboxn-1UOP-FGw",
+        },
+    },
+
+    .paths = .{
+        "build.zig",
+        "build.zig.zon",
+        "src",
+    },
+}