Introduce FileRules Refaster rule collection (#767)

error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/FileRules.java

@@ -0,0 +1,43 @@
+package tech.picnic.errorprone.refasterrules;
+
+import static java.nio.charset.StandardCharsets.UTF_8;
+
+import com.google.errorprone.refaster.annotation.AfterTemplate;
+import com.google.errorprone.refaster.annotation.BeforeTemplate;
+import java.io.IOException;
+import java.nio.charset.Charset;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
+
+/** Refaster rules related to expressions dealing with files. */
+@OnlineDocumentation
+final class FileRules {
+  private FileRules() {}
+
+  /** Prefer {@link Files#readString(Path, Charset)} over more contrived alternatives. */
+  static final class FilesReadStringWithCharset {
+    @BeforeTemplate
+    String before(Path path, Charset charset) throws IOException {
+      return new String(Files.readAllBytes(path), charset);
+    }
+
+    @AfterTemplate
+    String after(Path path, Charset charset) throws IOException {
+      return Files.readString(path, charset);
+    }
+  }
+
+  /** Prefer {@link Files#readString(Path)} over more verbose alternatives. */
+  static final class FilesReadString {
+    @BeforeTemplate
+    String before(Path path) throws IOException {
+      return Files.readString(path, UTF_8);
+    }
+
+    @AfterTemplate
+    String after(Path path) throws IOException {
+      return Files.readString(path);
+    }
+  }
+}

error-prone-contrib/src/test/java/tech/picnic/errorprone/refasterrules/RefasterRulesTest.java

@@ -40,6 +40,7 @@ final class RefasterRulesTest {
           ComparatorRules.class,
           DoubleStreamRules.class,
           EqualityRules.class,
+          FileRules.class,
           ImmutableListRules.class,
           ImmutableListMultimapRules.class,
           ImmutableMapRules.class,

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/FileRulesTestInput.java

@@ -0,0 +1,17 @@
+package tech.picnic.errorprone.refasterrules;
+
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;
+
+final class FileRulesTest implements RefasterRuleCollectionTestCase {
+  String testFilesReadStringWithCharset() throws IOException {
+    return new String(Files.readAllBytes(Paths.get("foo")), StandardCharsets.ISO_8859_1);
+  }
+
+  String testFilesReadString() throws IOException {
+    return Files.readString(Paths.get("foo"), StandardCharsets.UTF_8);
+  }
+}

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/FileRulesTestOutput.java

@@ -0,0 +1,17 @@
+package tech.picnic.errorprone.refasterrules;
+
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Paths;
+import tech.picnic.errorprone.refaster.test.RefasterRuleCollectionTestCase;
+
+final class FileRulesTest implements RefasterRuleCollectionTestCase {
+  String testFilesReadStringWithCharset() throws IOException {
+    return Files.readString(Paths.get("foo"), StandardCharsets.ISO_8859_1);
+  }
+
+  String testFilesReadString() throws IOException {
+    return Files.readString(Paths.get("foo"));
+  }
+}