PR Lens

PR Lens Skill

PR Lens draws code as visually rich animated diagrams: diffs, architecture, data flows. You describe the diff or codebase as one JSON document (lanes, nodes, edges, ordered flows) and the CLI renders it as animated SVGs. There is no findings lens — PR Lens is a comprehension layer, not a review bot. There is no field for a bug, risk, or security note, and a document that invents one is rejected.

When to Use

• Asked to diagram, visualise, or explain a code change or a system.
• A pull request should carry an architecture or data-flow diagram.
• Keywords: PR Lens, diagram, architecture, data flow, visualise, pull request.

Prerequisites

• Node.js with npx (the CLI runs via npx @coldtea/pr-lens-cli@latest; no install step).
• gh (GitHub CLI) — optional, only for attaching diagrams to PRs.
• Optional canvas publishing calls the third-party service prlens.dev (see step 4b).

How to Run

Run all commands with the terminal tool from the repository root.

1. Read the diff. When representing a code change: git diff --find-renames <base>...<head>. The base is the merge base, not the tip of the base branch. If not expressing a diff, read the code to be visualised.

2. Write the document to .pr-lens/graph.json, following references/graph-document.md. references/example.graph.json is a valid reference with three lanes, all four delta states, a hero edge, a seven-step flow, a nested drill-down tree and a six-step walkthrough. Read it before writing your first document — quicker than reading the reference.

3. Validate, and fix.

   npx @coldtea/pr-lens-cli@latest validate .pr-lens/graph.json

   Fix every failure and run it again. Do not render an invalid document; do not "work around" a failure by deleting the element it names.

4. Render.

   npx @coldtea/pr-lens-cli@latest render .pr-lens/graph.json --theme light

   Render light by default unless the user requests another theme. The SVGs, the manifest and drawn.graph.json land in .pr-lens/, which the CLI adds to the repository's .gitignore. Do not commit any of it — these files are rebuilt from the diff on demand. Each SVG is named after its view, theme and content hash; manifest.json lists them by lens and view.

4b. Canvas push — OPTIONAL, opt-in. Only when the user explicitly asks for a shareable link. This publishes .pr-lens/drawn.graph.json to the third-party service prlens.dev:

npx @coldtea/pr-lens-cli@latest canvas push

It prints three links. Give the user the view link (https://prlens.dev/c/{id}): the full-screen diagram, every view on one page, no login. The edit link (ending in #w=…) lets its holder overwrite the canvas — it is a secret: leave it out of the reply unless asked, never paste it anywhere public. The embed link serves the top view as an SVG for a README. Pushing the same file again updates the same canvas, so "rename that node" is: edit, validate, render, push — the link stays the same. If the push fails, say so and tell the user where the local SVGs are and which is the top view.

5. Attach to a PR, when there is one. Upstream documents gh pr create/edit/comment --attach <path>, but --attach arrived in GitHub CLI 2.99 — check gh --version first (e.g. gh 2.97 does NOT have it). With gh ≥ 2.99: write the body with a Markdown image ![alt](.pr-lens/<view>.svg) (an HTML <img> is left as written and the file appended at the bottom instead; alt text is the one-line caption a reader without images gets), then repeat --attach <path> per referenced diagram:

   gh pr create --title "…" --body-file .pr-lens/body.md --attach .pr-lens/overview-light-<hash>.svg

   Without --attach, use a commit-free path:

   • Upload the SVGs to a gist: gh gist create .pr-lens/<view>.svg, then reference the raw gist URL in the PR body/comment, or
   • Publish via the canvas link (step 4b, with user consent) and link the view URL, or
   • Note the local .pr-lens/ path in the PR body so reviewers can rebuild.

   Once published somewhere durable, let the CLI compose the comment markdown:

   npx @coldtea/pr-lens-cli@latest comment \
     --graph .pr-lens/drawn.graph.json \
     --manifest .pr-lens/manifest.json \
     --asset-base-url <where you published the SVGs>

   --graph takes drawn.graph.json, not the document you wrote — the CLI refuses a document its manifest does not describe. Leave out --asset-base-url and the markdown points at local paths no reader can fetch. The markdown goes to stdout; posting it is your business.

   Attach the views a reviewer needs and leave the rest in .pr-lens/: the top architecture view first, then a data flow if the change has a sequence worth following. Two diagrams usually beat four.

6. Optional automation: npx @coldtea/pr-lens-cli@latest analyze --base <ref> does steps 1–2 by asking a provider (Gemini, OpenAI, or any /chat/completions endpoint) with a key of your own. That is the only path here that needs one; normally you author the document yourself.