zclsyntax: peeker pretends single-line comments are newlines

When we're skipping comments but retaining newlines, we need to do some
slight-of-hand because single-line comment tokens contain the newline
that terminates them (for simpler handling of lead doc comments) but our
parsing can be newline-sensitive.

To allow for this, as a special case we transform single-line comment
tokens into newlines when in this situation, thus allowing parser code
to just worry about the newlines and skip over the comments.

zcl/zclsyntax/parser.go

@@ -157,11 +157,14 @@ func (p *parser) finishParsingBodyAttribute(ident Token) (Node, zcl.Diagnostics)
 		panic("finishParsingBodyAttribute called with next not equals")
 	}
 
+	var endRange zcl.Range
+
 	expr, diags := p.ParseExpression()
 	if p.recovery && diags.HasErrors() {
 		// recovery within expressions tends to be tricky, so we've probably
 		// landed somewhere weird. We'll try to reset to the start of a body
 		// item so parsing can continue.
+		endRange = p.PrevRange()
 		p.recoverAfterBodyItem()
 	} else {
 		end := p.Peek()
@@ -175,14 +178,14 @@ func (p *parser) finishParsingBodyAttribute(ident Token) (Node, zcl.Diagnostics)
 					Context:  zcl.RangeBetween(ident.Range, end.Range).Ptr(),
 				})
 			}
+			endRange = p.PrevRange()
 			p.recoverAfterBodyItem()
 		} else {
+			endRange = p.PrevRange()
 			p.Read() // eat newline
 		}
 	}
 
-	endRange := p.PrevRange()
-
 	return &Attribute{
 		Name: string(ident.Bytes),
 		Expr: expr,

zcl/zclsyntax/parser_test.go

@@ -364,7 +364,7 @@ block "valid" {}
 		},
 
 		{
-			`a = 1`,
+			"a = 1\n",
 			0,
 			&Body{
 				Attributes: Attributes{
@@ -396,11 +396,11 @@ block "valid" {}
 				Blocks: Blocks{},
 				SrcRange: zcl.Range{
 					Start: zcl.Pos{Line: 1, Column: 1, Byte: 0},
-					End:   zcl.Pos{Line: 1, Column: 6, Byte: 5},
+					End:   zcl.Pos{Line: 2, Column: 1, Byte: 6},
 				},
 				EndRange: zcl.Range{
-					Start: zcl.Pos{Line: 1, Column: 6, Byte: 5},
+					Start: zcl.Pos{Line: 2, Column: 1, Byte: 6},
-					End:   zcl.Pos{Line: 1, Column: 6, Byte: 5},
+					End:   zcl.Pos{Line: 2, Column: 1, Byte: 6},
 				},
 			},
 		},
@@ -462,6 +462,47 @@ block "valid" {}
 				},
 			},
 		},
+		{
+			"a = 1 # line comment\n",
+			0,
+			&Body{
+				Attributes: Attributes{
+					"a": {
+						Name: "a",
+						Expr: &LiteralValueExpr{
+							Val: cty.NumberIntVal(1),
+
+							SrcRange: zcl.Range{
+								Start: zcl.Pos{Line: 1, Column: 5, Byte: 4},
+								End:   zcl.Pos{Line: 1, Column: 6, Byte: 5},
+							},
+						},
+
+						SrcRange: zcl.Range{
+							Start: zcl.Pos{Line: 1, Column: 1, Byte: 0},
+							End:   zcl.Pos{Line: 1, Column: 6, Byte: 5},
+						},
+						NameRange: zcl.Range{
+							Start: zcl.Pos{Line: 1, Column: 1, Byte: 0},
+							End:   zcl.Pos{Line: 1, Column: 2, Byte: 1},
+						},
+						EqualsRange: zcl.Range{
+							Start: zcl.Pos{Line: 1, Column: 3, Byte: 2},
+							End:   zcl.Pos{Line: 1, Column: 4, Byte: 3},
+						},
+					},
+				},
+				Blocks: Blocks{},
+				SrcRange: zcl.Range{
+					Start: zcl.Pos{Line: 1, Column: 1, Byte: 0},
+					End:   zcl.Pos{Line: 2, Column: 1, Byte: 21},
+				},
+				EndRange: zcl.Range{
+					Start: zcl.Pos{Line: 2, Column: 1, Byte: 21},
+					End:   zcl.Pos{Line: 2, Column: 1, Byte: 21},
+				},
+			},
+		},
 
 		{
 			`	`,

zcl/zclsyntax/peeker.go

@@ -50,6 +50,31 @@ func (p *peeker) nextToken() (Token, int) {
 		switch tok.Type {
 		case TokenComment:
 			if !p.IncludeComments {
+				// Single-line comment tokens, starting with # or //, absorb
+				// the trailing newline that terminates them as part of their
+				// bytes. When we're filtering out comments, we must as a
+				// special case transform these to newline tokens in order
+				// to properly parse newline-terminated block items.
+
+				if p.includingNewlines() {
+					if len(tok.Bytes) > 0 && tok.Bytes[len(tok.Bytes)-1] == '\n' {
+						fakeNewline := Token{
+							Type:  TokenNewline,
+							Bytes: tok.Bytes[len(tok.Bytes)-1 : len(tok.Bytes)],
+
+							// We use the whole token range as the newline
+							// range, even though that's a little... weird,
+							// because otherwise we'd need to go count
+							// characters again in order to figure out the
+							// column of the newline, and that complexity
+							// isn't justified when ranges of newlines are
+							// so rarely printed anyway.
+							Range: tok.Range,
+						}
+						return fakeNewline, i + 1
+					}
+				}
+
 				continue
 			}
 		case TokenNewline: