buildstream/_frontend/cli.py

@@ -170,6 +170,31 @@ original_main = click.BaseCommand.main
 click.BaseCommand.main = override_main
 
 
+def get_elements(app):
+    directory = app._main_options.get("directory")
+    project_conf = app.project._project_conf
+    output = []
+
+    # The project is not required to have an element-path
+    element_directory = project_conf.get('element-path')
+
+    # The project may have a default element defined
+    default_element = project_conf.get("defaults", {}).get("target-element", None)
+
+    if default_element:
+        return (default_element,)
+
+    directory = os.path.abspath(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("./")
+                rel_file = rel_file.lstrip(element_directory).lstrip('/')
+                output.append(rel_file)
+    return tuple(output)
+
+
 ##################################################################
 #                          Main Options                          #
 ##################################################################
@@ -509,6 +534,11 @@ 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.
 
@@ -553,7 +583,11 @@ def show(app, elements, deps, except_, order, format_):
         bst show target.bst --format \\
             $'---------- %{name} ----------\\n%{vars}'
     """
+
     with app.initialized():
+        if not elements:
+            elements = get_elements(app)
+
         dependencies = app.stream.load_selection(elements,
                                                  selection=deps,
                                                  except_targets=except_)

buildstream/_project.py

@@ -226,7 +226,7 @@ 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',

buildstream/data/projectconfig.yaml

@@ -196,4 +196,11 @@ shell:
 
   # Command to run when `bst shell` does not provide a command
   #
-  command: [ 'sh', '-i' ]
\ No newline at end of file
+  command: [ 'sh', '-i' ]
+
+# Default Targets
+#
+defaults:
+
+  # Set a Default element to build when none are defined 
+  target-element: None

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 +46,33 @@ 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)
+    prev_dir = os.getcwd()
+    os.chdir(project)
+    result = cli.run(project=project, silent=True, args=[
+        'show'])
+    os.chdir(prev_dir)
+
+    result.assert_success()
+    results = result.output.strip().splitlines()
+    expected = 'buildable ca4321107f0f529170d345af19372c57a6672f62afdcbdd36ca067b67124ef60 target2.bst'
+    if result.output.strip() != expected:
+        raise AssertionError("Expected output:\n{}\nInstead received output:\n{}"
+                             .format(expected, result.output))
+
+
+@pytest.mark.datafiles(DATA_DIR + "_fail")
+def test_show_fail(cli, datafiles):
+    project = os.path.join(datafiles.dirname, datafiles.basename)
+    prev_dir = os.getcwd()
+    os.chdir(project)
+    result = cli.run(project=project, silent=True, args=[
+        'show'])
+    os.chdir(prev_dir)
+
     result.assert_main_error(ErrorDomain.LOAD, LoadErrorReason.INVALID_DATA)