Added sum function

[olavsorl]

Description

Adds sum support to the expression engine. The function takes one or multiple lists as argument.

Related Issue(s)

• closes Add sum expression in backend #1789

Verification

• Your code builds clean without any errors or warnings
• Manual testing done (required)
• Relevant automated test added (if you find this hard, leave it and we'll help out)
• All tests run green

Documentation

• User documentation is updated with a separate linked PR in altinn-studio-docs. (if applicable)

Summary by CodeRabbit

Release Notes

• New Features

  • Added a sum expression function to calculate the arithmetic total of numeric values in a list. Supports integers, floating-point numbers, negative values, scientific notation (including numeric strings), and mixed numeric types. Empty lists return 0; all-null lists return 0 (nulls are otherwise ignored).

• Bug Fixes

  • Improved numeric coercion and arithmetic handling for expression calculations.

• Tests

  • Added comprehensive fixture and shared test coverage for success and failure scenarios.

[coderabbitai]

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 13.33% 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
Title check	✅ Passed	The title 'Added sum function' directly and clearly summarizes the main change—adding a sum function to the expression engine.
Linked Issues check	✅ Passed	The PR fully implements all acceptance criteria from issue #1789: adds sum function accepting a list, uses decimal-based algorithm like plus, treats nulls as zero, and returns zero for empty lists.
Out of Scope Changes check	✅ Passed	All changes are directly related to implementing the sum function and its integration into the expression engine as specified in issue #1789.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feature/1789-2-add-sum-expression

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@src/Altinn.App.Core/Internal/Expressions/ExpressionEvaluator.cs`:
- Around line 1040-1050: The validation condition in the Sum method uses AND
(&&) when it should use OR (||), which allows invalid arguments to pass
validation. The condition should ensure that both the argument count is exactly
one AND the argument is an array type. Change the && operator to || in the if
statement so that the exception is correctly thrown when either args.Length is
not equal to 1 OR expressionValue.ValueKind is not JsonValueKind.Array,
preventing non-array values from reaching the .Array property access.

🪄 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: e5b24669-1993-4591-8827-4755164870eb

📥 Commits

Reviewing files that changed from the base of the PR and between 6e40a61 and 183d09e.

📒 Files selected for processing (4)

• src/Altinn.App.Core/Internal/Expressions/ExpressionEvaluator.cs
• src/Altinn.App.Core/Models/Expressions/ExpressionFunction.cs
• test/Altinn.App.Core.Tests/LayoutExpressions/CommonTests/TestFunctions.cs
• test/Altinn.App.Core.Tests/LayoutExpressions/CommonTests/shared-tests/functions/sum/sum.json

[TomasEng]

Har ikke noe særlig å utsette på dette, bare noen spørmål om potensielle forenklinger. Husk å markere sjekkboksene i beskrivelsen. Beskrivelsen sier også "the function takes one or multiple lists as arguments", men den tar vel bare én?

[coderabbitai]

🧹 Nitpick comments (1)

src/Altinn.App.Core/Internal/Expressions/ExpressionEvaluator.cs (1)

1050-1056: 🧹 Nitpick | 🔵 Trivial | 💤 Low value

Consider reordering: validate argument count before accessing element.

The current code calls FirstOrDefault() before validating the argument count. While functionally correct, accessing the element after validation is cleaner and avoids the unnecessary default-value path.

♻️ Suggested reorder

 private static double? Sum(ExpressionValue[] args)
 {
-    var expressionValue = args.FirstOrDefault();
     if (args.Length != 1)
     {
         throw new ExpressionEvaluatorTypeErrorException($"Expected 1 argument(s), got {args.Length}");
     }
+    var expressionValue = args[0];

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@src/Altinn.App.Core/Internal/Expressions/ExpressionEvaluator.cs` around lines
1050 - 1056, In the Sum method, reorder the logic to validate the argument count
before accessing array elements. Move the length validation check (args.Length
!= 1) to occur before the FirstOrDefault() call on the args array. This ensures
that we validate the preconditions first and only then access the
expressionValue, making the code cleaner and avoiding unnecessary default-value
path execution.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@src/Altinn.App.Core/Internal/Expressions/ExpressionEvaluator.cs`:
- Around line 1050-1056: In the Sum method, reorder the logic to validate the
argument count before accessing array elements. Move the length validation check
(args.Length != 1) to occur before the FirstOrDefault() call on the args array.
This ensures that we validate the preconditions first and only then access the
expressionValue, making the code cleaner and avoiding unnecessary default-value
path execution.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 1a583011-c510-47b5-afed-cf698c2a6aaf

📥 Commits

Reviewing files that changed from the base of the PR and between 183d09e and b0a1f28.

📒 Files selected for processing (5)

• src/Altinn.App.Core/Internal/Expressions/ExpressionEvaluator.cs
• src/Altinn.App.Core/Models/Expressions/ExpressionFunction.cs
• test/Altinn.App.Core.Tests/LayoutExpressions/CommonTests/TestFunctions.cs
• test/Altinn.App.Core.Tests/LayoutExpressions/CommonTests/shared-tests/functions/sum/sum.json
• test/Altinn.App.Core.Tests/PublicApiTests.PublicApi_ShouldNotChange_Unintentionally.verified.txt

✅ Files skipped from review due to trivial changes (1)

• test/Altinn.App.Core.Tests/LayoutExpressions/CommonTests/shared-tests/functions/sum/sum.json

🚧 Files skipped from review as they are similar to previous changes (2)

• test/Altinn.App.Core.Tests/LayoutExpressions/CommonTests/TestFunctions.cs
• src/Altinn.App.Core/Models/Expressions/ExpressionFunction.cs

[sonarqubecloud]

Quality Gate passed

Issues
3 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud