Allow passing a TermBuilder to be transacted by InProgress; add TermBuilder::is_empty. r=emily

src/conn.rs

@@ -83,6 +83,7 @@ use uuid::Uuid;
 use entity_builder::{
     BuildTerms,
     InProgressBuilder,
+    TermBuilder,
 };
 
 use errors::*;
@@ -390,6 +391,15 @@ impl<'a, 'c> InProgress<'a, 'c> {
         self.use_caching = yesno;
     }
 
+    /// If you only have a reference to an `InProgress`, you can't use the easy builder.
+    /// This exists so you can make your own.
+    pub fn transact_builder(&mut self, builder: TermBuilder) -> Result<TxReport> {
+        builder.build()
+               .and_then(|(terms, tempid_set)| {
+                    self.transact_terms(terms, tempid_set)
+               })
+    }
+
     pub fn transact_terms<I>(&mut self, terms: I, tempid_set: InternSet<TempId>) -> Result<TxReport> where I: IntoIterator<Item=TermWithTempIds> {
         let w = InProgressTransactWatcher::new(
                 &mut self.tx_observer_watcher,

src/entity_builder.rs

@@ -161,6 +161,10 @@ impl TermBuilder {
         }
     }
 
+    pub fn is_empty(&self) -> bool {
+        self.terms.is_empty()
+    }
+
     #[allow(dead_code)]
     pub fn numbered_tempid(&mut self, id: i64) -> TempIdHandle {
         self.tempids.intern(TempId::Internal(id))
@@ -213,15 +217,11 @@ impl<'a, 'c> InProgressBuilder<'a, 'c> {
     /// step fails, roll back. Return the `TxReport`.
     pub fn commit(self) -> Result<TxReport> {
         let mut in_progress = self.in_progress;
-        self.builder
-            .build()
-            .and_then(|(terms, tempid_set)| {
-                in_progress.transact_terms(terms, tempid_set)
+        in_progress.transact_builder(self.builder)
                    .and_then(|report| {
                         in_progress.commit()?;
                         Ok(report)
                    })
-            })
     }
 }