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feat: add grid layout algorithm - #8293
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📝 WalkthroughWalkthroughThis change adds a built-in ChangesBuilt-in grid layout
Priority: ➖ Normal Estimated code review effort: 5 (Critical) | ~120 minutes Change: Feature Sequence Diagram(s)sequenceDiagram
participant Parser as Flowchart parser
participant Layout as runGridLayoutCore
participant Router as Grid router
participant Renderer as SVG renderer
Parser->>Layout: LayoutData with node metadata and config.grid
Layout->>Layout: Resolve placements and group geometry
Layout->>Router: Route grid edges
Router-->>Layout: Edge points and route metadata
Layout->>Renderer: Commit node geometry and edge paths
Renderer-->>Renderer: Render SVG paths and labels
Merge Risk: 🔵 Low · up to The worked example may show a different layout than described, and two tests provide incomplete protection against invalid routes. These are bounded gaps that can be fixed or accepted as follow-up before merging. 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
✅ Passed checks (4 passed)
Full details: Docstring CoverageExplanation Docstring coverage is 2.23% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 269 functions across 45 files. (5 skipped: 5 unsupported.) ✨ Finishing Touches 💡 1🧪 Generate unit tests (beta)
🛠️ Fix failing CI checks 💡
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Inline comments:
In
`@packages/mermaid/src/docs/config/schema-docs/config-defs-grid-layout-config.md`:
- Line 17: Update the grid layout configuration reference to document the
supported curve and edgeCornerRadius options with their exact schema and
defaults, matching the grid syntax guide and configuration source; then
regenerate the referenced schema documentation so the generated file includes
both rows.
In `@packages/mermaid/src/rendering-util/layout-algorithms/grid/router.ts`:
- Line 916: Replace the id-prefix checks in buildRoutingContext,
validateSameContainerRoute, and validateContainerSegment with
isEdgeLabelNode(node), importing that helper alongside the existing types.
Preserve the filtering behavior while ensuring user nodes whose IDs start with
“edge-label-” remain routing obstacles.
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il/rendering-elements/edges.spec.jspackages/mermaid/src/rendering-util/rendering-elements/lineJump.tspackages/mermaid/src/rendering-util/types.tspackages/mermaid/src/schemas/config.schema.yamlpackages/mermaid/src/types.ts
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- 🪄 Fix CodeRabbit comments on this PR
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Inline comments:
In `@packages/mermaid/src/docs/community/grid-layout-routing.md`:
- Around line 327-334: Add diagram frontmatter to the worked flowchart that
selects the grid layout, then regenerate the rendered documentation so readers
running the example use the router described below it.
In `@packages/mermaid/src/rendering-util/layout-algorithms/grid/router.ts`:
- Around line 384-408: In the compact-portal assignment block, add a bounded
backward pass after the forward coordinate pass and before calculating
averageAssigned. Clamp the last coordinate to high and each preceding coordinate
to at most the next coordinate minus MIN_PORT_SEPARATION_PX, preserving the
existing span guard and shift logic.
- Around line 1954-1965: Update the direct shortcut alignment check in the
routing function to require exact equality of either connect-point x or y
coordinates instead of using EPS. Keep non-exact points on the topology-routing
path.
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docs/community/grid-layout-routing.mddocs/community/layout-makers-guide.mddocs/syntax/grid-layout.mdpackages/mermaid/src/docs/.vitepress/config.tspackages/mermaid/src/docs/community/grid-layout-routing.mdpackages/mermaid/src/docs/community/layout-makers-guide.mdpackages/mermaid/src/docs/syntax/grid-layout.mdpackages/mermaid/src/rendering-util/layout-algorithms/grid/placement.spec.tspackages/mermaid/src/rendering-util/layout-algorithms/grid/placement.tspackages/mermaid/src/rendering-util/layout-algorithms/grid/router.spec.tspackages/mermaid/src/rendering-util/layout-algorithms/grid/router.tspackages/mermaid/src/rendering-util/layout-algorithms/grid/testMatrix.ddlt.spec.tspackages/mermaid/src/rendering-util/layout-algorithms/grid/types.tspackages/mermaid/src/utils/sanitizeDirective.spec.tspackages/mermaid/src/utils/sanitizeDirective.ts
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- packages/mermaid/src/docs/community/layout-makers-guide.md
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- 🪄 Fix CodeRabbit comments on this PR
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Inline comments:
In `@packages/mermaid/src/rendering-util/layout-algorithms/grid/router.spec.ts`:
- Line 808: In the routing assertions, replace the combined negated four-item
arrayContaining matcher with independent absence checks so each invalid issue
type is verified separately. Apply this change in
packages/mermaid/src/rendering-util/layout-algorithms/grid/router.spec.ts at
lines 808-808 and 858-858.
