Add support for optional fields

3 files changed, 10 insertions, 0 deletions

diff --git a/doc/property_replacer.html b/doc/property_replacer.html
index 943c4f73..217b6dc0 100644
--- a/doc/property_replacer.html
+++ b/doc/property_replacer.html
@@ -714,6 +714,10 @@ Useful for secure pathname generation (with dynafiles).
 Useful for secure pathname generation (with dynafiles).
 </td>
 </tr>
+<tr>
+<td><b>optional-field</b></td>
+<td>In templates that are used for building field lists (in particular, ommongodb), completely remove this field if the corresponding property is not present.  Currently implemented only for the <b>$!&lt;name&gt;</b> properties.</td>
+</tr>
 </tbody>
 </table>
 <p>To use multiple options, simply place them one after each other with a comma delmimiting
diff --git a/template.c b/template.c
index 80427350..bd622285 100644
--- a/template.c
+++ b/template.c
@@ -663,6 +663,8 @@ static void doOptions(unsigned char **pp, struct templateEntry *pTpe)
 			} else {
 				pTpe->data.field.options.bJSONf = 1;
 			}
+		 } else if(!strcmp((char*)Buf, "optional-field")) {
+			 pTpe->data.field.options.bOptionalField = 1;
 		 } else {
 			dbgprintf("Invalid field option '%s' specified - ignored.\n", Buf);
 		 }
@@ -1988,6 +1990,9 @@ void tplPrintList(rsconf_t *conf)
 				if(pTpe->data.field.options.bJSONf) {
 					dbgprintf("[format as JSON field] ");
 				}
+				if(pTpe->data.field.options.bOptionalField) {
+					dbgprintf("[optional field - skip in field template if not present] ");
+				}
 				if(pTpe->data.field.options.bDropLastLF) {
 				  	dbgprintf("[drop last LF in msg] ");
 				}
diff --git a/template.h b/template.h
index a4b5658e..0d083216 100644
--- a/template.h
+++ b/template.h
@@ -115,6 +115,7 @@ struct templateEntry {
 				unsigned bCSV: 1;		/* format field in CSV (RFC 4180) format */
 				unsigned bJSON: 1;		/* format field JSON escaped */
 				unsigned bJSONf: 1;		/* format field JSON *field* (n/v pair) */
+				unsigned bOptionalField: 1;	/* optional field - skip in field template if not present */
 			} options;		/* options as bit fields */
 		} field;
 	} data;