Method parseExpressionTraversals

hclsyntax/parser.go:625–926

(from Expression)

}

func (p *parser) parseExpressionTraversals(from Expression) (Expression, hcl.Diagnostics) {
	var diags hcl.Diagnostics
	ret := from

Traversal:
	for {
		next := p.Peek()

		switch next.Type {
		case TokenDot:
			// Attribute access or splat
			dot := p.Read()
			attrTok := p.Peek()

			switch attrTok.Type {
			case TokenIdent:
				attrTok = p.Read() // eat token
				name := string(attrTok.Bytes)
				rng := hcl.RangeBetween(dot.Range, attrTok.Range)
				step := hcl.TraverseAttr{
					Name:     name,
					SrcRange: rng,
				}

				ret = makeRelativeTraversal(ret, step, rng)

			case TokenNumberLit:
				// This is a weird form we inherited from HIL, allowing numbers
				// to be used as attributes as a weird way of writing [n].
				// This was never actually a first-class thing in HIL, but
				// HIL tolerated sequences like .0. in its variable names and
				// calling applications like Terraform exploited that to
				// introduce indexing syntax where none existed.
				numTok := p.Read() // eat token
				attrTok = numTok

				// This syntax is ambiguous if multiple indices are used in
				// succession, like foo.0.1.baz: that actually parses as
				// a fractional number 0.1. Since we're only supporting this
				// syntax for compatibility with legacy Terraform
				// configurations, and Terraform does not tend to have lists
				// of lists, we'll choose to reject that here with a helpful
				// error message, rather than failing later because the index
				// isn't a whole number.
				if dotIdx := bytes.IndexByte(numTok.Bytes, '.'); dotIdx >= 0 {
					first := numTok.Bytes[:dotIdx]
					second := numTok.Bytes[dotIdx+1:]
					diags = append(diags, &hcl.Diagnostic{
						Severity: hcl.DiagError,
						Summary:  "Invalid legacy index syntax",
						Detail:   fmt.Sprintf("When using the legacy index syntax, chaining two indexes together is not permitted. Use the proper index syntax instead, like [%s][%s].", first, second),
						Subject:  &attrTok.Range,
					})
					rng := hcl.RangeBetween(dot.Range, numTok.Range)
					step := hcl.TraverseIndex{
						Key:      cty.DynamicVal,
						SrcRange: rng,
					}