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I found several concrete correctness and compatibility issues in the new grid layout. I've attached focused repro details and suggested fixes inline.
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Hi @timmy-wright ! I respect the effort you have put in here. Because of it this PR will get 3 initial reviews instead of one due to its size!
[sisyphus-bot]
Review 1 of 3 — Shared code, config & diagram hooks
Note: This is a technical code review only.
Hi @timmy-wright, thank you for this — a grid layout with logical placement and obstacle-aware routing is a big, well-documented piece of work, and the validation notes in the description made it much easier to review. 🙏
Because the PR is ~16.8k lines, we're splitting the review into three focused passes:
- This one: code outside
layout-algorithms/grid/that every Mermaid user runs (edges, line jumps, render registration, layout-utils, config schema, directive sanitization, diagram DB hooks). - Grid algorithm internals.
- Tests & e2e coverage.
What's working well
- 🎉 [praise] The grid-specific endpoint clipping in
rendering-elements/edges.jsis gated behindlayout === 'grid', and the dagre/ELK path is unchanged. CI backs that up: all 8 e2e shards pass and Argos reports no changed baselines on existing snapshots (only an added one). - 🎉 [praise]
terminalMarkerClearanceRectmoved fromvalidateLayout.tsintolayout-utils/helpers.tswithout changing behavior. The old constants andEPStolerance are passed explicitly, and a unit test comes with it. - 🎉 [praise] Config input is handled defensively throughout.
normalizeGridConfig(grid/placement.ts:95-142) checks that every number is finite and non-negative,resolveEdgeCornerRadiusdoes the same, and placements are stored in aMaprather than an object dictionary. The large corner radius is also safe, becausegenerateRoundedPathclamps it to half the segment length. - 🎉 [praise]
placementIdis a neat fix for ER and mindmap. Rendering IDs stay exactly as they were, so there's no DOM or selector churn, and authors can still targetCUSTOMERor their mindmap node IDs. - 🎉 [praise] Flowchart
@{ }metadata now gets the same prototype-key stripping as agentflow before it reachesLayoutData.
Comments & questions
Everything below is a comment or a question; we'd like to hear your thinking.
-
🟡 [important]
sanitizeGridPlacementsdrops legitimate node IDs (utils/sanitizeDirective.ts:37-45)
The key filter useskey.includes('proto') || key.includes('constr'), so placements for nodes such asprotocolGateway,prototypeA,constraintSolver, orconstructorNode(which appears in your own spec) are silently deleted when they come through%%{init}%%or frontmatter. The same substring checks also run on the inner placement keys, where only the allowlist is needed. These keys are user node IDs, not config names. Was the substring match deliberate? If not, could we reject only exact__proto__,constructorandprototypematches, and add a spec case with an ID likeprotocolGateway? -
🟡 [important] Layout-name branching in shared
edges.js(rendering-elements/edges.js:378-487,:737,:805)
CLAUDE.mdasks us not to put layout- or diagram-specific logic in shared rendering code. This adds about 110 lines of grid-only clipping, plus twolayout === 'grid'checks, to the file every diagram uses. Swimlanes already set this precedent. Did you consider keeping the grid logic out ofinsertEdge?- One option is an edge-level capability that the grid layout sets on the edges it owns, such as
edge.portClipping = 'outline-orthogonal'oredge.skipCornerFix.insertEdgewould then branch on what the edge needs, not on which layout produced it. - The clipping helpers could then live in their own module next to the other port utilities.
- That would also make it easy to retrofit swimlanes later.
