EnvironmentVariableHelper support for boolean (#3457)

src/OpenTelemetry/Internal/EnvironmentVariableHelper.cs

@@ -111,5 +111,33 @@ namespace OpenTelemetry.Internal
 
             return true;
         }
+
+        /// <summary>
+        /// Reads an environment variable and parses it as a <see cref="bool" />.
+        /// </summary>
+        /// <param name="envVarKey">The name of the environment variable.</param>
+        /// <param name="result">The parsed value of the environment variable.</param>
+        /// <returns>
+        /// Returns <c>true</c> when a non-empty value was read; otherwise, <c>false</c>.
+        /// </returns>
+        /// <exception cref="FormatException">
+        /// Thrown when failed to parse the non-empty value.
+        /// </exception>
+        public static bool LoadBoolean(string envVarKey, out bool result)
+        {
+            result = default;
+
+            if (!LoadString(envVarKey, out string value))
+            {
+                return false;
+            }
+
+            if (!bool.TryParse(value, out result))
+            {
+                throw new FormatException($"{envVarKey} environment variable has an invalid value: '${value}'");
+            }
+
+            return true;
+        }
     }
 }

test/OpenTelemetry.Tests/Internal/EnvironmentVariableHelperTests.cs

@@ -55,6 +55,44 @@ namespace OpenTelemetry.Internal.Tests
             Assert.Null(actualValue);
         }
 
+        [Theory]
+        [InlineData("true", true)]
+        [InlineData("TRUE", true)]
+        [InlineData("false", false)]
+        [InlineData("FALSE", false)]
+        [InlineData(" true ", true)]
+        [InlineData(" false ", false)]
+        public void LoadBoolean(string value, bool expectedValue)
+        {
+            Environment.SetEnvironmentVariable(EnvVar, value);
+
+            bool actualBool = EnvironmentVariableHelper.LoadBoolean(EnvVar, out bool actualValue);
+
+            Assert.True(actualBool);
+            Assert.Equal(expectedValue, actualValue);
+        }
+
+        [Fact]
+        public void LoadBoolean_NoValue()
+        {
+            bool actualBool = EnvironmentVariableHelper.LoadBoolean(EnvVar, out bool actualValue);
+
+            Assert.False(actualBool);
+            Assert.False(actualValue);
+        }
+
+        [Theory]
+        [InlineData("something")] // non true/false
+        [InlineData(" ")] // whitespaces
+        [InlineData("0")] // 0
+        [InlineData("1")] // 1
+        public void LoadBoolean_Invalid(string value)
+        {
+            Environment.SetEnvironmentVariable(EnvVar, value);
+
+            Assert.Throws<FormatException>(() => EnvironmentVariableHelper.LoadBoolean(EnvVar, out bool _));
+        }
+
         [Theory]
         [InlineData("123", 123)]
         [InlineData("0", 0)]