Improve testability of the EnvVarHeaders struct and covered with tests.

Author: BennettSmith

Sources/Exporters/OpenTelemetryProtocol/common/EnvVarHeaders.swift

@@ -8,18 +8,37 @@ import OpenTelemetryApi
 
 /// Provides a framework for detection of resource information from the environment variable
 public struct EnvVarHeaders {
-    private static let otelAttributesEnv = "OTEL_EXPORTER_OTLP_HEADERS"
     private static let labelListSplitter = Character(",")
     private static let labelKeyValueSplitter = Character("=")
 
     ///  This resource information is loaded from the 
     ///  environment variable.
-    public static let attributes : [(String,String)]? = parseAttributes(rawEnvAttributes: ProcessInfo.processInfo.environment[otelAttributesEnv])
+    public static let attributes : [(String,String)]? = EnvVarHeaders.attributes()
+
+    public static func attributes(for rawEnvAttributes: String? = ProcessInfo.processInfo.environment["OTEL_EXPORTER_OTLP_HEADERS"]) -> [(String,String)]? {
+        parseAttributes(rawEnvAttributes: rawEnvAttributes)
+    }
 
     private init() {}
 
+    private static func isKey(token: String) -> Bool {
+        let alpha = CharacterSet(charactersIn: "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
+        let digit = CharacterSet(charactersIn: "0123456789")
+        let special = CharacterSet(charactersIn: "!#$%&'*+-.^_`|~")
+        let tchar = special.union(alpha).union(digit)
+        return tchar.isSuperset(of: CharacterSet(charactersIn: token))
+    }
+
+    private static func isValue(baggage: String) -> Bool {
+        let asciiSet = CharacterSet(charactersIn: UnicodeScalar(0) ..< UnicodeScalar(0x80))
+        let special = CharacterSet(charactersIn: "^\"|\"$")
+        let baggageOctet = asciiSet.subtracting(.controlCharacters).subtracting(.whitespaces).union(special)
+        return baggageOctet.isSuperset(of: CharacterSet(charactersIn: baggage))
+    }
+
     /// Creates a label map from the environment variable string.
     /// - Parameter rawEnvLabels: the comma-separated list of labels
+    /// NOTE: Parsing does not fully match W3C Correlation-Context
     private static func parseAttributes(rawEnvAttributes: String?) -> [(String, String)]? {
         guard let rawEnvLabels = rawEnvAttributes else { return nil }
 
@@ -30,10 +49,17 @@ public struct EnvVarHeaders {
             if split.count != 2 {
                 return
             }
+
             let key = split[0].trimmingCharacters(in: .whitespaces)
-            let value = split[1].trimmingCharacters(in: CharacterSet(charactersIn: "^\"|\"$"))
+            guard isKey(token: key) else { return }
+
+            let value = split[1].trimmingCharacters(in: .whitespaces)
+            guard isValue(baggage: value) else { return }
+
             labels.append((key,value))
         }
-        return labels
+        return labels.count > 0 ? labels : nil
     }
 }
+
+

Tests/ExportersTests/OpenTelemetryProtocol/EnvVarHeadersTests.swift

@@ -0,0 +1,50 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import Foundation
+import OpenTelemetryProtocolExporter
+import XCTest
+
+class EnvVarHeadersTests: XCTestCase {
+
+    func test_attributesIsNil_whenAccessedThroughStaticProperty() throws {
+        XCTAssertNil(EnvVarHeaders.attributes)
+    }
+
+    func test_attributesIsNil_whenNoRawValueProvided() throws {
+        XCTAssertNil(EnvVarHeaders.attributes(for: nil))
+    }
+
+    func test_attributesContainOneKeyValuePair_whenRawValueProvidedHasOneKeyValuePair() throws {
+        let capturedAttributes = EnvVarHeaders.attributes(for: "key1=value1")
+        XCTAssertNotNil(capturedAttributes)
+        XCTAssertEqual(capturedAttributes![0].0, "key1")
+        XCTAssertEqual(capturedAttributes![0].1, "value1")
+    }
+
+    func test_attributesIsNil_whenInvalidRawValueProvided() throws {
+        XCTAssertNil(EnvVarHeaders.attributes(for: "key1"))
+    }
+
+    func test_attributesContainTwoKeyValuePair_whenRawValueProvidedHasTwoKeyValuePair() throws {
+        let capturedAttributes = EnvVarHeaders.attributes(for: " key1=value1,  key2 = value2 ")
+        XCTAssertNotNil(capturedAttributes)
+        XCTAssertEqual(capturedAttributes![0].0, "key1")
+        XCTAssertEqual(capturedAttributes![0].1, "value1")
+        XCTAssertEqual(capturedAttributes![1].0, "key2")
+        XCTAssertEqual(capturedAttributes![1].1, "value2")
+    }
+
+    func test_attributesIsNil_whenRawValueContainsWhiteSpace() throws {
+        let capturedAttributes = EnvVarHeaders.attributes(for: "key=value with\twhitespace")
+        XCTAssertNil(capturedAttributes)
+    }
+
+    func test_attributesExcludesInvalidTuples_whenRawValueContainsInvalidCharacters() throws {
+        let capturedAttributes = EnvVarHeaders.attributes(for: "key=value with whitespace")
+        XCTAssertNil(capturedAttributes)
+    }
+
+}