Would something like that work for grid, or is there a constraint that means it has to live in
insertEdge? - One option is an edge-level capability that the grid layout sets on the edges it owns, such as
-
🟢 [nit] Corner-radius default and validation duplicated in three places
The default of 5 and its validation now appear inresolveEdgeCornerRadius(edges.js:47),roundedCornerRadius(lineJump.ts:74) andGRID_DEFAULTS.edgeCornerRadius. The PR also removes the old "kept in sync" comment fromlineJump.ts. Could one exported helper cover all three, so they can't drift apart? -
🟢 [nit] Explanatory clipping comment removed (
edges.js:~737)
The comment above the endpoint-clipping branch, which explained why swimlanes need their own path, was deleted. Would you be up for a short updated version covering both grid and swimlanes? -
🟢 [nit] Sanitizer branch not scoped to
grid(sanitizeDirective.ts:106)
key === 'placements'matches at any depth, not only undergrid. It's harmless today. Is it worth checking the parent key, so it can't catch an unrelated futureplacementsoption? -
🟢 [nit] Flowchart forwards all node metadata to layouts (
flowchart/flowDb.ts:260,:1091)
The whole@{ }metadata object now reachesLayoutDatafor every flowchart, whatever the layout, but the grid layout only readsrow,column,horizontalAlignandverticalAlign. Is the full object needed downstream? If not, forwarding just those fields would keepLayoutDatalean and stop arbitrary user keys reaching other layout engines.
Separately,stripPrototypeKeysis now copied verbatim inflowDb.tsandagentflowDb.ts. Diagram isolation rules out one importing the other. Would a small shared helper indiagrams/common/make sense? -
💡 [suggestion] Bundle size and the tiny build (
rendering-util/render.ts:83)
The grid code comes to about 100 KB minified; I bundledgrid/on its own to measure it. It's registered outside theinjected.includeLargeFeaturesguard, so it ships in the tiny build and is inlined into the IIFEmermaid.min.js. ESM users only fetch it lazily. Was leaving grid outside that flag (where ELK and cose-bilkent sit) intentional? I'm mentioning it so the size impact is visible. -
💡 [question] Duplicate mindmap node IDs (
mindmap/mindmapDb.ts:266)
Mindmaps allow the same authored ID on more than one node, and all of those nodes get the sameplacementId, so oneconfig.grid.placementsentry would move them all into one cell. Is that intended? A doc note or alog.warnwould help either way.
Security
I traced user input from %%{init}%%, frontmatter, inline @{ row, column } metadata, ER entity names and mindmap node IDs through to the SVG. I found no XSS or injection issues.
-
Nothing in
grid/*.tswrites to the DOM: no.html(),innerHTMLor string-built SVG. Edge labels still go throughcreateText. -
Only numbers reach the path
dattributes, andcurvehas to match an allowed value. -
Placements are stored in a
Map, so there's no prototype-pollution path. -
Very large
roworcolumnvalues don't allocate dense tracks. -
DOMPurify's config and coverage are unchanged. 🎉
-
🟢 [nit / question] The sanitizer checks keys but not value types (
sanitizeDirective.ts:50-58)
row: "x"orrow: { … }gets pastsanitizeGridPlacementsand is only rejected later byvalidateCoordinate, which throws a render error. That's safe, but the sanitizer is looser than the schema (integer ≥ 1, fixed alignment values). Would you want to delete invalid values in the sanitizer, so a bad directive falls back quietly instead of failing the render?
Summary
The shared-code changes are small, careful, and CI shows no visible impact on other layouts. The two points I'd most like your thoughts on are the sanitizer filter, which looks like it drops some real node IDs, and where the grid clipping code should live.
Reviews 2 (algorithm internals) and 3 (tests and e2e) follow as separate comments.
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[sisyphus-bot]
Review 2 of 3: Grid algorithm internals
Note: This is a technical code review only.
This pass covers rendering-util/layout-algorithms/grid/. With about 9k lines of source, it looks at structure rather than going line by line. Like the other two reviews, everything here is a comment or a question. We'd like to understand your intent.
What's working well
- 🎉 [praise] The code fits the repo's layout model cleanly.
index.tspassesprepareGridLayoutandrunGridLayoutCoretocreateCommonLayoutRenderer, and the core works only onLayoutData.- There are no imports from
diagrams/*, and it loads lazily throughrender.ts.
