git.delta.rocks / jrsonnet / refs/commits / 0f5ef44c0f70

difftreelog

feat experimental null-coaelse operator

Yaroslav Bolyukin2023-07-26parent: #3302e38.patch.diff
in: master

6 files changed

modifiedcrates/jrsonnet-evaluator/Cargo.tomldiffbeforeafterboth
--- a/crates/jrsonnet-evaluator/Cargo.toml
+++ b/crates/jrsonnet-evaluator/Cargo.toml
@@ -24,6 +24,8 @@
 exp-object-iteration = []
 # Bigint type
 exp-bigint = ["num-bigint", "jrsonnet-types/exp-bigint"]
+# obj?.field, obj?.['field']
+exp-null-coaelse = ["jrsonnet-parser/exp-null-coaelse"]
 
 # Improves performance, and implements some useful things using nightly-only features
 nightly = ["hashbrown/nightly"]
modifiedcrates/jrsonnet-evaluator/src/evaluate/mod.rsdiffbeforeafterboth
before · crates/jrsonnet-evaluator/src/evaluate/mod.rs
1use std::rc::Rc;23use jrsonnet_gcmodule::{Cc, Trace};4use jrsonnet_interner::IStr;5use jrsonnet_parser::{6	ArgsDesc, AssertStmt, BindSpec, CompSpec, Expr, FieldMember, FieldName, ForSpecData,7	IfSpecData, LiteralType, LocExpr, Member, ObjBody, ParamsDesc,8};9use jrsonnet_types::ValType;1011use self::destructure::destruct;12use crate::{13	arr::ArrValue,14	destructure::evaluate_dest,15	error::{suggest_object_fields, ErrorKind::*},16	evaluate::operator::{evaluate_add_op, evaluate_binary_op_special, evaluate_unary_op},17	function::{CallLocation, FuncDesc, FuncVal},18	throw,19	typed::Typed,20	val::{CachedUnbound, IndexableVal, StrValue, Thunk, ThunkValue},21	Context, GcHashMap, ObjValue, ObjValueBuilder, ObjectAssertion, Pending, Result, State,22	Unbound, Val,23};24pub mod destructure;25pub mod operator;2627pub fn evaluate_trivial(expr: &LocExpr) -> Option<Val> {28	fn is_trivial(expr: &LocExpr) -> bool {29		match &*expr.0 {30			Expr::Str(_)31			| Expr::Num(_)32			| Expr::Literal(LiteralType::False | LiteralType::True | LiteralType::Null) => true,33			Expr::Arr(a) => a.iter().all(is_trivial),34			Expr::Parened(e) => is_trivial(e),35			_ => false,36		}37	}38	Some(match &*expr.0 {39		Expr::Str(s) => Val::Str(StrValue::Flat(s.clone())),40		Expr::Num(n) => Val::Num(*n),41		Expr::Literal(LiteralType::False) => Val::Bool(false),42		Expr::Literal(LiteralType::True) => Val::Bool(true),43		Expr::Literal(LiteralType::Null) => Val::Null,44		Expr::Arr(n) => {45			if n.iter().any(|e| !is_trivial(e)) {46				return None;47			}48			Val::Arr(ArrValue::eager(49				n.iter()50					.map(evaluate_trivial)51					.map(|e| e.expect("checked trivial"))52					.collect(),53			))54		}55		Expr::Parened(e) => evaluate_trivial(e)?,56		_ => return None,57	})58}5960pub fn evaluate_method(ctx: Context, name: IStr, params: ParamsDesc, body: LocExpr) -> Val {61	Val::Func(FuncVal::Normal(Cc::new(FuncDesc {62		name,63		ctx,64		params,65		body,66	})))67}6869pub fn evaluate_field_name(ctx: Context, field_name: &FieldName) -> Result<Option<IStr>> {70	Ok(match field_name {71		FieldName::Fixed(n) => Some(n.clone()),72		FieldName::Dyn(expr) => State::push(73			CallLocation::new(&expr.1),74			|| "evaluating field name".to_string(),75			|| {76				let value = evaluate(ctx, expr)?;77				if matches!(value, Val::Null) {78					Ok(None)79				} else {80					Ok(Some(IStr::from_untyped(value)?))81				}82			},83		)?,84	})85}8687pub fn evaluate_comp(88	ctx: Context,89	specs: &[CompSpec],90	callback: &mut impl FnMut(Context) -> Result<()>,91) -> Result<()> {92	match specs.get(0) {93		None => callback(ctx)?,94		Some(CompSpec::IfSpec(IfSpecData(cond))) => {95			if bool::from_untyped(evaluate(ctx.clone(), cond)?)