Support for Compilation Time Expressions in Annotations

[graemerocher]

From feature request #8323 this PR implements the following set of features:

1. Declaring literals.

• strings (delimited by single quotes)
• numeric types (int, long, float, double, incl. scientific notation and hex)
• boolean
• null

2. Mathematical operators

• -, /, *, %,^ on numeric types
• + on both numeric types and strings

3. Relational operators

• Standart relational operators (>, <, >=, <=, ==, !=)
• instanceof operator (e.g. 'abc' instanceof T(java.langString))
• matches for regex mathing (e.g. 'abc' matches '^[a-z]*') (including /.+/ syntax for regex)
• empty for checking of an object is null or empty
• Relational operators need to support comparables as well

4. Logical operators

• &&, ||, !. We should probably also allow using aliases here (and, or, not)

5. Working with type references

• as part of instanceof operation
• as an argument for method invocation which is treated as io.micronaut.CutsomType.class (e.g. getBean(T(io.micronaut.CustomType))
• as a type reference followed by static method invocation (e.g. T(java.lang.Math).random())

6. Working with collections

• Accessing by index for lists (e.g. list[1])
• Accessing by key for maps (e.g. map['key'])
• Collection filtering (e.g. ages.filter(age -> age > 18) )
• Collection mapping (e.g. persons.map(p -> p.age) )

For filtering/mapping probably makes sense to support lambda syntax.

7. Accessing object properties

• This should allow chaining property access with . (e.g. object.property.nestedProperty)
• Safe property access allowing to avoid NPE (object?.property.?.nestedProperty)

8. Methods invocation

• Object method invocation (e.g. object.name().lenght())
• Static method invocation (T(java.lang.Math).random())

9. Ternary operator

• Standard expr ? 'trueResult' : 'falseResult'
• Elvis operator (e.g. age?:18, note only makes sense if we implement coercion to boolean for numbers, lists, strings etc.)

10. Object construction

• construction with new keyword (this might be useful in @Value annotation, e.g. @Value(#{ new io.micronaut.CustomType() })
• array construcation (new int[] {1, 2, 3}) - not sure whether this is a useful one, since inlining list gives similar behavior
• lists with {1, 2, 3} syntax
• maps with { 'first': 1, 'second': 2 }

11. Predefined syntax constructs, e.g.

• Getting beans from context (e.g. ctx[io.micronaut.CustomBean])
• Accessing properties (e.g. env['custom.property'] )

See #8323

[graemerocher]

test failures are unrelated and related to the latest changes to the validation module

[sdelamo]

I will review this PR tomorrow.

[sdelamo]

I have created several improvements PRs:

• test: add missing groovy tests #9000
• add missing kotlin test and slightly more idiomatic kotlin code for docs #8999
• imp: use class:isInstance and class:cast #8998
• use ObjectUtils::coerceToBoolean in Utils classes #8997
• test: Test ObjectUtils::coerceToBoolean #8996

It misses package-info.java in the package and subpackages of io.micronaut.expressions.

What’s new section does not contain anything about Expression. It would be great if you could add a link such as:

 `<<evaluatedExpressions, Evaluated Expressions>>`
 

I think this is an exciting feature. I will create an issue in security to support something like: @Secured(condition = "#{authentication.attributes.email == '[email protected]' }

[sonarqubecloud]

SonarCloud Quality Gate failed.   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
77 Code Smells

79.0% Coverage
0.7% Duplication

[graemerocher]

@GavrilovSV I have merged the first cut of this. Thank you for your work implementing the basics of this feature, I think it has great potential.

There are still areas of improvement that I would like to address before GA:

• The performance of bean lookups via the evaluation context. I think we should make context objects effectively singleton and cache them in the evaluation context otherwise I am not sure how well this will perform for hot paths like request processing. Given most of the execution part is marked as @Experimental I am fine to address this later.
• A default context that gives access to the Environment object to simplify writing conditions that resolve properties
• Research into extending the HTTP annotations to allow conditional routes (if we address the performance concern above)
• Probably we should support Comparable interface for logical operators
• Probably we should support collection filtering and mapping. For this I think we should use the lambda syntax alreaded defined in Java and Jakarta EL.

[graemerocher]

@sdelamo

I have created several improvements PRs:

* #9000

* #8999

* #8998

* #8997

* #8996

closed / merged these.

It misses package-info.java in the package and subpackages of io.micronaut.expressions.

This is not public API as it is part of the processor module which is mostly internal API. However we can add this if you feel strongly about it.