- 🎉 [praise] The resource limits are real, not aspirational. The vertex, adjacency, memory and search-state caps are all named constants. They are checked where the work happens (
routerTopology.ts:689-700,routerSearch.ts:559-565), raise a typedGridRoutingResourceLimitError, and fall back per container. - 🎉 [praise] Layout writes are all-or-nothing. The layout is cloned, run, then committed (
layoutCore.ts:481-487), and bundle and label retries restore a snapshot first, so a failure never leaves half-written coordinates behind. - 🎉 [praise] The code is deterministic and tidy.
- There's no
Math.random,Date,consoleor enums, andimport typeis used throughout. - Forest traversal and absolute positioning use explicit stacks, not recursion, so deep nesting can't overflow the stack.
- Cycles in containment are detected.
- There's no
- 🎉 [praise]
placement.ts,groups.tsandlayoutCore.tsare especially easy to follow.
Comments & questions
-
🟡 [question] The occupancy and crossing costs never seem to be filled in (
routerTopology.ts:732-733,routerSearch.ts:605,:699-700)
The search tuple includesoccupiedLengthandcrossings, but no arc ever getsoccupiedLengthorcrossingCount, so both fall back to?? 0.context.occupancy.routesgets routes pushed to it in five places (router.ts:1749,1900,1935,2821,2909). The only read is at:3091, and that's for snapshot and restore.
As far as I can tell, unrelated edges therefore aren't penalised for sharing a corridor or crossing, even though the description lists both as cost terms. Am I missing where these are filled in, or is this still to be wired up? If it's deferred, removing the unused fields for now (or leaving a TODO) would make the current behavior clearer. -
🟡 [question] Should routing failures throw, or fall back? (
edgeLabels.ts:2345,router.ts:1893,1913,3054,placement.ts:278)
GRID_ROUTE_NOT_FOUND, a vertical-alignment conflict in a shared cell, and an invalid coordinate each abort the whole render. The same happens when the resource-limit fallback route fails its own validation.
edge-routing.mdsays this strictness is deliberate, and it makes sense in tests. But Mermaid runs server-side on GitHub and GitLab, where a less tidy route is usually better than an error diagram. Have you considered a strict mode for tests, with a last-resort unvalidated route pluslog.warnin production? Unknown placement targets already take that softer path. -
🟡 [question] Is the corridor router staying long term? (
router.ts:492,:2548-2601)
routeWithinContaineris both the "compatibility fast path" and the resource fallback, and the sparse visibility router sits beside it. The test hooks (topologyCaps,searchCaps,onDualRouteComparison) also disable the fast path, so tests that use them run a different path from real renders.
Is the plan to keep both routers? It would help to say so inedge-routing.mdeither way. -
🟡 [question] Should one edge's search cost affect routes elsewhere? (
router.ts:1016,routerSearch.ts:466-469)
A singlesearchBudgetof 2M states is shared by every edge in the render. Once it runs out, every later edge falls back to the legacy route. The output stays deterministic, but adding one edge early in the order could quietly worsen routes far away. Did you consider a budget per container or per edge, or at least onelog.warnwhen the shared budget runs out? -
💡 [suggestion] Could
routeGridEdgesbe broken up? (router.ts:2351-3208)
It's about 860 lines, with more than 15 closures over shared mutable maps.restorePairStatecopies 15 metric fields by hand (:3099-3160), so it's easy to miss one when adding a new metric. A small session class or module (plan, fast path, route per plan, bundle retry), plus a generic metrics snapshot, would make this much easier to review and maintain. -
💡 [suggestion] Could
localeComparetie-breaks become a plain comparison? (for examplerouter.ts:2462,routerTopology.ts:424)
localeCompareis used 28 times to break ties, and its ordering can differ by locale and ICU build, so a headless server and a browser could order ties differently. A plain code-unit comparison would rule that out. Swimlanes does the same thing, so this isn't unique to your code. -
🟢 [nit]
EPSmeans two different things. It's1e-6inedgeLabels.ts:21, but theEPSimported fromlayout-utils/geometry.tsis1. Names likeLABEL_EPSandPIXEL_EPSwould make that obvious. -
🟢 [nit] Some helpers and constants duplicate existing ones.
routeLengthrepeatsmanhattanLength(layout-utils/helpers.ts:94).DEFAULT_MAX_ESTIMATED_BYTESis defined in bothrouter.ts:56androuterTopology.ts:24.mergeIntervalsis defined in bothedgeLabels.ts:421androuterTopology.ts:420.- The clamp pattern is written out repeatedly where
helpers.clampalready exists.
