ArchLang

21. Plan-first: the axonometric view is deprecated ​

  • Status: Accepted
  • Date: 2026-09
  • Scope: compile(src, { view }), the CLI --view flag and src/view/. The height datum (height, sill, head, describe().heights, the Plan JSON height fields) is unchanged.

Context ​

ArchLang draws floor plans. The opt-in axonometric view (view: "iso" | "axon", arch compile --view) was added as a sibling of toScene that extrudes the plan into an illustrative picture. It has never been part of what ArchLang claims:

  • It supports none of the checked claims. ArchLang's argument is that a plan is a checked artifact: reachability, exact areas, byte-identical determinism. The view is, by its own contract, "a picture, never a measured surface" — describe() and lint() never learn it exists, and it carries no scale, no dimensions and no title block. Nothing it draws can be checked against the plan.
  • No consumer. ArchCanvas never imports a view export, and no user has asked for it.
  • It contradicts the positioning. ArchLang is presented as a plan language, not a 3D tool; a picture on the landing page invites a "does it do 3D?" question with no good answer.
  • It carries open bugs (backlog V.1 to V.4) and a maintenance surface across pipeline.ts, the SVG, PDF and DXF backends, the CLI, the compile cache key and ten tests.

The third dimension has a real forward path, and it is data, not drawing: an IFC export of the height datum (backlog P3-2).

Decision ​

  1. ArchLang is plan-first. It draws plans; it does not draw the building.
  2. The view is deprecated in the 1.x line and removed at 2.0, together with the already soft-deprecated while and reassignment. Until then it keeps working and every byte it emits is unchanged.
  3. The deprecation is non-breaking and advisory only. The exports carry @deprecated (toIso, VIEW_NAMES, isViewName, cameraFor, projectedArea2, VIEW_LAYERS, VIEW_LAYER_NAMES, ViewName, Camera, Point3, Projected, CompileOptions.view). The --view flag is described as deprecated in the manifest and, when used, prints one notice on stderr; stdout, --json output and the rendered bytes are untouched. The landing page, sidebar and the agent skill stop promoting it.
  4. The height datum is kept. Heights stay authored, validated (E_HEIGHT_RANGE) and reported by describe(); they still draw nothing on a plan. They become the input of a future data export rather than of a picture.
  5. 3D goes through data export (IFC, backlog P3-2), not through a drawing backend.

Consequences ​

  • Nothing breaks in 1.x. A caller that never passes view sees no change in SVG, describe() or lint().
  • The four open view findings are frozen as won't-fix; they close when the code is deleted.
  • At 2.0 the datum has no drawing consumer until the data export lands. That is accepted: the datum's value is in describe(), which needs no view.
  • A reader who wants a picture of the building has to use a tool that consumes the export.

Phase B: the 2.0 removal checklist ​

Tracked in docs/backlog.md. Prove the removal with a SHA-256 byte-identity sweep of compile, describe and lint over every example before and after.

  • Delete src/view/; the view branch in pipeline.ts; Scene.view; CompileOptions.view.
  • Delete the view branches in backends/svg.ts, export/pdf.ts and export/dxf.ts (the V-3D-* layers).
  • Delete the CLI --view, resolveView and VIEW_FLAG; the index.ts exports; view in the compile cache key.
  • Keep joinWallSet (the plan path uses it); un-export themeBaseLookup if only the view uses it.
  • Delete the ten test/iso-*.test.ts files and the iso snapshot.
  • Delete VIEW_SVGS in scripts/gen-example-svgs.ts, its scripts/check-drift.ts entries and docs-site/public/view/*.svg.
  • Delete docs/axonometric.md, its line in docs-site/sync-docs.mjs and its docs-site/.gitignore entry.
  • The AGENTS.md rule becomes "Heights draw nothing."; drop the view lines in docs/agents/architecture.md; rewrite the backlog note "The datum now has ONE consumer — the axonometric".
  • Note for the sweep: ripgrep treats src/plan-json.ts as binary, so use grep -a there.