docs(staking): add cancel-unbond delegations spec

x/staking/spec/02_state_transitions.md

@@ -91,6 +91,12 @@ Delegation may be called.
   shares from the `BondedPool` to the `NotBondedPool` `ModuleAccount`
 * remove the validator if it is unbonded and there are no more delegation shares.
 
+### Cancel an `UnbondingDelegation` Entry 
+When a `cancel unbond delegation` occures both the `validator` and the `delegation` and an `UnbondingDelegationQueue` state will be affected
+* if cancel unbonding delegation amount equals to an `UnbondingDelegation` Entry `balance` then an `UnbondingDelegation` Entry deleted from `UnbondingDelegationQueue`.
+* if cancel unbonding delegation amount is less then an `UnbondingDelegation` Entry balance then an `UnbondingDelegation` Entry updated with new balance to the `UnbondingDelegationQueue`. 
+* cancel `amount` is [Delegated](02_state_transitions.md#delegations) back to previous `validator` 
+
 ### Complete Unbonding
 
 For undelegations which do not complete immediately, the following operations

x/staking/spec/03_messages.md

@@ -116,6 +116,27 @@ When this message is processed the following actions occur:
 
 ![Unbond sequence](../../../docs/uml/svg/unbond_sequence.svg)
 
+## MsgCancelUnbondingDelegation
+The `MsgCancelUnbondingDelegation` message allows delegators to cancel the `unbondingDelegation` entry and re-deleagate back to previous validator.
+
++++ https://github.com/cosmos/cosmos-sdk/blob/28243eb41c16ecfc95631ac2bb266dd28ed5c317/proto/cosmos/staking/v1beta1/tx.proto#L36-L38
+
++++ https://github.com/cosmos/cosmos-sdk/blob/28243eb41c16ecfc95631ac2bb266dd28ed5c317/proto/cosmos/staking/v1beta1/tx.proto#L144-L154
+
++++ https://github.com/cosmos/cosmos-sdk/blob/28243eb41c16ecfc95631ac2bb266dd28ed5c317/proto/cosmos/staking/v1beta1/tx.proto#L156-L157
+
+
+This message is expected to fail if:
+* if an `unbondingDelegation` entry is already processed
+* if cancel unbonding delegation amount is greater than the `unbondingDelegation` entry balance
+* if cancel unbonding delegation height is not exists in the `unbondingDelegationQueue` of the delegator
+
+When this message is processed the following actions occur:
+* if delegator `unbondingDelegation` entry is not processed
+* if cancel `unbondingDelegation` amount is less than or equal to the `unbondingDelegation` entry of delegator 
+* if cancel unbonding delegation height is exists in the `unbondingDelegation` queue of the delegator
+
+
 ## MsgBeginRedelegate
 
 The redelegation command allows delegators to instantly switch validators. Once

x/staking/spec/07_events.md

@@ -63,6 +63,18 @@ The staking module emits the following events:
 
 * [0] Time is formatted in the RFC3339 standard
 
+### MsgCancelUnbondingDelegation
+
+| Type                          | Attribute Key       | Attribute Value                     |
+| ----------------------------- | ------------------  | ------------------------------------|
+| cancel_unbonding_delegation   | validator           | {validatorAddress}                  |
+| cancel_unbonding_delegation   | delegator           | {delegatorAddress}                  |
+| cancel_unbonding_delegation   | amount              | {cancelUnbondingDelegationAmount}   |
+| cancel_unbonding_delegation   | creation_height     | {unbondingCreationHeight}           |
+| message                       | module              | staking                             |
+| message                       | action              | cancel_unbond                       |
+| message                       | sender              | {senderAddress}                     |
+
 ### MsgBeginRedelegate
 
 | Type       | Attribute Key         | Attribute Value       |

x/staking/spec/09_client.md

@@ -712,6 +712,19 @@ Example:
 ```bash
 simd tx staking unbond cosmosvaloper1gghjut3ccd8ay0zduzj64hwre2fxs9ldmqhffj 100stake --from mykey
 ```
+#### cancel unbond 
+The command `cancel-unbond` allow users to cancel unbonding delegation entry and re-delegate back to previous validator.
+
+Usage:
+```bash
+simd tx staking cancel-unbond [validator-addr] [amount] [creation-height]
+```
+
+Example:
+```bash
+simd tx staking cancel-unbond cosmosvaloper1gghjut3ccd8ay0zduzj64hwre2fxs9ldmqhffj 100stake 123123 --from mykey
+```
+
 
 ## gRPC
 

x/staking/spec/README.md

@@ -42,6 +42,7 @@ network.
     * [MsgEditValidator](03_messages.md#msgeditvalidator)
     * [MsgDelegate](03_messages.md#msgdelegate)
     * [MsgUndelegate](03_messages.md#msgundelegate)
+    * [MsgCancelUnbondingDelegation](03_messages.md#msgcancelunbondingdelegation)
     * [MsgBeginRedelegate](03_messages.md#msgbeginredelegate)
 4. **[Begin-Block](04_begin_block.md)**
     * [Historical Info Tracking](04_begin_block.md#historical-info-tracking)