Merge #15177: rest: Improve tests and documention of /headers and /block

7cf994d qa: Improve tests of /rest/headers and /rest/block (João Barbosa)
0825b86 doc: /rest/block responds with 404 if block does not exist (João Barbosa)
be625f7 doc: Explain empty result of /rest/headers (João Barbosa)

Pull request description:

  Follow up of #15107.

Tree-SHA512: a7fdeed05216e3eda9604664db529237c2d0ddf422cfac139d6345a22b6e00bfe870d4e3f177423db7d4efb295ac2dc0ca2eb20c9c27c0719b89fd5428860d03

Author: laanwj

doc/REST-interface.md

@@ -27,6 +27,7 @@ For full TX query capability, one must enable the transaction index via "txindex
 `GET /rest/block/notxdetails/<BLOCK-HASH>.<bin|hex|json>`
 
 Given a block hash: returns a block, in binary, hex-encoded binary or JSON formats.
+Responds with 404 if the block doesn't exist.
 
 The HTTP request and response are both handled entirely in-memory, thus making maximum memory usage at least 2.66MB (1 MB max block, plus hex encoding) per request.
 
@@ -36,6 +37,7 @@ With the /notxdetails/ option JSON response will only contain the transaction ha
 `GET /rest/headers/<COUNT>/<BLOCK-HASH>.<bin|hex|json>`
 
 Given a block hash: returns <COUNT> amount of blockheaders in upward direction.
+Returns empty if the block doesn't exist or it isn't in the active chain.
 
 #### Chaininfos
 `GET /rest/chaininfo.json`

test/functional/interface_rest.py

@@ -201,6 +201,16 @@ def run_test(self):
         self.log.info("Test the /block and /headers URIs")
         bb_hash = self.nodes[0].getbestblockhash()
 
+        # Check result if block does not exists
+        assert_equal(self.test_rest_request('/headers/1/0000000000000000000000000000000000000000000000000000000000000000'), [])
+        self.test_rest_request('/block/0000000000000000000000000000000000000000000000000000000000000000', status=404, ret_type=RetType.OBJ)
+
+        # Check result if block is not in the active chain
+        self.nodes[0].invalidateblock(bb_hash)
+        assert_equal(self.test_rest_request('/headers/1/{}'.format(bb_hash)), [])
+        self.test_rest_request('/block/{}'.format(bb_hash))
+        self.nodes[0].reconsiderblock(bb_hash)
+
         # Check binary format
         response = self.test_rest_request("/block/{}".format(bb_hash), req_type=ReqType.BIN, ret_type=RetType.OBJ)
         assert_greater_than(int(response.getheader('content-length')), 80)