Fix infinite recursion in AutoLayout for empty graphs#25
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…archical algorithm AutoLayoutAlgorithm.ApplyCore's empty-graph (count == 0) fast path unconditionally delegated to the internal HierarchicalLayoutAlgorithm instance. That instance's own registry resolves both 'auto' and 'hierarchical' back to this same AutoLayoutAlgorithm instance (needed so nested 'auto' scopes re-evaluate correctly). Since an empty graph can never contain a container, HierarchicalLayoutAlgorithm.LayoutScope always takes its flat fast path and calls straight back into this same method with the same empty graph whenever the graph or options declare Algorithm as 'auto' or 'hierarchical' - infinite mutual recursion that overflows the stack (confirmed by reproduction: process exit code 0xC00000FD, STATUS_STACK_OVERFLOW). Fix: resolve the cascaded effective algorithm id directly in the empty-graph fast path, and short-circuit straight to the default leaf (layered) whenever it is self-referential, before ever consulting _hierarchical. Every other id still routes through _hierarchical.ApplyCore exactly as before, preserving existing resolution (and resolution-error) behavior unchanged. Added regression tests proving an empty graph with Algorithm explicitly set to 'auto' or 'hierarchical' resolves without crashing.
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This pull request addresses a critical stack overflow issue that occurred when applying the
AutoLayoutAlgorithmto an empty graph with specific algorithm settings. The main changes ensure that self-referential algorithm resolution does not cause infinite recursion, and new tests are added to verify this behavior.Bug fix: Prevent infinite recursion on empty graphs
AutoLayoutAlgorithm.ApplyCoreto detect when the effective algorithm ID is self-referential (either"auto"or"hierarchical") for empty graphs, and to directly delegate to the layered algorithm instead of risking infinite recursion. This prevents a stack overflow when an empty graph explicitly sets its algorithm to"auto"or"hierarchical".Testing: Added regression tests for empty graph algorithm resolution
AutoLayoutAlgorithmTests.cs:Apply_EmptyGraph_ExplicitAutoAlgorithm_ReturnsEmptyTreeensures that an empty graph with algorithm"auto"returns an empty tree without recursion.Apply_EmptyGraph_ExplicitHierarchicalAlgorithm_ReturnsEmptyTreeensures that an empty graph with algorithm"hierarchical"also avoids recursion and returns an empty tree.