fix(frontend): reject null payloads in dashboard type predicates

[eugenegujing]

What changes were proposed in this PR?

The five type guards in dashboard/type/type-predicates.ts checked their nested payload with typeof value.<field> === "object", which also accepts null because typeof null === "object" in JavaScript, so an entry like {workflow: null} passed isDashboardWorkflow and the DashboardEntry constructor then crashed with an unrelated TypeError: Cannot read properties of null while dereferencing the payload, instead of reaching its intentional "Unexpected type in DashboardEntry." error path. The guards also returned the falsy input itself rather than false for null/undefined input, violating their declared boolean type-guard signatures.

This PR adds an isNonNullObject type guard (typeof x === "object" && x !== null) to the shared predicate utility (common/util/predicate.ts, next to isDefined) so the correct non-null object check is discoverable and reusable, uses it in the four object-payload guards, and switches all five guards to !!value && ... so they return strict booleans in every path. isDashboardProject's !value.workflow exclusion is deliberately unchanged: a null workflow field means "no workflow data", so an object with a string name still classifies as a project and no valid entry changes classification.

Any related issues, documentation, discussions?

Fixes #6439. The buggy behavior was pinned by the five "(current behavior)" tests added in #6425 (issue #6400), which this PR flips to assert the corrected behavior.

How was this PR tested?

Added predicate.spec.ts (8 tests) covering isNonNullObject and the previously untested isDefined. Updated type-predicates.spec.ts: the four null-payload pins now assert toBe(false), the null/undefined input cases are tightened from toBeFalsy() to toBe(false), and the isDashboardProject null-workflow case keeps asserting true with a comment marking it as an intentional decision; the 5x5 cross-classification matrix and all of its 25 expected values are untouched, confirming that classification of realistic entries is unaffected. Ran locally via yarn ng test --watch=false --include='**/common/util/predicate.spec.ts' --include='**/dashboard/type/type-predicates.spec.ts' (61/61 pass), plus the full frontend suite whose failure set is identical to the unmodified main baseline (pre-existing, environment-related failures only), and tsc --noEmit with zero errors.

Was this PR authored or co-authored using generative AI tooling?

Co-authored using Claude Code(Fable 5).

[github-actions]

Automated Reviewer Suggestions

Based on the git blame history of the changed files, we recommend the following reviewers:

• Contributors with relevant context: @Ma77Ball, @aglinxinyuan, @gracecluvohio
  You can notify them by mentioning @Ma77Ball, @aglinxinyuan, @gracecluvohio in a comment.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.66%. Comparing base (0467c76) to head (51da5ec).

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #6443   +/-   ##
=========================================
  Coverage     74.65%   74.66%           
  Complexity     3438     3438           
=========================================
  Files          1160     1160           
  Lines         45793    45795    +2     
  Branches       5069     5070    +1     
=========================================
+ Hits          34189    34191    +2     
  Misses         9953     9953           
  Partials       1651     1651           

Flag	Coverage Δ		*Carryforward flag
access-control-service	70.00% <ø> (ø)		Carriedforward from 0467c76
agent-service	76.76% <ø> (ø)		Carriedforward from 0467c76
amber	66.81% <ø> (ø)		Carriedforward from 0467c76
computing-unit-managing-service	18.00% <ø> (ø)		Carriedforward from 0467c76
config-service	66.66% <ø> (ø)		Carriedforward from 0467c76
file-service	66.80% <ø> (ø)		Carriedforward from 0467c76
frontend	78.57% <100.00%> (+<0.01%)	⬆️
notebook-migration-service	78.94% <ø> (ø)		Carriedforward from 0467c76
pyamber	91.99% <ø> (ø)		Carriedforward from 0467c76
workflow-compiling-service	55.14% <ø> (ø)		Carriedforward from 0467c76

*This pull request uses carry forward flags. Click here to find out more.

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[eugenegujing]

/request-review @aglinxinyuan

[Copilot]

Pull request overview

This PR fixes a correctness gap in the frontend dashboard entry type guards by ensuring nested “payload” fields are rejected when they are null (avoiding the JavaScript typeof null === "object" trap) and by making the guards return strict booleans for null/undefined inputs. This prevents invalid dashboard entries from being misclassified and crashing DashboardEntry construction with unrelated TypeErrors.

Changes:

• Add a shared isNonNullObject predicate utility and unit tests for it (and for the previously-untested isDefined).
• Update dashboard type predicates to use isNonNullObject for nested object payload checks and !!value to return strict booleans.
• Update dashboard predicate unit tests to assert the corrected null-handling behavior while keeping the cross-classification matrix unchanged.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
frontend/src/app/dashboard/type/type-predicates.ts	Switch nested payload checks to isNonNullObject and ensure strict-boolean returns.
frontend/src/app/dashboard/type/type-predicates.spec.ts	Flip the “current behavior” null-payload pins to assert corrected false results; tighten null/undefined expectations to false.
frontend/src/app/common/util/predicate.ts	Introduce reusable isNonNullObject helper alongside isDefined.
frontend/src/app/common/util/predicate.spec.ts	Add focused unit tests for isNonNullObject and isDefined.

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