-
🟢 [nit] Test-only code ships in the bundle.
findDenseOracleRoute(routerSearch.ts:836) is only used by specs. Could it move into a spec helper? The same goes for a few functions exported only for tests. -
🟢 [nit] Label instrumentation is always on. It is always allocated and incremented in hot paths (
edgeLabels.ts:2029,instrumentation ??= …), even when nothing reads it. Could it stayundefinedunless the caller passes one in? -
🟢 [nit] Placements are validated twice.
runGridLayoutCoreandrunGridLayoutCoreInPlaceeach rebuild the forest and config and each validate placements (layoutCore.ts:438-446,:473-479). Also, the returnedGridLayoutResultpoints at the cloned nodes, not the caller's. -
🟢 [nit] Some types and error codes are inconsistent.
occupancy.routesis typedreadonlybut cast to mutable in six places.router.ts:1829throws a plainErrorwheregridErroris used elsewhere.
-
💡 [question] Are zero-size nodes intentionally rejected? (
layoutCore.ts:49)
isFinitePositiveNumberrejectswidth === 0, so any diagram that emits a zero-size node would throwGRID_MISSING_MEASUREMENT.
Would stacked PRs help here?
This is only a suggestion. If it would be easier on your side, splitting this into three PRs would make each part easier to review on its own:
- Placement, groups and
layoutCore, using the corridor router only. - The sparse visibility router.
- Edge-label placement and rerouting.
Each would have a clearer review scope and test surface.
Thanks again, this is a genuinely impressive piece of engineering. 🚀
There was a problem hiding this comment.
[sisyphus-bot]
Review 3 of 3: Tests & e2e coverage
Note: This is a technical code review only.
This pass covers the unit, DDLT, performance and Playwright tests. Like the other two reviews, it only has comments and questions.
What's working well
- 🎉 [praise] The oracle-based router tests are excellent.
routerSearch.spec.ts:219checks routes against a dense Dijkstra over 10,000 cases, androuterTopology.spec.ts:26checks topology against a brute-force union of the obstacles. That's the right way to gain confidence in a router. - 🎉 [praise] The DDLT setup follows the repo's conventions. Fixtures are parsed from the
.mmdfiles, and stale sizes are caught through a SHA check; everysourceSha256matches its.mmd. Sizes are applied strictly, results go through the unifiedvalidateLayoutsweep, and every fixture has a manifest entry. - 🎉 [praise] The robustness tests are good to have:
- nesting 15,000 levels deep (
groups.spec.ts:58,layoutCore.spec.ts:218) - determinism across 100 runs
- a check that
flowDb.spec.tsstrips__proto__andconstructormetadata keys
- nesting 15,000 levels deep (
- 🎉 [praise] There are no Cypress references and no
.only().
Comments & questions
-
🟡 [question] Can we get visual snapshots for every supported diagram type? (
e2e/rendering/layout/grid-layout.spec.ts)
MostrenderGraphcalls passscreenshot: false(:55,:203,:240,:271,:299). The only screenshots are the three looks at:424, and they all render the same three-node flowchart. The tests at:306and:344callmermaid.renderdirectly.
So Argos currently sees nothing visual for agentflow, class, state, ER, requirement, use case or mindmap, or for groups, loops and labels. Visual regression is the main safeguard for rendering changes in this repo. Could you add a.mmdfixture for each diagram type and each key scenario undere2e/diagrams/grid/?e2e/rendering/mmd-snapshots.spec.tssnapshots those automatically, and the DOM and geometry assertions you already have can stay alongside. -
🟡 [question] Could the 1-second timing test turn flaky in CI? (
grid/performance.spec.ts:267-274)
CI runspnpm test:coverage, and the comment at:267notes that coverage "adds substantial routing overhead". The hardtoBeLessThan(1000)assertion isn't gated, so it could fail on a slow runner.
