Allow delete statement for tables, sets and vectors

Relates to #3472. This allow "delete tbl" as an alternative for
clear_table(tbl). Also works for vectors.

NEWS

@@ -12,6 +12,12 @@ Breaking Changes
 New Functionality
 -----------------
 
+- Support ``delete`` on tables, sets and vectors to clear their contents.
+
+	global v = vector(1, 2, 3);
+	delete v;
+	assert |v| == 0;
+
 Changed Functionality
 ---------------------
 

src/Expr.cc

@@ -408,6 +408,24 @@ NameExpr::NameExpr(IDPtr arg_id, bool const_init) : Expr(EXPR_NAME), id(std::mov
 #pragma GCC diagnostic pop
 }
 
+bool NameExpr::CanDel() const {
+    if ( IsError() )
+        return true; // avoid cascading the error report
+
+    return GetType()->Tag() == TYPE_TABLE || GetType()->Tag() == TYPE_VECTOR;
+}
+
+void NameExpr::Delete(Frame* f) {
+    if ( auto v = Eval(f) ) {
+        if ( GetType()->Tag() == TYPE_TABLE )
+            v->AsTableVal()->RemoveAll();
+        else if ( GetType()->Tag() == TYPE_VECTOR )
+            v->AsVectorVal()->Resize(0);
+        else
+            RuntimeError("delete unsupported");
+    }
+}
+
 // This isn't in-lined to avoid needing to pull in ID.h.
 const IDPtr& NameExpr::IdPtr() const { return id; }
 

src/Expr.h

@@ -428,6 +428,9 @@ class NameExpr final : public Expr {
 public:
     explicit NameExpr(IDPtr id, bool const_init = false);
 
+    bool CanDel() const override;
+    void Delete(Frame* f) override;
+
     ID* Id() const { return id.get(); }
     const IDPtr& IdPtr() const;
 

testing/btest/Baseline/language.delete-containers/.stderr

@@ -0,0 +1 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.

testing/btest/Baseline/language.delete-containers/output

@@ -0,0 +1,15 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+t, {
+[42] = 4711
+}
+s, {
+42
+}
+v, [1, 2, 3]
+t, {
+
+}
+s, {
+
+}
+v, []

testing/btest/Baseline/language.delete-table-set/.stderr

@@ -0,0 +1 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.

testing/btest/language/delete-containers.zeek

@@ -0,0 +1,24 @@
+# @TEST-DOC: Deleteing a table, set or vector removes all of its elements.
+
+# @TEST-EXEC: zeek -b %INPUT >output
+# @TEST-EXEC: btest-diff output
+# @TEST-EXEC: btest-diff .stderr
+
+global t: table[count] of count &read_expire=1sec;
+global s: set[count];
+global v = vector(1,2,3);
+
+t[42] = 4711;
+add s[42];
+
+print "t", t;
+print "s", s;
+print "v", v;
+
+delete t;
+delete s;
+delete v;
+
+print "t", t;
+print "s", s;
+print "v", v;