? {96				evaluate_comp(ctx, &specs[1..], callback)?;97			}98		}99		Some(CompSpec::ForSpec(ForSpecData(var, expr))) => match evaluate(ctx.clone(), expr)? {100			Val::Arr(list) => {101				for item in list.iter_lazy() {102					let fctx = Pending::new();103					let mut new_bindings = GcHashMap::with_capacity(var.capacity_hint());104					destruct(var, item, fctx.clone(), &mut new_bindings)?;105					let ctx = ctx106						.clone()107						.extend(new_bindings, None, None, None)108						.into_future(fctx);109110					evaluate_comp(ctx, &specs[1..], callback)?;111				}112			}113			#[cfg(feature = "exp-object-iteration")]114			Val::Obj(obj) => {115				for field in obj.fields(116					// TODO: Should there be ability to preserve iteration order?117					#[cfg(feature = "exp-preserve-order")]118					false,119				) {120					#[derive(Trace)]121					struct ObjectFieldThunk {122						obj: ObjValue,123						field: IStr,124					}125					impl ThunkValue for ObjectFieldThunk {126						type Output = Val;127128						fn get(self: Box<Self>) -> Result<Self::Output> {129							self.obj.get(self.field).transpose().expect(130								"field exists, as field name was obtained from object.fields()",131							)132						}133					}134135					let fctx = Pending::new();136					let mut new_bindings = GcHashMap::with_capacity(var.capacity_hint());137					let value = Thunk::evaluated(Val::Arr(ArrValue::lazy(Cc::new(vec![138						Thunk::evaluated(Val::Str(StrValue::Flat(field.clone()))),139						Thunk::new(ObjectFieldThunk {140							field: field.clone(),141							obj: obj.clone(),142						}),143					]))));144					destruct(var, value, fctx.clone(), &mut new_bindings)?;145					let ctx = ctx146						.clone()147						.extend(new_bindings, None, None, None)148						.into_future(fctx);149150					evaluate_comp(ctx, &specs[1..], callback)?;151				}152			}153			_ => throw!(InComprehensionCanOnlyIterateOverArray),154		},155	}156	Ok(())157}158159trait CloneableUnbound<T>: Unbound<Bound = T> + Clone {}160impl<V, T> CloneableUnbound<T> for V where V: Unbound<Bound = T> + Clone {}161162fn evaluate_object_locals(163	fctx: Pending<Context>,164	locals: Rc<Vec<BindSpec>>,165) -> impl CloneableUnbound<Context> {166	#[derive(Trace, Clone)]167	struct UnboundLocals {168		fctx: Pending<Context>,169		locals: Rc<Vec<BindSpec>>,170	}171	impl Unbound for UnboundLocals {172		type Bound = Context;173174		fn bind(&self, sup: Option<ObjValue>, this: Option<ObjValue>) -> Result<Context> {175			let fctx = Context::new_future();176			let mut new_bindings =177				GcHashMap::with_capacity(self.locals.iter().map(BindSpec::capacity_hint).sum());178			for b in self.locals.iter() {179				evaluate_dest(b, fctx.clone(), &mut new_bindings)?;180			}181182			let ctx = self.fctx.unwrap();183			let new_dollar = ctx.dollar().cloned().or_else(|| this.clone());184185			let ctx = ctx186				.extend(new_bindings, new_dollar, sup, this)187				.into_future(fctx);188189			Ok(ctx)190		}191	}192193	UnboundLocals { fctx, locals }194}195196pub fn evaluate_field_member<B: Unbound<Bound = Context> + Clone>(197	builder: &mut ObjValueBuilder,198	ctx: