feat: LSP hover with resolved CFN properties and template locations by megha-narayanan · Pull Request #1669 · aws/aws-cdk-cli

megha-narayanan · 2026-06-24T14:39:47Z

Adds LSP hover on construct creation lines showing the resolved CloudFormation logical ID, resource type, construct path, and top-level CFN properties with values
Each property value links to its exact line in the synthesized template; the logical ID header links to the resource block
Multi-resource constructs show auxiliaries inline (≤5 listed individually, >5 collapsed to a type histogram like "6× Subnet, 3× RouteTable")
Extends template-ranges.ts with resolveResourceRanges / indexTemplateRanges to resolve per-property character ranges in a single parse
Exports cfnProperties from the construct tree builder so the hover has access to resolved property values

example hover:

Fixes #

Checklist

This change contains a major version upgrade for a dependency and I confirm all breaking changes are addressed
- Release notes for the new version:

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

…te links Hovering a construct's creation line surfaces its synthesized CloudFormation property values, with each value linking to its location in the template. Adds the cfnProperties attribute to the construct tree, resolveResourceRanges for per-property template ranges, a pure hover content builder, and the onHover server wiring.

Signed-off-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

First-letter-upper only capitalized the first character, so properties whose CloudFormation name has an uppercase acronym run (SSESpecification, EnableECSManagedTags, TemplateURL) did not link and rendered as plain text. The L1 camelCase name and the template PascalCase name differ only in letter case, so key both sides lower-cased. Removes pascalCase.

ShadowCat567

Looks good overall, have some comments about variable names and UI details

ShadowCat567 · 2026-07-02T17:49:19Z

+ * in which case values render without links.
+ */
+export interface HoverLinks {
+  readonly blocks: Record<string, LinkTarget>;


What does blocks refer to in this context? Can it get a more descriptive name?

blocks is the name that was used for the chunk of the template associated with a resource from the template range resolver. Renamed to resourceLocations which better describes what these are, a map from construct path to the location of that resource's definition in the synthesized template. Pushed.

ShadowCat567 · 2026-07-02T18:11:19Z

+}
+
+/** Group auxiliary resources by short CFN type, most common first, e.g. "8× Subnet". */
+function histogram(nodes: readonly ResourceConstruct[]): string {


What does this look like in the hover UI?

realized I needed to include the case where the default is same depth as everything else, so just pushed that bit of code, but it looks like this:

Do you have a test for that? (default same depth as the other constructs)

ShadowCat567 · 2026-07-02T18:16:54Z

+  if (nodes.length === 0) {
+    return undefined;
+  }
+  const value = selection === undefined


Can selection instead be called defaultChild? Since it seems like the logic here revolves around whether the construct we are hovering over has a default child or not

It's not TOTALLY the default child, selectPrimary picks the uniquely shallowest resource on the line, which is usually the default child but could be any uniquely-shallow resource. Renamed to primaryResource, which feels more descriptive than selection without implying the default child relationship specifically. Looks ok?

ShadowCat567 · 2026-07-02T19:33:23Z

+  const properties = primary.cfnProperties ?? {};
+  const keys = Object.keys(properties);
+  const lines = keys.slice(0, MAX_PROPERTIES).map((key) => {
+    const value = `\`${renderValue(properties[key])}\``;


For nested properties like S3Bucket and S3Key in Code for Lambda functions, any particular reason why you render it like:

code: { s3bucket, s3key }

instead of:

code: { s3bucket: <bucket name> s3key: <key zip file> }

mostly just to save hover space, nested CFN values are usually intrinsics or deeply nested objects that make the tooltip very long. Showing key names felt like a good middle ground, and the property value is clickable, so it links to the exact line in the template where the full expansion is visible. happy to expand shallow objects if feels too terse, lmk.

If we have the link to get the information, then this should be fine

…imary selection for VPC - Rename `blocks` → `resourceLocations` for clarity - Rename `selection` → `primaryResource` to avoid confusion with defaultChild - Fix selectPrimary to recognize the default child as primary when peers exist at the same depth (e.g. VPC + IGW + VPCGW all at depth 4)

ShadowCat567 · 2026-07-06T18:00:59Z

+
+/**
+ * Builds the hover for the resource(s) created on a line, given the primary
+ * primaryResource. When one resource is the construct's primary (default) child, its


nit: this comment is confusing if the primary resource is not actually the default child (default child of construct), can you change the wording of this comment and comments like this to describe what you mean by primary child and probably remove the reference to default child if primary child != default child

ShadowCat567 · 2026-07-06T19:18:33Z

+  const properties = primary.cfnProperties ?? {};
+  const keys = Object.keys(properties);
+  const lines = keys.slice(0, MAX_PROPERTIES).map((key) => {
+    const value = `\`${renderValue(properties[key])}\``;


If we have the link to get the information, then this should be fine

…ry vs default-child comments

…#1711) startServer now requires toolkitBindingsFactory (added in #1634/#1669), but the cdk lsp command still called it with only { readable, writable }, breaking the build. Expose startLspServer() from cdk-explorer (wires the Toolkit bindings and starts the server) and call it from the CLI. main.ts becomes that exported function, making cdk lsp the single LSP entrypoint. Fixes # ### Checklist - [ ] This change contains a major version upgrade for a dependency and I confirm all breaking changes are addressed - Release notes for the new version: --- By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

Brings merged LSP work (#1697, #1669, #1670, #1711, #1715) into the explorer branch. CLI command map now carries both 'cdk explore' and 'cdk lsp'; regenerated the user-input files from cli-config.ts. express remains a bundled dependency of the explorer web server.

megha-narayanan temporarily deployed to automation June 24, 2026 14:39 — with GitHub Actions Inactive

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megha-narayanan changed the title ~~feat: LSP hover with resolved CFN properties and template locs~~ feat: LSP hover with resolved CFN properties and template locations Jun 24, 2026

megha-narayanan marked this pull request as ready for review June 24, 2026 16:15

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megha-narayanan requested a review from ShadowCat567 June 24, 2026 16:55

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megha-narayanan and others added 5 commits June 30, 2026 10:45

chore: self mutation

11faac6

Signed-off-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

patch

71275f1

chore: self mutation

d93ee6f

Signed-off-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

megha-narayanan force-pushed the feat/explorer-lsp-hover branch from 6f74962 to 853b11b Compare June 30, 2026 14:45

megha-narayanan had a problem deploying to integ-approval June 30, 2026 14:46 — with GitHub Actions Failure

ShadowCat567 reviewed Jul 2, 2026

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megha-narayanan had a problem deploying to integ-approval July 6, 2026 15:32 — with GitHub Actions Failure

megha-narayanan requested a review from ShadowCat567 July 6, 2026 15:37

ShadowCat567 reviewed Jul 6, 2026

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test(cdk-explorer): cover shallowest-tie default child; clarify prima…

845e25f

…ry vs default-child comments

megha-narayanan had a problem deploying to integ-approval July 6, 2026 20:06 — with GitHub Actions Failure

ShadowCat567 approved these changes Jul 6, 2026

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megha-narayanan merged commit 9aa9168 into aws:feat/cdk-lsp Jul 6, 2026
7 of 8 checks passed

megha-narayanan deleted the feat/explorer-lsp-hover branch July 6, 2026 20:15

megha-narayanan mentioned this pull request Jul 7, 2026

fix(cli): wire 'cdk lsp' through a complete startLspServer entrypoint #1711

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ShadowCat567 Jul 6, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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megha-narayanan commented Jun 24, 2026 •

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ShadowCat567 Jul 6, 2026 •

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