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Support OPA v1 'if' rules as single rules #23

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Merged
FallenAngel97 merged 1 commit into from
Jul 6, 2026
Merged

Support OPA v1 'if' rules as single rules #23

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72 changes: 59 additions & 13 deletions grammar.js
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,8 @@ module.exports = grammar({
conflicts: $ => [
[$.membership],
[$.rule_body, $.assignment_operator],
[$.rule_head, $.rule_head_v1],
[$.rule_head],
],

rules: {
Expand Down Expand Up @@ -44,17 +46,38 @@ module.exports = grammar({

// rule = [ "default" ] rule-head { rule-body }
rule: $ =>
seq(
optional($.default),
$.rule_head,
prec.left(repeat1($.rule_body)),
choice(
seq(
optional($.default),
$.rule_head,
prec.left(repeat1($.rule_body)),
),
// OPA v1 comp+if rule: `x := 1 if <body>`. The value lives in the
// head, and the first body is a braced query or a single literal —
// never a v0 `:= term` body — so a following v0 rule whose head
// happens to be named `if` cannot be fused in. Dynamic precedence
// prefers this one-rule parse over "value rule followed by a rule
// named if".
prec.dynamic(1, seq(
optional($.default),
alias($.rule_head_v1, $.rule_head),
prec.left(seq(
alias($.rule_body_v1, $.rule_body),
repeat($.rule_body),
)),
)),
),

// rule-head = var ( rule-head-set | rule-head-obj | rule-head-func | rule-head-comp | "if" )
// rule-head = var ( rule-head-set | rule-head-obj | rule-head-func | "if" )
// The head forms share one dynamic precedence: without prec.right on
// the whole head (which would statically force `var :=` into the v1
// head and break plain constants), GLR needs an explicit preference
// for keeping brackets/args/if in the head over demoting them to body
// literals.
rule_head: $ =>
prec.right(seq(
seq(
$.var,
optional(choice(
optional(prec.dynamic(1, choice(
// rule-head-set = ( "contains" term [ "if" ] ) | ( "[" term "]" )
seq($.contains, $.term, optional($.if)),
// rule-head-obj = "[" term "]" [ rule-head-comp ] [ "if" ]
Expand All @@ -73,11 +96,29 @@ module.exports = grammar({
),
// if
$.if,
)),
)),
))),
),

// OPA v1 rule head with the value bound in the head: `x := 1 if`
rule_head_v1: $ => seq($.var, $.rule_head_comp, $.if),

// The body of a v1 comp+if rule: braced query or single literal.
rule_body_v1: $ =>
choice(
$._braced_query,
$.literal,
),

// rule-head-comp = ( ":=" | "=" ) term
rule_head_comp: $ => seq($.assignment_operator, $.term),
// OPA accepts full expressions as rule values (`f(x) := x + 1 if ...`),
// not just plain terms; expr-every is body-only and stays out. The
// dynamic precedence keeps the value in the head when a rule_body
// value parse would otherwise tie (`q["a"] = 1 { true }`).
rule_head_comp: $ =>
prec.dynamic(1, seq(
$.assignment_operator,
choice($.term, $.expr_infix, $.expr_call, $.expr_parens, $.expr_unary),
)),

// rule-args = term { "," term }
rule_args: $ =>
Expand All @@ -86,7 +127,7 @@ module.exports = grammar({
repeat(seq(',', $.term)),
),

// rule-body = [ "else" [ ( ":=" | "=" ) term ] ] ( "{" query "}" ) | literal
// rule-body = [ "else" [ ( ":=" | "=" ) term ] [ "if" ] ] ( "{" query "}" ) | literal
rule_body: $ =>
seq(
optional(
Expand All @@ -98,15 +139,20 @@ module.exports = grammar({
$.term,
),
),
// OPA v1 else clauses: `else := 2 if { ... }` / `else if { ... }`
optional($.if),
),
),
choice(
seq($.open_curly, $.query, $.close_curly),
$._braced_query,
$.literal,
seq($.assignment, $.term),
// The bound value of a constant rule: `x := 1` or `x = 1`.
seq(choice($.assignment, $.unification), $.term),
),
),

_braced_query: $ => seq($.open_curly, $.query, $.close_curly),

// query = literal { ( ";" | ( [CR] LF ) ) literal }
query: $ =>
seq(
Expand Down
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