Would you considerit.skipIf(process.env.CI)or moving it to a bench, while keeping the resource-cap assertions? Also,:283-288shows that this large case takes the fast path for all 500 edges. Is there a large case that actually exercises the search? -
🟡 [question] Can we add tests showing non-grid layouts are unaffected by the shared edge changes? (
rendering-elements/edges.spec.js)
All three newinsertEdgecases uselayout: 'grid'. It would be reassuring to have tests showing that dagre, ELK and swimlane edges:- still get
fixCornerson linear curves - still use radius 5 when
cornerRadiusis unset - never hit grid clipping
A
lineJump.spec.tscase with a customcornerRadius, and a grid case withskipIntersect = true, would round it out. Argos shows no changes today, which is great, but unit tests would protect this going forward. - still get
-
🟡 [question] Are authored placements tested for class, state, requirement and use case? (
grid-layout.spec.ts:112-209)
Those four only run withcolumns: 1auto-placement, while flowchart, ER and mindmap check that placements keyed by authored ID actually move nodes. SinceplacementIdis only added for ER and mindmap, it would be good to confirm that user-written IDs match for the other types too. -
🟡 [question] What does
ddltParity.spec.tsprotect against? (grid/ddltParity.spec.ts:34-54)
The "direct" path repeats the same three calls asrunGridDdlt, so I don't think the test can fail. Was the intent to compare against the browser entry (createCommonLayoutRenderer)? -
🟡 [question] Were these sizes captured in a browser? (
layout-tests/grid/*.sizes.json)
A few look hand-written:- In
routing-group-member, the label "very long HTML label that must detour cleanly" is sized 120×120. simpleandrouting-cell-aware-empty-cellgive every node exactly 180×54.capturedFromdoesn't name a commit.
If they're synthetic, that's fine; labelling them as synthetic would avoid confusion later.
- In
-
🟡 [question] Should a score-0 layout be locked in as the baseline? (
grid/testMatrix.ddlt.spec.ts:292,:401)
routing-group-memberis snapshotted asscore: 0/valid: true. Is that expected for this fixture?
Related:- Route signatures hashed with SHA-256 (
:140) break on any sub-pixel change without saying what moved. - The exact
toBe(10980)inlayout-fixtures.ddlt.spec.ts:75means an improvement also fails CI. The swimlanes sweep usestoBeGreaterThanOrEqualinstead.
Would you consider assertions with a tolerance (bends, crossings, score ≥ baseline)?
- Route signatures hashed with SHA-256 (
-
💡 [suggestion] One test per diagram in the e2e spec (
grid-layout.spec.ts:112-209,:211-284,:410-429)
Several diagram types loop inside onetest(), so the first failure hides the rest.for (const c of cases) test(...)would report each one on its own.
Separately, the direct-render tests at:312-338and:376-396skip the error-diagram check, andassertDiagramNotError(page)would add it. -
💡 [suggestion] Tests that depend on internal counters (
performance.spec.ts,router.spec.ts)
Many assertions check private counters (compatibilityFastPaths,endpointOverlayBuilds,fullEdgeScans, …). That's useful as a complexity guard, but a harmless refactor could break a lot of tests. Maybe keep the counters that express a big-O property and drop the rest? -
🟢 [nit] Edge cases for invalid input (
placement.spec.ts:103-122)
Invalid coordinates are only tested as0andnull. Negative,1.5,NaN, the string"2", and negative or fractionalcolumnswould round this out. So would an empty graph, a single node, and one e2e test showing how a grid error appears to the user. -
🟢 [nit] Small cleanups
placement.spec.ts:79-80creates aconsole.debugspy and restores it straight away.layout-fixtures.ddlt.spec.tsleavesgrid/routing-hierarchy-portalsout of itsarrayContaininglist.helpers.spec.tsonly covers the'end'terminal.- The
sanitizeDirectivespec asserts thatconstructorNodeis dropped. That ties into the ID-filter question in Review 1.