Context,199	uctx: B,200	field: &FieldMember,201) -> Result<()> {202	let name = evaluate_field_name(ctx, &field.name)?;203	let Some(name) = name else {204		return Ok(());205	};206207	match field {208		FieldMember {209			plus,210			params: None,211			visibility,212			value,213			..214		} => {215			#[derive(Trace)]216			struct UnboundValue<B: Trace> {217				uctx: B,218				value: LocExpr,219				name: IStr,220			}221			impl<B: Unbound<Bound = Context>> Unbound for UnboundValue<B> {222				type Bound = Val;223				fn bind(&self, sup: Option<ObjValue>, this: Option<ObjValue>) -> Result<Val> {224					evaluate_named(self.uctx.bind(sup, this)?, &self.value, self.name.clone())225				}226			}227228			builder229				.member(name.clone())230				.with_add(*plus)231				.with_visibility(*visibility)232				.with_location(value.1.clone())233				.bindable(UnboundValue {234					uctx,235					value: value.clone(),236					name,237				})?;238		}239		FieldMember {240			params: Some(params),241			visibility,242			value,243			..244		} => {245			#[derive(Trace)]246			struct UnboundMethod<B: Trace> {247				uctx: B,248				value: LocExpr,249				params: ParamsDesc,250				name: IStr,251			}252			impl<B: Unbound<Bound = Context>> Unbound for UnboundMethod<B> {253				type Bound = Val;254				fn bind(&self, sup: Option<ObjValue>, this: Option<ObjValue>) -> Result<Val> {255					Ok(evaluate_method(256						self.uctx.bind(sup, this)?,257						self.name.clone(),258						self.params.clone(),259						self.value.clone(),260					))261				}262			}263264			builder265				.member(name.clone())266				.with_visibility(*visibility)267				.with_location(value.1.clone())268				.bindable(UnboundMethod {269					uctx,270					value: value.clone(),271					params: params.clone(),272					name,273				})?;274		}275	}276	Ok(())277}278279#[allow(clippy::too_many_lines)]280pub fn evaluate_member_list_object(ctx: Context, members: &[Member]) -> Result<ObjValue> {281	let mut builder = ObjValueBuilder::new();282	let locals = Rc::new(283		members284			.iter()285			.filter_map(|m| match m {286				Member::BindStmt(bind) => Some(bind.clone()),287				_ => None,288			})289			.collect::<Vec<_>>(),290	);291292	let fctx = Context::new_future();293294	// We have single context for all fields, so we can cache binds295	let uctx = CachedUnbound::new(evaluate_object_locals(fctx.clone(), locals));296297	for member in members.iter() {298		match member {299			Member::Field(field) => {300				evaluate_field_member(&mut builder, ctx.clone(), uctx.clone(), field)?;301			}302			Member::AssertStmt(stmt) => {303				#[derive(Trace)]304				struct ObjectAssert<B: Trace> {305					uctx: B,306					assert: AssertStmt,307				}308				impl<B: Unbound<Bound = Context>> ObjectAssertion for ObjectAssert<B> {309					fn run(&self, sup: Option<ObjValue>, this: Option<ObjValue>) -> Result<()> {310						let ctx = self.uctx.bind(sup, this)?;311						evaluate_assert(ctx, &self.assert)312					}313				}314				builder.assert(ObjectAssert {315					uctx: uctx.clone(),316					assert: stmt.clone(),317				});318			}319			Member::BindStmt(_) => {320				// Already handled321			}322		}323	}324	let this = builder.build();325	fctx.fill(ctx.extend(GcHashMap::new(), None, None, Some(this.clone())));326	Ok(this)327}328329pub fn evaluate_object(ctx: Context, object: &ObjBody) -> Result<ObjValue> {330	Ok(match object {331		ObjBody::MemberList(members) => evaluate_member_list_object(ctx, members)?,332		ObjBody::ObjComp(obj) => {333			let mut builder = ObjValueBuilder::new();334			let locals = Rc::new(335				obj.pre_locals336					.iter()337					.chain(obj.post_locals.iter())338					.cloned()339					.collect::<Vec<_>>(),340			);341			let mut ctxs = vec![];342			evaluate_comp(ctx, &obj.compspecs, &mut |ctx| {343				let fctx = Context::new_future();344				ctxs.push((ctx.clone(), fctx.clone()));345				let uctx = evaluate_object_locals(fctx, locals.clone());346347				evaluate_field_member(&mut builder, ctx, uctx, &obj.field)348			})?;349350			let this = builder.build();351			for (ctx, fctx) in ctxs {352				let _ctx = ctx353					.extend(GcHashMap::new(), None, None, Some(this.clone()))354					.into_future(fctx);355			}356			this357		}358	})359}360361pub fn evaluate_apply(362	ctx: Context,363	value: &LocExpr,364	args: &ArgsDesc,365	loc: CallLocation<'_>,366	tailstrict: bool,367) -> Result<Val> {368	let value = evaluate(ctx.clone(), value)?;369	Ok(match value {370		Val::Func(f) => {371			let body = || f.evaluate(ctx, loc, args, tailstrict);372			if tailstrict {373				body()?374			} else {375				State::push(loc, || format!("function <{}> call", f.name()), body)?376			}377		}378		v => throw!(OnlyFunctionsCanBeCalledGot(v.value_type())),379	})380}381382pub fn evaluate_assert(ctx: Context, assertion: &AssertStmt) -> Result<()> {383	let value = &assertion.0;384	let msg = &assertion.1;385	let assertion_result = State::push(386		CallLocation::new(&value.1),387		|| "assertion condition".to_owned(),388		|| bool::from_untyped(evaluate(ctx.clone(), value)?),389	)?;390	if !assertion_result {391		State::push(392			CallLocation::new(&value.1),393			|| "assertion failure".to_owned(),394			|| {395				if let Some(msg) = msg {396					throw!(AssertionFailed(evaluate(ctx, msg)?.to_string()?));397				}398				throw!(AssertionFailed(Val::Null.to_string()?));399			},400		)?;401	}402	Ok(())403}404405pub fn evaluate_named(ctx: Context, expr: &LocExpr, name: IStr) -> Result<Val> {406	use Expr::*;407	let LocExpr(raw_expr, _loc) = expr;408	Ok(match &**raw_expr {409		Function(params, body) => evaluate_method(ctx, name, params.clone(), body.clone()),410		_ => evaluate(ctx, expr)?,411	})412}413414#[allow(clippy::too_many_lines)]415pub fn evaluate(ctx: Context, expr: &LocExpr) -> Result<Val> {416	use Expr::*;417418	if let Some(trivial) = evaluate_trivial(expr) {419		return Ok(trivial);420	}421	let LocExpr(expr, loc) = expr;422	Ok(match &**expr {423		Literal(LiteralType::This) => {424			Val::Obj(ctx.this().ok_or(CantUseSelfOutsideOfObject)?.clone())425		}426		Literal(LiteralType::Super) => Val::Obj(427			ctx.super_obj().ok_or(NoSuperFound)?.with_this(428				ctx.this()429					.expect("if super exists - then this should too")430					.clone(),431			),432		),433		Literal(LiteralType::Dollar) => {434			Val::Obj(ctx.dollar().ok_or(NoTopLevelObjectFound)?.clone())435		}436		Literal(LiteralType::True) => Val::Bool(true),437		Literal(LiteralType::False) => Val::Bool(false),438		Literal(LiteralType::Null) => Val::Null,439		Parened(e) => evaluate(ctx, e)?,440		Str(v) => Val::Str(StrValue::Flat(v.clone())),441		Num(v) => Val::new_checked_num(*v)?,442		BinaryOp(v1, o, v2) => evaluate_binary_op_special(ctx, v1, *o, v2)?,443		UnaryOp(o, v) => evaluate_unary_op(*o, &evaluate(ctx, v)?)