Minor updates to validation command (#273)

* Added validation section to README.md, error logic if womtool and miniwdl are disabled

* Clearer error message, added assert_can_communicate_with_server function

---------

Co-authored-by: bshifaw <[email protected]>

README.md

@@ -113,6 +113,13 @@ Cromshell is a CLI for submitting workflows to a Cromwell server and monitoring/
      * `-c/--color` Color outliers in task level cost results.
      * `-d/--detailed` Get the cost for a workflow at the task level.
 
+   #### Validate WDL
+   * `validate [wdl] [input json] --dependencies-zip [wdl_zip_file]`
+     * Validate a WDL file.
+     * Runs both miniwdl and womtool validation by default, but can be configured to run only one or the other.
+     * Womtool validation via Cromwell server API does not support validation of imported files, however miniwdl does.
+     * `--dependencies-zip`  MiniWDL option: ZIP file or directory containing workflow source files that are used to resolve local imports.
+
 ## Features:
  * Running `submit` will create a new folder in the `~/.cromshell/${CROMWELL_URL}/` directory named with the cromwell job id of the newly submitted job.  
  It will copy your wdl and json inputs into the folder for reproducibility.  

src/cromshell/validate/command.py

@@ -3,6 +3,7 @@
 
 import click
 
+import cromshell.utilities.http_utils as http_utils
 import cromshell.utilities.miniwdl_utils as miniwdl
 import cromshell.utilities.womtool_utils as womtool
 
@@ -80,11 +81,23 @@ def main(
 
     return_code = 0
 
+    if no_womtool and no_miniwdl:
+        LOGGER.error(
+            "Both `--no-womtool` and `--no-miniwdl` options were used but"
+            "at least one validation tool must be enabled."
+        )
+        raise MissingArgumentError(
+            "Both `--no-womtool` and `--no-miniwdl` options were used but "
+            "at least one validation tool must be enabled."
+        )
+
     if not no_womtool:
         if not wdl_json:
             LOGGER.error("WDL JSON file is required.")
             raise MissingArgumentError("WDL JSON file is required.")
 
+        http_utils.assert_can_communicate_with_server(config)
+
         womtool.womtool_validate_wdl_and_json(
             wdl=str(wdl), wdl_json=str(wdl_json), config=config
         )