Summary
The algorithm itself is well tested, and the oracle tests are a highlight. The questions above are mostly about the tests that protect downstream users: visual snapshots for each diagram type, and proof that non-grid edges don't change. Looking forward to your thoughts! 🙌
This is a reply to the review 1 of 3 comment by knsv-bot - I'll work through the other two comments soon :) I've truncated the quoted comment as otherwise this one would be HUGE. First, I'm happy to exclude the grid layout from the tiny build, but have not made that change yet. The current implementation leaves grid outside the The existing tiny build is 3,016,240 bytes minified, 819,390 bytes with gzip, and 592,753 bytes with Brotli. Putting grid behind The implemented changes (now pushed) so far address the other review feedback:
Regression coverage was added for the sanitizer boundaries, legitimate placement IDs, parent scoping, metadata filtering, duplicate mindmap IDs, edge capabilities, clipping behavior, corner-radius validation, and grid placement value validation. The focused formatting, lint, and test checks for the latest sanitizer work pass, including all 25 grid placement tests. |
Remainder of quoted comment truncated for readability. Full comment is here: #8293 (review) I'll look at the feasibility of splitting the PR into 3 after lookign at the 3rd review comment. For the other parts of comment 2: Grid routing review responses
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Snipped most of the comment from the quoted reply as otherwise it'd be huge. The full comment is here: #8293 (review) For each of the comments:
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Thanks for the detailed comments @knsv-bot (and @knsv I assume too :). First, thanks for all the encouraging comments! I'll look at the work involved in splitting the PR into 3 PRs. Well, in fairness, I'll get an agent to figure out a strategy for doing that and then decide if it's feasible. As for including this in the minimal mermaid distro, I'll defer to you. It adds about 100k to a 2800k uncompressed bundle. I could go either way TBH. For a couple of the comments in the main grid code (review 2) I decided to add TODOs to the code rather than implement them properly as that would introduce risk in regressions that will be easier to manage as seperate PRs. I'll likely do some of them as follow-up pieces of work. But I'm contemplating including the refactor one with this PR - will decide over the next day or two. |
Stacked PR analysis
The suggestion to split this work into stacked PRs is reasonable. The current PR is large, and smaller review units could make the design, correctness, and test coverage easier to evaluate. The main constraint is that the pieces are not independent: routing consumes geometry produced by the layout core, and edge-label placement can subsequently modify routed edges. Any split should therefore be a dependency-ordered stack in which each PR has a coherent contract and test surface. Original stack suggestionThe original suggestion was:
This decomposition follows the runtime pipeline and broadly matches the existing module boundaries. Its main risk is the first PR's corridor router. That implementation should be a small, intentional baseline rather than substantial temporary code that reviewers must evaluate before the next PR replaces it. The three PRs would also need to be treated as a stack rather than as independent features:
Option 1: Internal engine first, product integration last
Advantages: The algorithm can be reviewed without exposing an incomplete user-facing feature. The final PR is primarily integration and documentation instead of another large algorithm review. Each stage has a clear question: whether geometry, routing, rendered labels, or product integration is correct. Trade-off: Four PRs create more branch and CI management than the original three-PR suggestion. Option 2: Risk-oriented stack
Advantages: Mechanical changes to shared Mermaid infrastructure are separated from the novel grid algorithms. This makes regressions in existing rendering behavior easier to identify and review. Trade-off: It produces more PRs, and the infrastructure changes may appear unmotivated when reviewed without the later stack. Shared abstractions should not be extracted solely to manufacture a first PR. Option 3: Routing-complexity stack
Advantages: Each routing PR establishes a relatively narrow invariant and corresponding test surface. This could be the easiest structure for reviewers who want to evaluate the routing algorithm in depth. Trade-off: Five PRs may be excessive. The routing layers share data structures and invariants, so splitting them too finely could cause reviewers to repeatedly revisit the same code and assumptions. Option 4: Vertical product slices
Advantages: Each PR provides visible user-facing capability and can be demonstrated independently. This can work well when maintainers prefer incremental product delivery over reviewing architectural layers. Trade-off: Beginning with flowchart may cause the engine or public API to inherit flowchart-specific assumptions. Supporting the other diagram types could then require revisiting code already approved in the first PR. It may also temporarily expose grid layout with an incomplete capability set. Option 5: Core feature followed by quality layers
