Add canvas-specific intake validation for external plugins

.github/ISSUE_TEMPLATE/external-plugin.yml

@@ -15,6 +15,8 @@ body:
         - Public submissions are **GitHub-only** in v1.
         - The plugin must live in a **public GitHub repository**.
         - Provide an immutable **ref**, **sha**, or both for review.
+        - If your plugin includes a canvas extension, include the **canvas** keyword.
+        - Canvas plugins are validated for `logo: "assets/preview.png"` using the submitted immutable **sha** or **ref**.
         - Do **not** open a PR that edits `plugins/external.json` directly.
   - type: input
     id: plugin-name
@@ -106,7 +108,7 @@ body:
     id: keywords
     attributes:
       label: Keywords
-      description: Comma-separated or newline-separated lowercase tags.
+      description: Comma-separated or newline-separated lowercase tags. Include `canvas` if the plugin contains a canvas extension.
       placeholder: |
         automation
         github

.github/workflows/external-plugin-command-router.yml

@@ -559,7 +559,11 @@ jobs:
               owner: context.repo.owner,
               repo: context.repo.repo,
               issueNumber: context.issue.number,
-              desiredLabels: new Set(['external-plugin', 'ready-for-review'])
+              desiredLabels: new Set([
+                'external-plugin',
+                'ready-for-review',
+                ...(labelNames.has('external-plugin-canvas') ? ['external-plugin-canvas'] : [])
+              ])
             });
 
             const marker = '<!-- external-plugin-mark-ready-override -->';

.github/workflows/setup-labels.yml

@@ -44,6 +44,10 @@ jobs:
                 color: 'FEF2C0',
                 description: 'Public external plugin submission'
               },
+              'external-plugin-canvas': {
+                color: '1D76DB',
+                description: 'External plugin submission includes a canvas extension'
+              },
               'hooks': {
                 color: 'C2E0C6',
                 description: 'PR touches hooks'

eng/external-plugin-intake-state.mjs

@@ -3,6 +3,10 @@ export const EXTERNAL_PLUGIN_INTAKE_LABELS = Object.freeze({
     color: "FEF2C0",
     description: "Public external plugin submission",
   },
+  "external-plugin-canvas": {
+    color: "1D76DB",
+    description: "External plugin submission includes a canvas extension",
+  },
   "awaiting-review": {
     color: "FBCA04",
     description: "Submission is waiting for automated intake validation",
@@ -27,6 +31,7 @@ export const EXTERNAL_PLUGIN_INTAKE_LABELS = Object.freeze({
 
 const EXTERNAL_PLUGIN_INTAKE_SYNC_LABELS = Object.freeze([
   "external-plugin",
+  "external-plugin-canvas",
   "awaiting-review",
   "ready-for-review",
   "requires-submitter-fixes",
@@ -129,6 +134,9 @@ export async function applyExternalPluginIntakeEvaluation({
     rejected: new Set(["external-plugin", "rejected"]),
   };
   const desiredLabels = desiredLabelsByState[state] ?? desiredLabelsByState.rejected;
+  if (evaluation.isCanvasPlugin) {
+    desiredLabels.add("external-plugin-canvas");
+  }
 
   await syncExternalPluginIntakeLabels({
     github,

eng/external-plugin-intake.mjs

@@ -54,6 +54,13 @@ const FIELD_TITLES = Object.freeze({
 const LEGACY_FIELD_TITLES = Object.freeze({
   immutableRef: "Immutable ref to review",
 });
+const EXTERNAL_CANVAS_KEYWORD = "canvas";
+const EXTERNAL_CANVAS_PREVIEW_PATH = "assets/preview.png";
+const EXTERNAL_PLUGIN_ROOT_MANIFEST_PATHS = Object.freeze([
+  ".github/plugin/plugin.json",
+  ".plugin/plugin.json",
+  "plugin.json",
+]);
 
 function normalizeMultilineText(value) {
   return String(value ?? "").replace(/\r\n/g, "\n");
@@ -116,6 +123,29 @@ function parseKeywords(value) {
   return keywords.length > 0 ? keywords : undefined;
 }
 
