NEWS

@@ -12,6 +12,10 @@ buildstream 1.3.1
     specific. Recommendation if you are building in Linux is to use the
     ones being used in freedesktop-sdk project, for example
 
+  o Running `bst show` without elements specified will now attempt to show
+    the default element defined in the projcet configuration.
+    If no default element is defined, all elements in the project will be shown
+
   o All elements must now be suffixed with `.bst`
     Attempting to use an element that does not have the `.bst` extension,
     will result in a warning.

buildstream/_frontend/cli.py

@@ -526,6 +526,11 @@ def push(app, elements, deps, remote):
 def show(app, elements, deps, except_, order, format_):
     """Show elements in the pipeline
 
+    Declaring no elements with result in showing a default element if one is declared in the project configuration.
+
+    If no default is declared, all elements in the project will be shown
+
+
     By default this will show all of the dependencies of the
     specified target element.
 
@@ -570,11 +575,14 @@ def show(app, elements, deps, except_, order, format_):
         bst show target.bst --format \\
             $'---------- %{name} ----------\\n%{vars}'
     """
+
     with app.initialized():
         if not elements:
             guessed_target = app.context.guess_element()
             if guessed_target:
                 elements = (guessed_target,)
+            else:
+                elements = app.project.get_default_elements()
 
         dependencies = app.stream.load_selection(elements,
                                                  selection=deps,

buildstream/_project.py

@@ -228,7 +228,7 @@ class Project():
             'element-path', 'variables',
             'environment', 'environment-nocache',
             'split-rules', 'elements', 'plugins',
-            'aliases', 'name',
+            'aliases', 'name', 'defaults',
             'artifacts', 'options',
             'fail-on-overlap', 'shell', 'fatal-warnings',
             'ref-storage', 'sandbox', 'mirrors', 'remote-execution',
@@ -391,6 +391,34 @@ class Project():
         # Reset the element loader state
         Element._reset_load_state()
 
+    # get_default_elements()
+    #
+    # This function is used to gather either:
+    # The project default element (if defined in project.conf)
+    # or
+    # All elements in the project
+    #
+    def get_default_elements(self):
+        output = []
+
+        # The project is not required to have an element-path
+        element_directory = self._project_conf.get('element-path')
+
+        # The project may have a default element defined
+        default_element = self._project_conf.get("defaults", {}).get("target-element", None)
+
+        if default_element:
+            return (default_element,)
+
+        directory = os.path.join(self.directory, element_directory)
+        for root, _, files in os.walk(directory):
+            for file in files:
+                if file.endswith(".bst"):
+                    rel_dir = os.path.relpath(root, directory)
+                    rel_file = os.path.join(rel_dir, file).lstrip("./")
+                    output.append(rel_file)
+        return tuple(output)
+
     # _load():
     #
     # Loads the project configuration file in the project

tests/frontend/project_default/elements/target.bst

+kind: stack
+description: |
+
+  Main stack target for the bst build test

tests/frontend/project_default/elements/target2.bst

+kind: stack
+description: |
+
+  Main stack target for the bst build test

tests/frontend/project_default/project.conf

+# Project config for frontend build test
+name: test
+
+element-path: elements
+
+fatal-warnings:
+- bad-element-suffix
+
+defaults:
+ target-element: target2.bst

tests/frontend/project_fail/elements/compose-all.bst

+kind: compose
+
+depends:
+- fileNAME: import-dev.bst
+  type: build
+
+config:
+  # Dont try running the sandbox, we dont have a
+  # runtime to run anything in this context.
+  integrate: False

tests/frontend/project_fail/elements/import-dev.bst

+kind: import
+sources:
+- kind: local
+  path: files/dev-files

tests/frontend/project_fail/elements/target.bst

+kind: stack
+description: |
+
+  Main stack target for the bst build test
+
+depends:
+- compose-all.bst

tests/frontend/project_fail/files/dev-files/usr/include/pony.h

+#ifndef __PONY_H__
+#define __PONY_H__
+
+#define PONY_BEGIN "Once upon a time, there was a pony."
+#define PONY_END "And they lived happily ever after, the end."
+
+#define MAKE_PONY(story)  \
+  PONY_BEGIN \
+  story \
+  PONY_END
+
+#endif /* __PONY_H__ */

tests/frontend/project_fail/project.conf

+# Project config for frontend build test
+name: test
+
+element-path: elements

tests/frontend/show.py

@@ -46,6 +46,27 @@ def test_show_invalid_element_path(cli, datafiles):
         'show',
         "foo.bst"])
 
+
+@pytest.mark.datafiles(DATA_DIR + "_default")
+def test_show_default(cli, datafiles):
+    project = os.path.join(datafiles.dirname, datafiles.basename)
+    result = cli.run(project=project, silent=True, args=[
+        'show'])
+
+    result.assert_success()
+
+    # Get the result output of "[state sha element]" and turn into a list
+    results = result.output.strip().split(" ")
+    expected = 'target2.bst'
+    assert results[2] == expected
+
+
+@pytest.mark.datafiles(DATA_DIR + "_fail")
+def test_show_fail(cli, datafiles):
+    project = os.path.join(datafiles.dirname, datafiles.basename)
+    result = cli.run(project=project, silent=True, args=[
+        'show'])
+
     result.assert_main_error(ErrorDomain.LOAD, LoadErrorReason.INVALID_DATA)