[pkg/ottl] Refactor grammar validation to use the AST visitor and combining errors (#35728)

Co-authored-by: Evan Bradley <[email protected]>
Co-authored-by: Tyler Helmuth <[email protected]>

Author: 3 people

.chloggen/ottl-grammar-custom-errors-visitor.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: pkg/ottl
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: "Parsing invalid statements and conditions now prints all errors instead of just the first one found."
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [35728]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [user]

pkg/ottl/functions.go

@@ -33,16 +33,7 @@ func buildOriginalText(path *path) string {
 	for i, f := range path.Fields {
 		builder.WriteString(f.Name)
 		if len(f.Keys) > 0 {
-			for _, k := range f.Keys {
-				builder.WriteString("[")
-				if k.Int != nil {
-					builder.WriteString(strconv.FormatInt(*k.Int, 10))
-				}
-				if k.String != nil {
-					builder.WriteString(*k.String)
-				}
-				builder.WriteString("]")
-			}
+			builder.WriteString(buildOriginalKeysText(f.Keys))
 		}
 		if i != len(path.Fields)-1 {
 			builder.WriteString(".")
@@ -51,6 +42,23 @@ func buildOriginalText(path *path) string {
 	return builder.String()
 }
 
+func buildOriginalKeysText(keys []key) string {
+	var builder strings.Builder
+	if len(keys) > 0 {
+		for _, k := range keys {
+			builder.WriteString("[")
+			if k.Int != nil {
+				builder.WriteString(strconv.FormatInt(*k.Int, 10))
+			}
+			if k.String != nil {
+				builder.WriteString(*k.String)
+			}
+			builder.WriteString("]")
+		}
+	}
+	return builder.String()
+}
+
 func (p *Parser[K]) newPath(path *path) (*basePath[K], error) {
 	if len(path.Fields) == 0 {
 		return nil, fmt.Errorf("cannot make a path from zero fields")