CredentialOptions#jsonCredentials(InputStream) requires the InputStream to be open until it's used in BigtableSession

[udoprog]

When setting up credentials with CredentialOptions#jsonCredentials(InputStream) I was suprised to see that the resulting CredentialOptions require the InputStream to be open.

My code uses an abstraction to setup CredentialOptions instances. The class itself does not expose any statefullness (i.e. isReadable(), close()) meaning there's no reasonable way for a user of an CredentialOptions instance to check if it's readable or not.

I'd prefer if CredentialOptions.jsonCredentials(InputStream) fully read and parsed the given InputStream, and stored the credentials in memory, this would allow for patterns like the following to safely work without leaking an open InputStream.

public CredentialOptions buildCredentials() throws IOException {
    try (final InputStream in = Files.newInputStream(...)) {
        return CredentialOptions.jsonCredentials(in);
    }
}

The kind of exceptions you'll see otherwise are the following:

java.nio.channels.ClosedChannelException
        at sun.nio.ch.FileChannelImpl.ensureOpen(FileChannelImpl.java:110)
        at sun.nio.ch.FileChannelImpl.read(FileChannelImpl.java:147)
        at sun.nio.ch.ChannelInputStream.read(ChannelInputStream.java:65)
        at sun.nio.ch.ChannelInputStream.read(ChannelInputStream.java:109)
        at sun.nio.ch.ChannelInputStream.read(ChannelInputStream.java:103)
        at com.fasterxml.jackson.core.json.ByteSourceJsonBootstrapper.ensureLoaded(ByteSourceJsonBootstrapper.java:489)
        at com.fasterxml.jackson.core.json.ByteSourceJsonBootstrapper.detectEncoding(ByteSourceJsonBootstrapper.java:126)
        at com.fasterxml.jackson.core.json.ByteSourceJsonBootstrapper.constructParser(ByteSourceJsonBootstrapper.java:215)
        at com.fasterxml.jackson.core.JsonFactory._createParser(JsonFactory.java:1240)
        at com.fasterxml.jackson.core.JsonFactory.createParser(JsonFactory.java:802)
        at com.fasterxml.jackson.core.JsonFactory.createJsonParser(JsonFactory.java:972)
        at com.google.api.client.json.jackson2.JacksonFactory.createJsonParser(JacksonFactory.java:93)
        at com.google.api.client.json.JsonObjectParser.parseAndClose(JsonObjectParser.java:85)
        at com.google.api.client.json.JsonObjectParser.parseAndClose(JsonObjectParser.java:81)
        at com.google.auth.oauth2.GoogleCredentials.fromStream(GoogleCredentials.java:101)
        at com.google.cloud.bigtable.config.CredentialFactory.getInputStreamCredential(CredentialFactory.java:182)
        at com.google.cloud.bigtable.config.CredentialFactory.getCredentials(CredentialFactory.java:108)
        at com.google.cloud.bigtable.grpc.BigtableSession$4.call(BigtableSession.java:249)
        at com.google.cloud.bigtable.grpc.BigtableSession$4.call(BigtableSession.java:246)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
        at java.lang.Thread.run(Thread.java:745)