decoder: Add support for List as Constraint

decoder/expr_list.go

@@ -1,10 +1,6 @@
 package decoder
 
 import (
-	"context"
-
-	"github.com/hashicorp/hcl-lang/lang"
-	"github.com/hashicorp/hcl-lang/reference"
 	"github.com/hashicorp/hcl-lang/schema"
 	"github.com/hashicorp/hcl/v2"
 )
@@ -14,28 +10,3 @@ type List struct {
 	cons    schema.List
 	pathCtx *PathContext
 }
-
-func (l List) CompletionAtPos(ctx context.Context, pos hcl.Pos) []lang.Candidate {
-	// TODO
-	return nil
-}
-
-func (l List) HoverAtPos(ctx context.Context, pos hcl.Pos) *lang.HoverData {
-	// TODO
-	return nil
-}
-
-func (l List) SemanticTokens(ctx context.Context) []lang.SemanticToken {
-	// TODO
-	return nil
-}
-
-func (l List) ReferenceOrigins(ctx context.Context, allowSelfRefs bool) reference.Origins {
-	// TODO
-	return nil
-}
-
-func (l List) ReferenceTargets(ctx context.Context, targetCtx *TargetContext) reference.Targets {
-	// TODO
-	return nil
-}

decoder/expr_list_completion.go

@@ -0,0 +1,84 @@
+package decoder
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/hashicorp/hcl-lang/lang"
+	"github.com/hashicorp/hcl/v2"
+	"github.com/hashicorp/hcl/v2/hclsyntax"
+)
+
+func (list List) CompletionAtPos(ctx context.Context, pos hcl.Pos) []lang.Candidate {
+	if isEmptyExpression(list.expr) {
+		label := "[ ]"
+
+		if list.cons.Elem != nil {
+			label = fmt.Sprintf("[ %s ]", list.cons.Elem.FriendlyName())
+		}
+
+		d := list.cons.EmptyCompletionData(1, 0)
+
+		return []lang.Candidate{
+			{
+				Label:       label,
+				Detail:      list.cons.FriendlyName(),
+				Kind:        lang.ListCandidateKind,
+				Description: list.cons.Description,
+				TextEdit: lang.TextEdit{
+					NewText: d.NewText,
+					Snippet: d.Snippet,
+					Range: hcl.Range{
+						Filename: list.expr.Range().Filename,
+						Start:    pos,
+						End:      pos,
+					},
+				},
+				TriggerSuggest: d.TriggerSuggest,
+			},
+		}
+	}
+
+	eType, ok := list.expr.(*hclsyntax.TupleConsExpr)
+	if !ok {
+		return []lang.Candidate{}
+	}
+
+	if list.cons.Elem == nil {
+		return []lang.Candidate{}
+	}
+
+	betweenBraces := hcl.Range{
+		Filename: eType.Range().Filename,
+		Start:    eType.OpenRange.End,
+		End:      eType.Range().End,
+	}
+
+	if betweenBraces.ContainsPos(pos) {
+		if len(eType.Exprs) == 0 {
+			expr := newEmptyExpressionAtPos(eType.Range().Filename, pos)
+			return newExpression(list.pathCtx, expr, list.cons.Elem).CompletionAtPos(ctx, pos)
+		}
+
+		for _, elemExpr := range eType.Exprs {
+			// We cannot trust ranges of empty expressions, so we imply
+			// that invalid configuration follows and we stop here
+			// e.g. for completion between commas [keyword, ,keyword]
+			if isEmptyExpression(elemExpr) {
+				break
+			}
+			// We overshot the position and stop
+			if elemExpr.Range().Start.Byte > pos.Byte {
+				break
+			}
+			if elemExpr.Range().ContainsPos(pos) || elemExpr.Range().End.Byte == pos.Byte {
+				return newExpression(list.pathCtx, elemExpr, list.cons.Elem).CompletionAtPos(ctx, pos)
+			}
+		}
+
+		expr := newEmptyExpressionAtPos(eType.Range().Filename, pos)
+		return newExpression(list.pathCtx, expr, list.cons.Elem).CompletionAtPos(ctx, pos)
+	}
+
+	return []lang.Candidate{}
+}