Crash early if any interceptor is null. (square#3555)

Closes: square#3514

Author: swankjesse

okhttp-tests/src/test/java/okhttp3/OkHttpClientTest.java

@@ -127,4 +127,46 @@ public final class OkHttpClientTest {
     OkHttpClient clientB = TestUtil.defaultClient();
     assertEquals(clientA.certificatePinner(), clientB.certificatePinner());
   }
+
+  @Test public void nullInterceptor() {
+    OkHttpClient.Builder builder = new OkHttpClient.Builder();
+    try {
+      builder.addInterceptor(null);
+      fail();
+    } catch (IllegalArgumentException expected) {
+      assertEquals("interceptor == null", expected.getMessage());
+    }
+  }
+
+  @Test public void nullNetworkInterceptor() {
+    OkHttpClient.Builder builder = new OkHttpClient.Builder();
+    try {
+      builder.addNetworkInterceptor(null);
+      fail();
+    } catch (IllegalArgumentException expected) {
+      assertEquals("interceptor == null", expected.getMessage());
+    }
+  }
+
+  @Test public void nullInterceptorInList() {
+    OkHttpClient.Builder builder = new OkHttpClient.Builder();
+    builder.interceptors().add(null);
+    try {
+      builder.build();
+      fail();
+    } catch (IllegalStateException expected) {
+      assertEquals("Null interceptor: [null]", expected.getMessage());
+    }
+  }
+
+  @Test public void nullNetworkInterceptorInList() {
+    OkHttpClient.Builder builder = new OkHttpClient.Builder();
+    builder.networkInterceptors().add(null);
+    try {
+      builder.build();
+      fail();
+    } catch (IllegalStateException expected) {
+      assertEquals("Null network interceptor: [null]", expected.getMessage());
+    }
+  }
 }

okhttp/src/main/java/okhttp3/CertificatePinner.java

@@ -226,7 +226,8 @@ List<Pin> findMatchingPins(String hostname) {
   }
 
   /** Returns a certificate pinner that uses {@code certificateChainCleaner}. */
-  CertificatePinner withCertificateChainCleaner(CertificateChainCleaner certificateChainCleaner) {
+  CertificatePinner withCertificateChainCleaner(
+      @Nullable CertificateChainCleaner certificateChainCleaner) {
     return equal(this.certificateChainCleaner, certificateChainCleaner)
         ? this
         : new CertificatePinner(pins, certificateChainCleaner);

okhttp/src/main/java/okhttp3/OkHttpClient.java

@@ -268,6 +268,13 @@ public OkHttpClient() {
     this.readTimeout = builder.readTimeout;
     this.writeTimeout = builder.writeTimeout;
     this.pingInterval = builder.pingInterval;
+
+    if (interceptors.contains(null)) {
+      throw new IllegalStateException("Null interceptor: " + interceptors);
+    }
+    if (networkInterceptors.contains(null)) {
+      throw new IllegalStateException("Null network interceptor: " + networkInterceptors);
+    }
   }
 
   private X509TrustManager systemDefaultTrustManager() {
@@ -862,6 +869,7 @@ public List<Interceptor> interceptors() {
     }
 
     public Builder addInterceptor(Interceptor interceptor) {
+      if (interceptor == null) throw new IllegalArgumentException("interceptor == null");
       interceptors.add(interceptor);
       return this;
     }
@@ -876,6 +884,7 @@ public List<Interceptor> networkInterceptors() {
     }
 
     public Builder addNetworkInterceptor(Interceptor interceptor) {
+      if (interceptor == null) throw new IllegalArgumentException("interceptor == null");
       networkInterceptors.add(interceptor);
       return this;
     }