feat(cel): add fold support

[yashmehrotra]

Summary by CodeRabbit

Release Notes

• New Features

  • Added fold functionality to CEL for processing lists and maps with accumulator patterns.

• Documentation

  • Updated CEL documentation with examples demonstrating fold operations on collections.

• Tests

  • Added test coverage for fold functionality on lists and maps.

[coderabbitai]

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 9e41f878-a1e7-49ba-8366-a5264d5dbf51

📥 Commits

Reviewing files that changed from the base of the PR and between b646c24 and 4612f24.

📒 Files selected for processing (1)

• cel_fold.go

Walkthrough

This PR introduces CEL fold functionality with two independent changes: a new fold library for CEL expressions supporting list and map aggregation patterns, plus documentation examples; and removal of the disabled goconst linter configuration.

Changes

CEL Fold Feature

Layer / File(s)	Summary
API Documentation CEL.md	Added fold examples demonstrating list summation and map value concatenation, with a note that any-typed variables must be wrapped with dyn(...) for CEL comprehension ranges.
Core Fold Implementation cel_fold.go	New file implementing gomplate.fold CEL library with list and map fold macros that rewrite into comprehensions, plus runtime helpers: foldInitialValue (seeding accumulators), sortedMapEntries (stable key ordering), mergeMaps (right-hand overwrite), and zeroValueForFold (type-appropriate neutral values).
Environment Integration cel.go	Appended getFoldCelLibrary() to the CEL environment options in GetCelEnv to activate fold macros and functions.
Tests tests/cel_test.go	Added TestCelFold validating fold over a numeric list, a key/value map, and dynamic objects with JSON output verification.

Linter Configuration Cleanup

Layer / File(s)	Summary
Linter Config .golangci.yml	Removed goconst from the enabled linters list and deleted its dedicated configuration block.

Sequence Diagram

sequenceDiagram
    participant User as User Code
    participant Parser as CEL Parser
    participant Macro as Fold Macro
    participant Comp as CEL Comprehension
    participant Helpers as Runtime Helpers
    participant Result as Result

    User->>Parser: fold(items, acc, expr)
    Parser->>Macro: Invoke fold macro
    Macro->>Macro: Extract identifiers & validate
    Macro->>Helpers: foldInitialValue(items)
    Helpers->>Result: Return seed value
    Macro->>Comp: Generate comprehension<br/>with step expression
    Comp->>Helpers: Call merge() or<br/>accumulator update
    Helpers->>Comp: Return new accumulator
    Comp->>Comp: Iterate over items
    Comp->>Result: Final accumulator value

Loading

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The pull request title 'feat(cel): add fold support' accurately summarizes the main objective of the changeset, which introduces fold support to the CEL environment.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fold-support

✨ Simplify code

• Create PR with simplified code
• Commit simplified code in branch fold-support

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[moshloop]

Suggested change

	{"key": "application", "value": "IIAB"},
	{"key": "application", "value": "ACME"},

[coderabbitai]

Actionable comments posted: 3

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@cel_fold.go`:
- Around line 109-112: The temporary fold entry name generation (entryVar) in
cel_fold.go currently only tries a single fallback "__fold_entry2__" and can
still collide with user vars; change the logic that sets entryVar so it
iteratively picks a name that does not conflict with keyVar, valVar, or accuVar
(e.g., "__fold_entry__", "__fold_entry2__", "__fold_entry3__", ...) by
looping/incrementing a suffix until an unused name is found; update any code
that references entryVar to use the chosen unique name.
- Around line 152-157: The code currently picks the fold seed by using
m.Iterator() and taking the first iteration result (it.HasNext()/it.Next()),
which is nondeterministic for Go maps; change foldInitialValue logic to select
the seed deterministically by enumerating map keys (use m.Keys() or collect
entries), convert keys to a stable sortable representation (e.g., string form),
sort them, pick the first sorted key, and then call m.Get(firstKey) to set
first; keep the same conversion to types.DefaultTypeAdapter.NativeToValue(nil)
where needed and update any references to first and foldInitialValue
accordingly.
- Around line 180-182: The comparator used in sort.SliceStable(keys, ...) is not
a total order because it only compares fmt.Sprint(keys[i].Value()) —
different-typed values like int(1) and string("1") stringify the same and can
leave the order undefined; update the comparator for the keys slice (the
sort.SliceStable call) to produce a total ordering by incorporating the value
type before the stringified value (for example using the value's concrete type
name or a type-tag plus the printed value via reflect.TypeOf or
fmt.Sprintf("%T:%v")) so that items with equal printed forms but different types
are ordered deterministically.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: cdc9cc48-a9d3-40e9-87e5-07bce712f179

📥 Commits

Reviewing files that changed from the base of the PR and between cac6eb1 and b646c24.

📒 Files selected for processing (5)

• .golangci.yml
• CEL.md
• cel.go
• cel_fold.go
• tests/cel_test.go

💤 Files with no reviewable changes (1)

• .golangci.yml