+function hasCanvasKeyword(plugin) {
+  return (plugin?.keywords ?? []).some(
+    (keyword) => String(keyword).trim().toLowerCase() === EXTERNAL_CANVAS_KEYWORD,
+  );
+}
+
+function normalizeRepoRelativePath(value) {
+  const normalized = stripNoResponse(value);
+  if (!normalized || normalized === "/") {
+    return "";
+  }
+
+  return normalized.replace(/\\/g, "/").replace(/^\/+|\/+$/g, "");
+}
+
+function joinRepoPath(...segments) {
+  return segments
+    .map((segment) => String(segment ?? "").trim())
+    .filter(Boolean)
+    .join("/")
+    .replace(/\/+/g, "/");
+}
+
 function parseChecklist(value) {
   const checked = new Set();
   const normalized = normalizeMultilineText(value);
@@ -231,6 +261,33 @@ async function fetchGitHubJson(apiPath, token) {
   }
 }
 
+function encodeRepoContentPath(value) {
+  return String(value)
+    .split("/")
+    .filter((segment) => segment.length > 0)
+    .map((segment) => encodeURIComponent(segment))
+    .join("/");
+}
+
+async function fetchGitHubFile(repo, filePath, ref, token) {
+  const encodedRepo = encodeRepoPath(repo);
+  const encodedPath = encodeRepoContentPath(filePath);
+  return fetchGitHubJson(
+    `/repos/${encodedRepo}/contents/${encodedPath}?ref=${encodeURIComponent(ref)}`,
+    token,
+  );
+}
+
+function decodeGitHubFileContent(fileResponse) {
+  const encodedContent = fileResponse?.data?.content;
+  if (!encodedContent || typeof encodedContent !== "string") {
+    return null;
+  }
+
+  const normalized = encodedContent.replace(/\n/g, "");
+  return Buffer.from(normalized, "base64").toString("utf8");
+}
+
 function encodeRepoPath(repo) {
   const [owner, name] = String(repo).split("/");
   return `${encodeURIComponent(owner ?? "")}/${encodeURIComponent(name ?? "")}`;
@@ -273,6 +330,7 @@ async function validateRemoteRepository(repo, { ref, sha }, errors, warnings, to
         );
       }
     }
+
   }
 
   if (!ref) {
@@ -322,6 +380,102 @@ async function validateRemoteRepository(repo, { ref, sha }, errors, warnings, to
   }
 }
 