Advantages: The first PR establishes the feature semantics. Later PRs improve route quality, presentation, and resilience without changing the placement model. Trade-off: The conservative router may become temporary production code. Reviewers would need to assess an implementation that is expected to be replaced or substantially changed by the next PR. Deferring resource bounds and recovery could also make the earlier feature PR less safe to merge. RecommendationI recommend Option 1: internal engine first, product integration last, with the third and fourth PRs combined if a four-PR stack is considered too costly. This structure follows the existing module boundaries while avoiding public exposure of a partially implemented layout. It also gives each review a coherent primary question:
If minimizing stack-management overhead is more important, the original three-PR proposal is the next-best option. In that case, the corridor router in the first PR should remain deliberately small, and the PR description should state that it is the baseline routing contract for the following sparse-router PR rather than a separately designed routing system. There is also a practical cost to splitting an already mature PR: reconstructing branch ancestry, redistributing tests and documentation, rerunning CI, and potentially invalidating review already completed against the current diff. Before restructuring, it would be useful to confirm that the expected reduction in review complexity outweighs that disruption. |
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Refactored the grid edge router to separate planning, routing algorithms, constraints, and mutable orchestration without changing its public API or routing behavior. Key changes:
The refactor preserves the existing exported helpers and |
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@knsv @knsv-bot - I've converted this to a stacked PR if that is easier:
I had to get PRs 2, 3, and 4 to target the previous PR in the stack so they are PRs in my fork as I can't create branches in mermaid repo to stack them properly. I did add a whole lot of comments to the code as part of this so have force updated the branch for this PR to contain the full set of commits from all 4 stacked PRs so we know the e2e tests etc pass with the full stack of PRs. If you prefer the stacked PR then let's go that way. Otherwise we can use this PR. Or we can use the stacked PRs to review and then merge this one. I don't mind too much! Edit: apparently github now supports stacked PRs where the PRs cross forks. So I've created an actual stack. 
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Thanks Tim, the stack is a great improvement and makes this much easier to review! Let's go with the stacked PRs and merge them in order. Keeping this PR around as the full-stack integration check is useful too, so we know e2e passes with everything combined. I'll focus on getting this reviewed and merged next week. |
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A stack-split reconstruction commit reintroduced a duplicate copy of two performance.spec.ts tests referencing GridEdgeLabelInstrumentation fields (fullNodeObstacleScans, fullEdgeScans, indexSpanAllocations, maxReroutesPerEdgePerPass) that an earlier commit had already renamed away. This broke pnpm's build:types prepare step for every CI job. Update the duplicate tests to match the current instrumentation field names and drop the now-identical second copy.
…rt cycle routerPlanning.ts imported EDGE_CLEARANCE_PX from routerOccupancy.ts, which closed a cycle with routerConstraint.ts (constraint -> planning -> occupancy -> constraint), failing checkCircle (madge --circular) in CI. Move EDGE_CLEARANCE_PX to routerTopology.ts, a dependency-free module that already hosts the sibling ROUTE_CLEARANCE_PX constant and that routerConstraint.ts already imports from. No behavior change.
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📑 Summary
Adds a built-in
gridlayout for unified Mermaid diagrams. Nodes and groups can be placed with logical rows and columns, while omitted coordinates are filled deterministically. Track sizes come from measured content, multiple items can share a cell, and nested groups are laid out bottom-up.Grid layout is available for flowchart, agentflow, state, class, ER, requirement, use case, and mindmap diagrams. Flowchart and agentflow support inline placement metadata. All supported diagrams can use
config.grid.placements; ER and mindmap accept their authored identifiers instead of requiring generated rendering IDs.State, Architecture, and Block diagrams could use a grid layout - or even just the edge routing algorithm - but I'll leave that for a later PR. Extracting the edge routing algorithm and being able to use it for other diagrams is also something we can do in the future, but not yet.
The change also adds obstacle-aware orthogonal routing, configurable edge curves, shape-aware endpoints, documentation, a development demo, and broad unit, DDLT, performance, and browser coverage.
Stack
This change is being done using this PR stack:
📏 Design Decisions
Placement and configuration
config.grid.placements.Edge routing
Documentation and developer support
📋 Tasks
MERMAID_RELEASE_VERSIONis used for all new features.pnpm changesetand following the prompts. Changesets that add features should beminorand those that fix bugs should bepatch. Please prefix changeset messages withfeat:,fix:, orchore:.Validation