Fix Update ParseExpression to parse any json passed to it. (#418)

* Parse JSON

* Update parse.go

Co-authored-by: Kazuma Watanabe <[email protected]>

---------

Co-authored-by: Kazuma Watanabe <[email protected]>

Author: rorychatterton

hclext/parse.go

@@ -13,22 +13,27 @@ import (
 // This function specializes in parsing intermediate expressions in the file,
 // so it takes into account the hack on trailing newlines in heredoc.
 func ParseExpression(src []byte, filename string, start hcl.Pos) (hcl.Expression, hcl.Diagnostics) {
+	// Handle HCL files: .tf (Terraform HCL) and .hcl (HCL config like .tflint.hcl)
 	if strings.HasSuffix(filename, ".tf") || strings.HasSuffix(filename, ".hcl") {
 		// HACK: Always add a newline to avoid heredoc parse errors.
 		// @see https://github.com/hashicorp/hcl/issues/441
 		src = []byte(string(src) + "\n")
 		return hclsyntax.ParseExpression(src, filename, start)
 	}
 
-	if strings.HasSuffix(filename, ".tf.json") {
+	// Handle JSON files:
+	// We accept any .json file (including .tf.json), not just specific ones like .tflint.json.
+	// The calling functions are responsible for validating that the file should be processed.
+	// If the content is not valid HCL-compatible JSON, the JSON parser will return appropriate diagnostics.
+	if strings.HasSuffix(filename, ".json") {
 		return json.ParseExpressionWithStartPos(src, filename, start)
 	}
 
 	return nil, hcl.Diagnostics{
 		{
 			Severity: hcl.DiagError,
 			Summary:  "Unexpected file extension",
-			Detail:   fmt.Sprintf("The file name `%s` is a file with an unexpected extension. Valid extensions are `.tf`, `.tf.json`, and `.hcl`.", filename),
+			Detail:   fmt.Sprintf("The file name `%s` is a file with an unexpected extension. Valid extensions are `.tf`, `.tf.json`, `.hcl`, and `.json`.", filename),
 		},
 	}
 }

hclext/parse_test.go

@@ -30,10 +30,18 @@ func TestParseExpression(t *testing.T) {
 			DiagCount: 0,
 		},
 		{
-			Name:      "HCL but file extension is invalid (*.json)",
+			Name:      "JSON (*.json)",
 			Source:    `"baz"`,
 			Filename:  "test.json",
-			DiagCount: 1,
+			Want:      `cty.StringVal("baz")`,
+			DiagCount: 0,
+		},
+		{
+			Name:      "JSON (.tflint.json)",
+			Source:    `{"config": {"force": true}}`,
+			Filename:  ".tflint.json",
+			Want:      `cty.ObjectVal(map[string]cty.Value{"config":cty.ObjectVal(map[string]cty.Value{"force":cty.True})})`,
+			DiagCount: 0,
 		},
 		{
 			Name: "HCL heredoc with trailing newline",
@@ -61,6 +69,18 @@ EOF`,
 			Want:      `cty.ObjectVal(map[string]cty.Value{"baz":cty.NumberIntVal(1), "foo":cty.StringVal("bar")})`,
 			DiagCount: 0,
 		},
+		{
+			Name:      "Invalid JSON content",
+			Source:    `{invalid json content}`,
+			Filename:  "test.json",
+			DiagCount: 2, // JSON parser returns 2 diagnostics for this invalid JSON
+		},
+		{
+			Name:      "Invalid file extension",
+			Source:    `"test"`,
+			Filename:  "test.yaml",
+			DiagCount: 1,
+		},
 	}
 
 	for _, test := range tests {