?,444		Var(name) => State::push(445			CallLocation::new(loc),446			|| format!("variable <{name}> access"),447			|| ctx.binding(name.clone())?.evaluate(),448		)?,449		Index(LocExpr(v, _), index) if matches!(&**v, Expr::Literal(LiteralType::Super)) => {450			let name = evaluate(ctx.clone(), index)?;451			let Val::Str(name) = name else {452				throw!(ValueIndexMustBeTypeGot(453					ValType::Obj,454					ValType::Str,455					name.value_type(),456				))457			};458			ctx.super_obj()459				.expect("no super found")460				.get_for(name.into_flat(), ctx.this().expect("no this found").clone())?461				.expect("value not found")462		}463		Index(value, index) => match (evaluate(ctx.clone(), value)?, evaluate(ctx, index)?) {464			(Val::Obj(v), Val::Str(key)) => State::push(465				CallLocation::new(loc),466				|| format!("field <{key}> access"),467				|| match v.get(key.clone().into_flat()) {468					Ok(Some(v)) => Ok(v),469					Ok(None) => {470						let suggestions = suggest_object_fields(&v, key.clone().into_flat());471472						throw!(NoSuchField(key.clone().into_flat(), suggestions))473					}474					Err(e) => Err(e),475				},476			)?,477			(Val::Obj(_), n) => throw!(ValueIndexMustBeTypeGot(478				ValType::Obj,479				ValType::Str,480				n.value_type(),481			)),482483			(Val::Arr(v), Val::Num(n)) => {484				if n.fract() > f64::EPSILON {485					throw!(FractionalIndex)486				}487				v.get(n as usize)?488					.ok_or_else(|| ArrayBoundsError(n as usize, v.len()))?489			}490			(Val::Arr(_), Val::Str(n)) => throw!(AttemptedIndexAnArrayWithString(n.into_flat())),491			(Val::Arr(_), n) => throw!(ValueIndexMustBeTypeGot(492				ValType::Arr,493				ValType::Num,494				n.value_type(),495			)),496497			(Val::Str(s), Val::Num(n)) => Val::Str({498				let v: IStr = s499					.clone()500					.into_flat()501					.chars()502					.skip(n as usize)503					.take(1)504					.collect::<String>()505					.into();506				if v.is_empty() {507					let size = s.into_flat().chars().count();508					throw!(StringBoundsError(n as usize, size))509				}510				StrValue::Flat(v)511			}),512			(Val::Str(_), n) => throw!(ValueIndexMustBeTypeGot(513				ValType::Str,514				ValType::Num,515				n.value_type(),516			)),517518			(v, _) => throw!(CantIndexInto(v.value_type())),519		},520		LocalExpr(bindings, returned) => {521			let mut new_bindings: GcHashMap<IStr, Thunk<Val>> =522				GcHashMap::with_capacity(bindings.iter().map(BindSpec::capacity_hint).sum());523			let fctx = Context::new_future();524			for b in bindings {525				evaluate_dest(b, fctx.clone(), &mut new_bindings)?;526			}527			let ctx = ctx.extend(new_bindings, None, None, None).into_future(fctx);528			evaluate(ctx, &returned.clone())?529		}530		Arr(items) => {531			if items.is_empty() {532				Val::Arr(ArrValue::empty())533			} else if items.len() == 1 {534				#[derive(Trace)]535				struct ArrayElement {536					ctx: Context,537					item: LocExpr,538				}539				impl ThunkValue for ArrayElement {540					type Output = Val;541					fn get(self: Box<Self>) -> Result<Val> {542						evaluate(self.ctx, &self.item)543					}544				}545				Val::Arr(ArrValue::lazy(Cc::new(vec![Thunk::new(ArrayElement {546					ctx,547					item: items[0].clone(),548				})])))549			} else {550				Val::Arr(ArrValue::expr(ctx, items.iter().cloned()))551			}552		}553		ArrComp(expr, comp_specs) => {554			let mut out = Vec::new();555			evaluate_comp(ctx, comp_specs, &mut |ctx| {556				out.push(evaluate(ctx, expr)?);557				Ok(())558			})?;559			Val::Arr(ArrValue::eager(out))560		}561		Obj(body) => Val::Obj(evaluate_object(ctx, body)?),562		ObjExtend(a, b) => evaluate_add_op(563			&evaluate(ctx.clone(), a)?,564			&Val::Obj(evaluate_object(ctx, b)?),565		)?,566		Apply(value, args, tailstrict) => {567			evaluate_apply(ctx, value, args, CallLocation::new(loc), *tailstrict)?568		}569		Function(params, body) => {570			evaluate_method(ctx, "anonymous".into(), params.clone(), body.clone())571		}572		AssertExpr(assert, returned) => {573			evaluate_assert(ctx.clone(), assert)?;574			evaluate(ctx, returned)?575		}576		ErrorStmt(e) => State::push(577			CallLocation::new(loc),578			|| "error statement".to_owned(),579			|| throw!(RuntimeError(evaluate(ctx, e)?.to_string()?,)),580		)?,581		IfElse {582			cond,583			cond_then,584			cond_else,585		} => {586			if State::push(587				CallLocation::new(loc),588				|| "if condition".to_owned(),589				|| bool::from_untyped(evaluate(ctx.clone(), &cond.0)?),590			)? {591				evaluate(ctx, cond_then)?592			} else {593				match cond_else {594					Some(v) => evaluate(ctx, v)?,595					None => Val::Null,596				}597			}598		}599		Slice(value, desc) => {600			fn parse_idx<T: Typed>(601				loc: CallLocation<'_>,602				ctx: &Context,603				expr: Option<&LocExpr>,604				desc: &'static str,605			) -> Result<Option<T>> {606				if let Some(value) = expr {607					Ok(Some(State::push(608						loc,609						|| format!("slice {desc}"),610						|| T::from_untyped(evaluate(ctx.clone(), value)?),611					)?))612				} else {613					Ok(None)614				}615			}616617			let indexable = evaluate(ctx.clone(), value)?;618			let loc = CallLocation::new(loc);619620			let start = parse_idx(loc, &ctx, desc.start.as_ref(), "start")?;621			let end = parse_idx(loc, &ctx, desc.end.as_ref(), "end")?;622			let step = parse_idx(loc, &ctx, desc.step.as_ref(), "step")?;623624			IndexableVal::into_untyped(indexable.into_indexable()?.slice(start, end, step)?)?625		}626		i @ (Import(path) | ImportStr(path) | ImportBin(path)) => {627			let Expr::Str(path) = &*path.0 else {628				throw!("computed imports are not supported")629			};630			let tmp = loc.clone().0;631			let s = ctx.state();632			let resolved_path = s.resolve_from(tmp.source_path(), path as &str)?;633			match i {634				Import(_) => State::push(635					CallLocation::new(loc),636					|| format!("import {:?}", path.clone()),637					|| s.import_resolved(resolved_path),638				)?,639				ImportStr(_) => Val::Str(StrValue::Flat(s.import_resolved_str(resolved_path)?)),640				ImportBin(_) => Val::Arr(ArrValue::bytes(s.import_resolved_bin(resolved_path)?)),641				_ => unreachable!(),642			}643		}644	})645}
modifiedcrates/jrsonnet-evaluator/src/evaluate/operator.rsdiffbeforeafterboth
--- a/crates/jrsonnet-evaluator/src/evaluate/operator.rs
+++ b/crates/jrsonnet-evaluator/src/evaluate/operator.rs
@@ -88,6 +88,10 @@
 	Ok(match (evaluate(ctx.clone(), a)?, op, b) {
 		(Bool(true), Or, _o) => Val::Bool(true),
 		(Bool(false), And, _o) => Val::Bool(false),
+		#[cfg(feature = "exp-null-coaelse")]
