show code snippet when only line number is known

rhysd · rhysd · commit 3c605c16d55d · 2021-07-01T12:14:49.000+09:00
column is zero in the case. this happens when the error came from
go-yaml parser.
diff --git a/error.go b/error.go
@@ -68,7 +68,7 @@ func (e *Error) PrettyPrint(w io.Writer, source []byte) {
 	bold.Fprint(w, e.Message)
 	gray.Fprintf(w, " [%s]\n", e.Kind)
 
-	if len(source) == 0 || e.Line <= 0 || e.Column <= 0 {
+	if len(source) == 0 || e.Line <= 0 {
 		return
 	}
 	line, ok := e.getLine(source)
@@ -98,6 +98,10 @@ func (e *Error) getLine(source []byte) (string, bool) {
 }
 
 func (e *Error) getIndicator(line string) string {
+	if e.Column <= 0 {
+		return ""
+	}
+
 	start := e.Column - 1 // Column is 1-based
 
 	// Count width of non-space characters after '^' for underline
diff --git a/error_test.go b/error_test.go
@@ -177,6 +177,23 @@ func TestErrorPrettyPrint(t *testing.T) {
 			source:   "aaa\nbbb\nccc",
 			expected: "filename.txt:2:6: error at out of source [kind]",
 		},
+		{
+			message: "error at zero column",
+			line:    1,
+			column:  0,
+			source:  "this is source",
+			expected: `filename.txt:1:0: error at zero column [kind]
+  |
+1 | this is source
+  | `,
+		},
+		{
+			message:  "error at zero line and zero column",
+			line:     0,
+			column:   0,
+			source:   "this is source",
+			expected: `filename.txt:0:0: error at zero line and zero column [kind]`,
+		},
 	}
 
 	for _, tc := range testCases {
diff --git a/testdata/examples/broken_yaml.out b/testdata/examples/broken_yaml.out
@@ -1 +1 @@
-test.yaml:0:0: could not parse as YAML: yaml: line 6: mapping values are not allowed in this context [yaml-syntax]
+test.yaml:6:0: could not parse as YAML: yaml: line 6: mapping values are not allowed in this context [yaml-syntax]

Original file line number	Diff line number	Diff line change
`@@ -1 +1 @@`
`1`		`-test.yaml:0:0: could not parse as YAML: yaml: line 6: mapping values are not allowed in this context [yaml-syntax]`
	`1`	`+test.yaml:6:0: could not parse as YAML: yaml: line 6: mapping values are not allowed in this context [yaml-syntax]`