ast: ranges for accessors in single-line flow strings (#231)

These changes add support for reporting ranges for accessors in
single-line flow strings (i.e. single-line strings that are not quoted).

Multi-line strings are quite a bit more complicated to support. The
string we get from the YAML parser has already been processed to remove
indentation, fold newlines, etc., so its bytes do not represent the
bytes in the original file. We will want to add support for these
strings in the future, but doing so is something of an open problem.

Fixes #232.

Author: pgavlin

CHANGELOG_PENDING.md

@@ -9,4 +9,7 @@
 - Improve property accessor diagnostics.
   [#230](https://github.com/pulumi/esc/pull/230)
 
+- Populate source positions for property accessors in single-line flow scalars.
+  [#231](https://github.com/pulumi/esc/pull/231)
+
 ### Bug Fixes

ast/expr.go

@@ -52,16 +52,31 @@ func (x *exprNode) Syntax() syntax.Node {
 	return x.syntax
 }
 
-// ExprError creates an error-level diagnostic associated with the given expression. If the expression is non-nil and
-// has an underlying syntax node, the error will cover the underlying textual range.
-func ExprError(expr Expr, summary string) *syntax.Diagnostic {
-	var rng *hcl.Range
+func exprPosition(expr Expr) (*hcl.Range, string) {
 	if expr != nil {
 		if syntax := expr.Syntax(); syntax != nil {
-			rng = syntax.Syntax().Range()
+			return syntax.Syntax().Range(), syntax.Syntax().Path()
 		}
 	}
-	return syntax.Error(rng, summary, expr.Syntax().Syntax().Path())
+	return nil, ""
+}
+
+// ExprError creates an error-level diagnostic associated with the given expression. If the expression is non-nil and
+// has an underlying syntax node, the error will cover the underlying textual range.
+func ExprError(expr Expr, summary string) *syntax.Diagnostic {
+	rng, path := exprPosition(expr)
+	return syntax.Error(rng, summary, path)
+}
+
+// AccessorError creates an error-level diagnostic associated with the given expression and accessor. If the accessor
+// has range information, the error will cover its textual range. Otherwise, the error will cover the textual range of
+// the parent expression.
+func AccessorError(parent Expr, accessor PropertyAccessor, summary string) *syntax.Diagnostic {
+	rng, path := exprPosition(parent)
+	if r := accessor.Range(); r != nil {
+		rng = r
+	}
+	return syntax.Error(rng, summary, path)
 }
 
 // A NullExpr represents a null literal.

ast/interpolation.go

@@ -29,13 +29,14 @@ func parseInterpolate(node syntax.Node, value string) ([]Interpolation, syntax.D
 	var parts []Interpolation
 	var str strings.Builder
 	var diags syntax.Diagnostics
+	offset := 0
 	for len(value) > 0 {
 		switch {
 		case strings.HasPrefix(value, "$$"):
 			str.WriteByte('$')
-			value = value[2:]
+			value, offset = value[2:], offset+2
 		case strings.HasPrefix(value, "${"):
-			rest, access, accessDiags := parsePropertyAccess(node, value[2:])
+			end, rest, access, accessDiags := parsePropertyAccess(node, offset+2, value[2:])
 
 			diags.Extend(accessDiags...)
 			parts = append(parts, Interpolation{
@@ -44,10 +45,10 @@ func parseInterpolate(node syntax.Node, value string) ([]Interpolation, syntax.D
 			})
 			str.Reset()
 
-			value = rest
+			value, offset = rest, end
 		default:
 			str.WriteByte(value[0])
-			value = value[1:]
+			value, offset = value[1:], offset+1
 		}
 	}
 	if str.Len() != 0 {

ast/interpolation_test.go

@@ -17,10 +17,32 @@ package ast
 import (
 	"testing"
 
+	"github.com/hashicorp/hcl/v2"
 	"github.com/pulumi/esc/syntax"
 	"github.com/stretchr/testify/assert"
 )
 
+type SimpleScalar string
+
+func (s SimpleScalar) Range() *hcl.Range {
+	return &hcl.Range{
+		Start: hcl.Pos{},
+		End:   hcl.Pos{Byte: len(s)},
+	}
+}
+
+func (s SimpleScalar) Path() string {
+	return "test"
+}
+
+func (s SimpleScalar) ScalarRange(start, end int) *hcl.Range {
+	r := s.Range()
+	return &hcl.Range{
+		Start: hcl.Pos{Byte: r.Start.Byte + start},
+		End:   hcl.Pos{Byte: r.Start.Byte + end},
+	}
+}
+
 func mkInterp(text string, accessors ...PropertyAccessor) Interpolation {
 	return Interpolation{
 		Text:  text,
@@ -35,12 +57,24 @@ func mkAccess(accessors ...PropertyAccessor) *PropertyAccess {
 	return &PropertyAccess{Accessors: accessors}
 }
 
-func mkPropertyName(name string) *PropertyName {
-	return &PropertyName{Name: name}
+func mkPropertyName(name string, start, end int) *PropertyName {
+	return &PropertyName{
+		Name: name,
+		AccessorRange: &hcl.Range{
+			Start: hcl.Pos{Byte: start},
+			End:   hcl.Pos{Byte: end},
+		},
+	}
 }
 
-func mkPropertySubscript[T string | int](index T) *PropertySubscript {
-	return &PropertySubscript{Index: index}
+func mkPropertySubscript[T string | int](index T, start, end int) *PropertySubscript {
+	return &PropertySubscript{
+		Index: index,
+		AccessorRange: &hcl.Range{
+			Start: hcl.Pos{Byte: start},
+			End:   hcl.Pos{Byte: end},
+		},
+	}
 }
 
 func TestInvalidInterpolations(t *testing.T) {
@@ -50,51 +84,51 @@ func TestInvalidInterpolations(t *testing.T) {
 	}{
 		{
 			text:  "${foo",
-			parts: []Interpolation{mkInterp("", mkPropertyName("foo"))},
+			parts: []Interpolation{mkInterp("", mkPropertyName("foo", 2, 5))},
 		},
 		{
 			text: "${foo ",
 			parts: []Interpolation{
-				mkInterp("", mkPropertyName("foo")),
+				mkInterp("", mkPropertyName("foo", 2, 5)),
 				mkInterp(" "),
 			},
 		},
 		{
 			text: `${foo} ${["baz} bar`,
 			parts: []Interpolation{
-				mkInterp("", mkPropertyName("foo")),
-				mkInterp(" ", mkPropertySubscript("baz} bar")),
+				mkInterp("", mkPropertyName("foo", 2, 5)),
+				mkInterp(" ", mkPropertySubscript("baz} bar", 9, 19)),
 			},
 		},
 		{
 			text: `missing ${property[} subscript`,
 			parts: []Interpolation{
-				mkInterp("missing ", mkPropertyName("property"), mkPropertySubscript("")),
+				mkInterp("missing ", mkPropertyName("property", 10, 18), mkPropertySubscript("", 18, 19)),
 				mkInterp(" subscript"),
 			},
 		},
 		{
 			text: `${[bar].baz}`,
 			parts: []Interpolation{
-				mkInterp("", mkPropertySubscript("bar"), mkPropertyName("baz")),
+				mkInterp("", mkPropertySubscript("bar", 2, 7), mkPropertyName("baz", 7, 11)),
 			},
 		},
 		{
 			text: `${foo.`,
 			parts: []Interpolation{
-				mkInterp("", mkPropertyName("foo"), mkPropertyName("")),
+				mkInterp("", mkPropertyName("foo", 2, 5), mkPropertyName("", 5, 6)),
 			},
 		},
 		{
 			text: `${foo[`,
 			parts: []Interpolation{
-				mkInterp("", mkPropertyName("foo"), mkPropertySubscript("")),
+				mkInterp("", mkPropertyName("foo", 2, 5), mkPropertySubscript("", 5, 6)),
 			},
 		},
 	}
 	for _, c := range cases {
 		t.Run(c.text, func(t *testing.T) {
-			node := syntax.String(c.text)
+			node := syntax.StringSyntax(SimpleScalar(c.text), c.text)
 			parts, diags := parseInterpolate(node, c.text)
 			assert.NotEmpty(t, diags)
 			assert.Equal(t, c.parts, parts)