[pkg/ottl] Add OTTL context inferrer utility

.chloggen/ottl-add-context-inferrer-utility.yaml

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+# 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: Add OTTL context inferrer utility to resolve statements context based on its paths
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [29017]
+
+# (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: |
+  The `ottl` package has a new interface `ottl.ContextInferrer`, and two new functions to create a priority-based 
+  context inferrer `ottl.NewPriorityContextInferrer` and `ottl.DefaultPriorityContextInferrer`. 
+
+# 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: [api]

pkg/ottl/context_inferrer.go

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+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package ottl // import "github.com/open-telemetry/opentelemetry-collector-contrib/pkg/ottl"
+
+import "math"
+
+var (
+	defaultContextInferPriority = []string{
+		"log",
+		"metric",
+		"datapoint",
+		"spanevent",
+		"span",
+		"resource",
+		"scope",
+		"instrumentation_scope",
+	}
+)
+
+// contextInferrer is an interface used to infer the OTTL context from statements paths.
+type contextInferrer interface {
+	// infer returns the OTTL context inferred from the given statements paths.
+	infer(statements []string) (string, error)
+}
+
+type priorityContextInferrer struct {
+	contextPriority map[string]int
+}
+
+func (s *priorityContextInferrer) infer(statements []string) (string, error) {
+	var inferredContext string
+	var inferredContextPriority int
+
+	for _, statement := range statements {
+		parsed, err := parseStatement(statement)
+		if err != nil {
+			return inferredContext, err
+		}
+
+		for _, p := range getParsedStatementPaths(parsed) {
+			pathContextPriority, ok := s.contextPriority[p.Context]
+			if !ok {
+				// Lowest priority
+				pathContextPriority = math.MaxInt
+			}
+
+			if inferredContext == "" || pathContextPriority < inferredContextPriority {
+				inferredContext = p.Context
+				inferredContextPriority = pathContextPriority
+			}
+		}
+	}
+
+	return inferredContext, nil
+}
+
+// defaultPriorityContextInferrer is like newPriorityContextInferrer, but using the default
+// context priorities and ignoring unknown/non-prioritized contexts.
+func defaultPriorityContextInferrer() contextInferrer {
+	return newPriorityContextInferrer(defaultContextInferPriority)
+}
+
+// newPriorityContextInferrer creates a new priority-based context inferrer.
+// To infer the context, it compares all [ottl.Path.Context] values, prioritizing them based
+// on the provide contextsPriority argument, the lower the context position is in the array,
+// the more priority it will have over other items.
+// If unknown/non-prioritized contexts are found on the statements, they can be either ignored
+// or considered when no other prioritized context is found. To skip unknown contexts, the
+// ignoreUnknownContext argument must be set to false.
+func newPriorityContextInferrer(contextsPriority []string) contextInferrer {
+	contextPriority := make(map[string]int, len(contextsPriority))
+	for i, ctx := range contextsPriority {
+		contextPriority[ctx] = i
+	}
+	return &priorityContextInferrer{
+		contextPriority: contextPriority,
+	}
+}

pkg/ottl/context_inferrer_test.go

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+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package ottl
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func Test_NewPriorityContextInferrer_Infer(t *testing.T) {
+	tests := []struct {
+		name       string
+		priority   []string
+		statements []string
+		expected   string
+	}{
+		{
+			name:       "with priority and contexts",
+			priority:   []string{"spanevent", "span", "resource"},
+			statements: []string{"set(span.foo, resource.value) where spanevent.bar == true"},
+			expected:   "spanevent",
+		},
+		{
+			name:     "with multiple statements",
+			priority: []string{"spanevent", "span", "resource"},
+			statements: []string{
+				"set(resource.foo, resource.value) where span.bar == true",
+				"set(resource.foo, resource.value) where spanevent.bar == true",
+			},
+			expected: "spanevent",
+		},
+		{
+			name:       "with no context",
+			priority:   []string{"log", "resource"},
+			statements: []string{"set(foo, true) where bar == true"},
+			expected:   "",
+		},
+		{
+			name:       "with empty priority",
+			statements: []string{"set(foo.name, true) where bar.name == true"},
+			expected:   "foo",
+		},
+		{
+			name:       "with unknown context",
+			priority:   []string{"foo", "bar"},
+			statements: []string{"set(span.foo, true) where span.bar == true"},
+			expected:   "span",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			inferrer := newPriorityContextInferrer(tt.priority)
+			inferredContext, err := inferrer.infer(tt.statements)
+			require.NoError(t, err)
+			assert.Equal(t, tt.expected, inferredContext)
+		})
+	}
+}
+
+func Test_NewPriorityContextInferrer_InvalidStatement(t *testing.T) {
+	inferrer := newPriorityContextInferrer([]string{"foo"})
+	statements := []string{"set(foo.field,"}
+	_, err := inferrer.infer(statements)
+	require.ErrorContains(t, err, "unexpected token")
+}
+
+func Test_DefaultPriorityContextInferrer(t *testing.T) {
+	expectedPriority := []string{
+		"log",
+		"metric",
+		"datapoint",
+		"spanevent",
+		"span",
+		"resource",
+		"scope",
+		"instrumentation_scope",
+	}
+
+	inferrer := defaultPriorityContextInferrer().(*priorityContextInferrer)
+	require.NotNil(t, inferrer)
+
+	for pri, ctx := range expectedPriority {
+		require.Equal(t, pri, inferrer.contextPriority[ctx])
+	}
+}