+async function validateCanvasPluginMetadata(plugin, errors, warnings, token) {
+  const repo = plugin?.source?.repo;
+  const sha = plugin?.source?.sha;
+  const ref = plugin?.source?.ref;
+  const releaseLocator = sha || ref;
+  const releaseLocatorDescription = sha ? `commit "${sha}"` : `ref "${ref}"`;
+  const pluginRoot = normalizeRepoRelativePath(plugin?.source?.path);
+
+  if (!releaseLocator) {
+    errors.push('submission: plugins tagged with "canvas" must provide "Ref to review" and/or "Commit SHA to review"');
+    return;
+  }
+
+  if (!repo) {
+    return;
+  }
+
+  let manifest = null;
+  let manifestPath = null;
+  let sawManifestApiError = false;
+
+  const manifestCandidates = EXTERNAL_PLUGIN_ROOT_MANIFEST_PATHS.map((relativePath) =>
+    joinRepoPath(pluginRoot, relativePath),
+  );
+
+  for (const candidatePath of manifestCandidates) {
+    const response = await fetchGitHubFile(repo, candidatePath, releaseLocator, token);
+    if (response.kind === "notFound") {
+      continue;
+    }
+
+    if (response.kind === "apiError") {
+      sawManifestApiError = true;
+      continue;
+    }
+
+    if (response.data?.type !== "file") {
+      continue;
+    }
+
+    const decoded = decodeGitHubFileContent(response);
+    if (!decoded) {
+      errors.push(`submission: could not decode plugin manifest "${candidatePath}" at ${releaseLocatorDescription}`);
+      return;
+    }
+
+    try {
+      manifest = JSON.parse(decoded);
+      manifestPath = candidatePath;
+      break;
+    } catch (error) {
+      errors.push(
+        `submission: plugin manifest "${candidatePath}" at ${releaseLocatorDescription} is not valid JSON (${error.message})`,
+      );
+      return;
+    }
+  }
+
+  if (!manifest) {
+    if (sawManifestApiError) {
+      warnings.push(
+        `submission: could not verify canvas plugin manifest in GitHub repository "${repo}" at ${releaseLocatorDescription}; a maintainer should re-run intake`,
+      );
+      return;
+    }
+
+    const expectedPaths = manifestCandidates.map((candidatePath) => `"${candidatePath}"`).join(", ");
+    errors.push(
+      `submission: plugins tagged with "canvas" must include a manifest at one of ${expectedPaths} in ${releaseLocatorDescription}`,
+    );
+    return;
+  }
+
+  if (manifest.logo !== EXTERNAL_CANVAS_PREVIEW_PATH) {
+    errors.push(
+      `submission: plugins tagged with "canvas" must set "logo" to "${EXTERNAL_CANVAS_PREVIEW_PATH}" in "${manifestPath}"`,
+    );
+  }
+
+  const previewPath = joinRepoPath(pluginRoot, EXTERNAL_CANVAS_PREVIEW_PATH);
+  const previewResponse = await fetchGitHubFile(repo, previewPath, releaseLocator, token);
+  if (previewResponse.kind === "notFound") {
+    errors.push(
+      `submission: plugins tagged with "canvas" must include "${EXTERNAL_CANVAS_PREVIEW_PATH}" at ${releaseLocatorDescription}`,
+    );
+  } else if (previewResponse.kind === "apiError") {
+    warnings.push(
+      `submission: could not verify "${EXTERNAL_CANVAS_PREVIEW_PATH}" in GitHub repository "${repo}" at ${releaseLocatorDescription}; a maintainer should re-run intake`,
+    );
+  } else if (previewResponse.data?.type !== "file") {
+    errors.push(
+      `submission: "${EXTERNAL_CANVAS_PREVIEW_PATH}" must be a file in ${releaseLocatorDescription}`,
+    );
+  }
+}
+
 export function parseExternalPluginIssueBody(body) {
   const sections = parseIssueFormSections(body);
   const errors = [];
@@ -606,6 +760,7 @@ export async function evaluateExternalPluginIssue({ issue, token, runId, owner,
   const validationResult = validateExternalPlugin(parsed.plugin, 0, { policy: "publicSubmission" });
   errors.push(...validationResult.errors.map(toSubmissionError));
   warnings.push(...validationResult.warnings.map(toSubmissionError));
+  const isCanvasPlugin = hasCanvasKeyword(parsed.plugin);
 
   if (parsed.plugin?.name) {
     const matchingName = duplicateNames.find(
@@ -620,6 +775,10 @@ export async function evaluateExternalPluginIssue({ issue, token, runId, owner,
     await validateRemoteRepository(parsed.plugin.source.repo, parsed.plugin.source, errors, warnings, token);
   }
 
+  if (isCanvasPlugin) {
+    await validateCanvasPluginMetadata(parsed.plugin, errors, warnings, token);
+  }
+
   const dedupedErrors = [...new Set(errors)];
   const dedupedWarnings = [...new Set(warnings)];
   const valid = dedupedErrors.length === 0;
@@ -687,6 +846,7 @@ export async function evaluateExternalPluginIssue({ issue, token, runId, owner,
     errors: dedupedErrors,
     warnings: dedupedWarnings,
     plugin: parsed.plugin,
+    isCanvasPlugin,
     commentBody,
     commentMarker: marker,
   };