Let JsonValueReader.nextString read numbers. (#390)

* Let JsonValueReader.nextString read numbers.

This adds parity with JsonUtf8Reader and lets big number literals in JSON be read in as strings in Java.

* Remove trailing 0 in float literal.

moshi/src/main/java/com/squareup/moshi/JsonValueReader.java

@@ -152,9 +152,19 @@ final class JsonValueReader extends JsonReader {
   }
 
   @Override public String nextString() throws IOException {
-    String peeked = require(String.class, Token.STRING);
+    Object peeked = (stackSize != 0 ? stack[stackSize - 1] : null);
+    if (peeked instanceof String) {
       remove();
-    return peeked;
+      return (String) peeked;
+    }
+    if (peeked instanceof Number) {
+      remove();
+      return peeked.toString();
+    }
+    if (peeked == JSON_READER_CLOSED) {
+      throw new IllegalStateException("JsonReader is closed");
+    }
+    throw typeMismatch(peeked, Token.STRING);
   }
 
   @Override public int selectString(Options options) throws IOException {

moshi/src/test/java/com/squareup/moshi/JsonUtf8ReaderTest.java

@@ -336,6 +336,18 @@ public final class JsonUtf8ReaderTest {
     assertEquals("-0", reader.nextString());
   }
 
+  @Test public void numberToStringCoersion() throws Exception {
+    JsonReader reader = newReader("[0, 9223372036854775807, 2.5, 3.010, \"a\", \"5\"]");
+    reader.beginArray();
+    assertThat(reader.nextString()).isEqualTo("0");
+    assertThat(reader.nextString()).isEqualTo("9223372036854775807");
+    assertThat(reader.nextString()).isEqualTo("2.5");
+    assertThat(reader.nextString()).isEqualTo("3.010");
+    assertThat(reader.nextString()).isEqualTo("a");
+    assertThat(reader.nextString()).isEqualTo("5");
+    reader.endArray();
+  }
+
   @Test public void quotedNumberWithEscape() throws IOException {
     JsonReader reader = newReader("[\"12\u00334\"]");
     reader.setLenient(true);

moshi/src/test/java/com/squareup/moshi/JsonValueReaderTest.java

@@ -17,6 +17,7 @@ package com.squareup.moshi;
 
 import java.io.IOException;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
@@ -423,6 +424,19 @@ public final class JsonValueReaderTest {
     }
   }
 
+  @Test public void numberToStringCoersion() throws Exception {
+    JsonReader reader =
+        new JsonValueReader(Arrays.asList(0, 9223372036854775807L, 2.5d, 3.01f, "a", "5"));
+    reader.beginArray();
+    assertThat(reader.nextString()).isEqualTo("0");
+    assertThat(reader.nextString()).isEqualTo("9223372036854775807");
+    assertThat(reader.nextString()).isEqualTo("2.5");
+    assertThat(reader.nextString()).isEqualTo("3.01");
+    assertThat(reader.nextString()).isEqualTo("a");
+    assertThat(reader.nextString()).isEqualTo("5");
+    reader.endArray();
+  }
+
   @Test public void tooDeeplyNestedArrays() throws IOException {
     Object root = Collections.emptyList();
     for (int i = 0; i < 32; i++) {