+		(Null, NullCoaelse, eb) => evaluate(ctx, eb)?,
+		#[cfg(feature = "exp-null-coaelse")]
+		(a, NullCoaelse, _o) => a,
 		(a, op, eb) => evaluate_binary_op_normal(&a, op, &evaluate(ctx, eb)?)?,
 	})
 }
modifiedcrates/jrsonnet-parser/Cargo.tomldiffbeforeafterboth
--- a/crates/jrsonnet-parser/Cargo.toml
+++ b/crates/jrsonnet-parser/Cargo.toml
@@ -10,6 +10,7 @@
 [features]
 default = []
 exp-destruct = []
+exp-null-coaelse = []
 # Implement serialization of AST using structdump
 #
 # Structdump generates code, which exactly replicated passed AST
modifiedcrates/jrsonnet-parser/src/expr.rsdiffbeforeafterboth
--- a/crates/jrsonnet-parser/src/expr.rs
+++ b/crates/jrsonnet-parser/src/expr.rs
@@ -122,6 +122,8 @@
 
 	And,
 	Or,
+	#[cfg(feature = "exp-null-coaelse")]
+	NullCoaelse,
 
 	// Equialent to std.objectHasEx(a, b, true)
 	In,
@@ -153,6 +155,8 @@
 				And => "&&",
 				Or => "||",
 				In => "in",
+				#[cfg(feature = "exp-null-coaelse")]
+				NullCoaelse => "??",
 			}
 		)
 	}
@@ -399,8 +403,13 @@
 	ErrorStmt(LocExpr),
 	/// a(b, c)
 	Apply(LocExpr, ArgsDesc, bool),
-	/// a[b]
-	Index(LocExpr, LocExpr),
+	/// a[b], a.b, a?.b
+	Index {
+		indexable: LocExpr,
+		index: LocExpr,
+		#[cfg(feature = "exp-null-coaelse")]
+		null_coaelse: bool,
+	},
 	/// function(x) x
 	Function(ParamsDesc, LocExpr),
 	/// if true == false then 1 else 2
modifiedcrates/jrsonnet-parser/src/lib.rsdiffbeforeafterboth
--- a/crates/jrsonnet-parser/src/lib.rs
+++ b/crates/jrsonnet-parser/src/lib.rs
@@ -288,7 +288,11 @@
 		rule unaryop(x: rule<()>) -> ()
 			= quiet!{ x() } / expected!("<unary op>")
 
-
+		rule ensure_null_coaelse()
+			= "" {?
+				#[cfg(not(feature = "exp-null-coaelse"))] return Err("!!!experimental null coaelscing was not enabled");
+				#[cfg(feature = "exp-null-coaelse")] Ok(())
+			}
 		use BinaryOpType::*;
 		use UnaryOpType::*;
 		rule expr(s: &ParserSettings) -> LocExpr
@@ -296,6 +300,10 @@
 				start:position!() v:@ end:position!() { LocExpr(Rc::new(v), ExprLocation(s.source.clone(), start as u32, end as u32)) }
 				--
 				a:(@) _ binop(<"||">) _ b:@ {expr_bin!(a Or b)}
+				a:(@) _ binop(<"??">) _ ensure_null_coaelse() b:@ {
+					#[cfg(feature = "exp-null-coaelse")] return expr_bin!(a NullCoaelse b);
+					unreachable!("ensure_null_coaelse will fail if feature is not enabled")
+				}
 				--
 				a:(@) _ binop(<"&&">) _ b:@ {expr_bin!(a And b)}
 				--
@@ -329,8 +337,16 @@
 						unaryop(<"~">) _ b:@ {expr_un!(BitNot b)}
 				--
 				a:(@) _ "[" _ e:slice_desc(s) _ "]" {Expr::Slice(a, e)}
-				a:(@) _ "." _ a:position!() e:id_loc(s) b:position!() {Expr::Index(a, e)}
-				a:(@) _ "[" _ e:expr(s) _ "]" {Expr::Index(a, e)}
+				indexable:(@) _ null_coaelse:("?" _ ensure_null_coaelse())? "."  _ index:id_loc(s) {Expr::Index{
+					indexable, index,
+					#[cfg(feature = "exp-null-coaelse")]
+					null_coaelse: null_coaelse.is_some(),
+				}}
+				indexable:(@) _ null_coaelse:("?" _ "." _ ensure_null_coaelse())? "[" _ index:expr(s) _ "]" {Expr::Index{
+					indexable, index,
+					#[cfg(feature = "exp-null-coaelse")]
+					null_coaelse: null_coaelse.is_some(),
+				}}
 				a:(@) _ "(" _ args:args(s) _ ")" ts:(_ keyword("tailstrict"))? {Expr::Apply(a, args, ts.is_some())}
 				a:(@) _ "{" _ body:objinside(s) _ "}" {Expr::ObjExtend(a, body)}
 				--