Run and Fix CacheTest emulating windows

[yschimke]

Investigate and fix issues affecting windows.
From #9335

[yschimke]

The fix isn't trivial. cc @swankjesse

We get here

        // Update the cache after combining headers but before stripping the
        // Content-Encoding header (as performed by initContentStream()).
        cache!!.trackConditionalCacheHit()
        cache.update(cacheResponse, response)

or more precisely

  internal fun update(
    cached: Response,
    network: Response,
  ) {
    val entry = Entry(network)
    val snapshot = (cached.body as CacheResponseBody).snapshot <-- we are still planning to use the cache response body
    var editor: DiskLruCache.Editor? = null
    try {
      editor = snapshot.edit() ?: return // edit() returns null if snapshot is not current.
      entry.writeTo(editor)
      editor.commit()
    } catch (_: IOException) {
      abortQuietly(editor)
    }
  }

we got the cache response body from, so lockingSourceCount is > 0

    private fun newSource(index: Int): Source {
      val fileSource = fileSystem.source(cleanFiles[index])
      if (civilizedFileSystem) return fileSource

      lockingSourceCount++
      return object : ForwardingSource(fileSource) {
        private var closed = false

        override fun close() {
          super.close()
          if (!closed) {
            closed = true
            synchronized(this@DiskLruCache) {
              lockingSourceCount--
              if (lockingSourceCount == 0 && zombie) {
                removeEntry(this@Entry)
              }
            }
          }
        }
      }
    }

So eventually fails here

    if (entry != null && entry.lockingSourceCount != 0) {
      return null // We can't write this file because a reader is still reading it.
    }

[yschimke]

At least one of the failures makes it looks expected.

  /**
   * Each read sees a snapshot of the file at the time read was called. This means that two reads of
   * the same key can see different data.
   */
  @Test
  fun readAndWriteOverlapsMaintainConsistency() {
    Assumptions.assumeFalse(windows) // Can't edit while a read is in progress.

[Nohus]

@yschimke Hello, I was following this PR with much hope as I raised the original issue. Why was it closed?

[yschimke]

I thought there was one further along, non draft. Let me check and reopen if not

[yschimke]

closing in favour of #9446