feat(CodeChunk): Add executeAuto and executePure properties

schema/CodeChunk.schema.yaml

@@ -20,6 +20,26 @@ properties:
         items:
           $ref: BlockContent
       - type: string
+  executeAuto:
+    '@id': stencila:executeAuto
+    description: Under which circumstances the node should be automatically executed.
+    enum:
+      - Never
+      - Needed
+      - Always
+    default: Needed
+    $comment: |
+      `Never`: Never automatically execute the code chunk. Only execute when the user explicitly runs
+      the code (or its containing document).
+      `Needed`: Automatically execute the code chunk if needed. Execute the code chunk if it is an 
+      upstream dependency of a node that has been executed, or is a downstream dependent of a node that
+      has been executed.
+      `Always`: Always execute the code, even if it, or its dependencies, are unchanged since the 
+      last time it was executed.
+  executePure:
+    '@id': stencila:executePure
+    description: Whether the code should be treated as side-effect free when executed.
+    type: boolean
   outputs:
     '@id': stencila:outputs
     description: Outputs from executing the chunk.

schema/CodeExecutable.schema.yaml

@@ -63,7 +63,7 @@ properties:
       last executed.
   executeStatus:
     '@id': stencila:executeStatus
-    description: Status of the most recent, including in progress, execution of the code.
+    description: Status of the most recent, including any current, execution of the code.
     enum:
       - Scheduled
       - ScheduledPreviouslyFailed

schema/CodeExpression.schema.yaml

@@ -11,3 +11,7 @@ properties:
     description: The value of the expression when it was last evaluated.
     allOf:
       - $ref: Node
+$comment:
+  Note that `CodeExpression` nodes lack the `executeAuto` and `executePure` properties that
+  `CodeChunk` nodes have because they will always be executed (when dependencies) change and
+  should be side-effect free.

ts/bindings/rust.ts

@@ -83,6 +83,7 @@ const noBoxTypes = [
   'ClaimClaimType',
   'CodeExecutableExecuteRequired',
   'CodeExecutableExecuteStatus',
+  'CodeChunkExecuteAuto',
   'ListOrder',
   'NoteNoteType',
   'SoftwareSessionStatus',