Add promql support for the prequel product.

[scunningham]

No description provided.

[Copilot]

Pull Request Overview

This PR adds support for PromQL (Prometheus Query Language) expressions to the prequel compiler, enabling metric-based correlation rules alongside existing log-based rules.

• Introduces NodeTypePromQL schema type and parsing infrastructure for PromQL expressions
• Implements AST building and validation for PromQL nodes with interval and duration support
• Refactors node type checking into reusable helper methods (IsMatcherNode, IsPromNode)

Reviewed Changes

Copilot reviewed 12 out of 13 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
pkg/schema/schema.go	Adds NodeTypePromQL constant, replacing unused NodeTypeDesc
pkg/parser/parse.go	Adds ParsePromQL struct and updates ParseTermT to support PromQL terms
pkg/parser/tree.go	Implements PromQL parsing with nodeFromProm, adds type-checking helpers, refactors node assignment logic
pkg/parser/parse_test.go	Adds test case for PromQL parsing and fixes whitespace formatting
pkg/ast/ast.go	Updates AST builder to handle PromQL nodes and adds PromQL to valid node types
pkg/ast/ast_metrics.go	New file implementing PromQL AST node builder with event and timing support
pkg/ast/ast_machine.go	Adds PromQL case to machine node builder
pkg/ast/ast_log.go	Minor whitespace cleanup
pkg/ast/ast_test.go	Adds PromQL test case and updates line number for test after testdata changes
pkg/testdata/rules.go	Removes unnecessary event sources from error test cases and adds PromQL test data
pkg/datasrc/parse.go	Upgrades yaml dependency from v2 to v3
go.mod / go.sum	Removes yaml.v2 dependency, retaining yaml.v3

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[Copilot]

Inconsistent pattern: buildPromQLNode returns *AstNodeT while buildSeqMatcher and buildSetMatcher return *AstSeqMatcherT and *AstSetMatcherT respectively. Assigning the entire node (promMatcher) to matchNode.Object is incorrect - it should assign promMatcher.Object (which contains the *AstPromQL) to be consistent with the other cases. Alternatively, buildPromQLNode should be refactored to return *AstPromQL directly like the other builder functions.

Suggested change

	matchNode.Object = promMatcher
	matchNode.Object = promMatcher.Object

[scunningham]

Not sure I did this right. @tonymeehan ?

[tonymeehan]

nice