extension: add a `required` suboption to enforce the use of an extensions

extension: add a `required` suboption to enforce the use of an extensions

If `required` is set, failing to load an extensions will abort. See the test
and documentation for details.

Differential Revision: https://phab.mercurial-scm.org/D11822

--- a/mercurial/configitems.py	Mon Nov 29 13:09:04 2021 +0100
+++ b/mercurial/configitems.py	Fri Nov 26 17:17:49 2021 +0100
@@ -1286,6 +1286,12 @@
     generic=True,
 )
 coreconfigitem(
+    b'extensions',
+    b'[^:]*:required',
+    default=False,
+    generic=True,
+)
+coreconfigitem(
     b'extdata',
     b'.*',
     default=None,

--- a/mercurial/extensions.py	Mon Nov 29 13:09:04 2021 +0100
+++ b/mercurial/extensions.py	Fri Nov 26 17:17:49 2021 +0100
@@ -314,10 +314,23 @@
                 else:
                     error_msg = _(b'failed to import extension "%s": %s')
                     error_msg %= (name, msg)
-                ui.warn((b"*** %s\n") % error_msg)
-                if isinstance(inst, error.Hint) and inst.hint:
-                    ui.warn(_(b"*** (%s)\n") % inst.hint)
-                ui.traceback()
+
+                ext_options = ui.configsuboptions(b"extensions", name)[1]
+                if stringutil.parsebool(ext_options.get(b"required", b'no')):
+                    hint = None
+                    if isinstance(inst, error.Hint) and inst.hint:
+                        hint = inst.hint
+                    if hint is None:
+                        hint = _(
+                            b"loading of this extension was required, "
+                            b"see `hg help config.extensions` for details"
+                        )
+                    raise error.Abort(error_msg, hint=hint)
+                else:
+                    ui.warn((b"*** %s\n") % error_msg)
+                    if isinstance(inst, error.Hint) and inst.hint:
+                        ui.warn(_(b"*** (%s)\n") % inst.hint)
+                    ui.traceback()
 
     ui.log(
         b'extension',

--- a/mercurial/helptext/config.txt	Mon Nov 29 13:09:04 2021 +0100
+++ b/mercurial/helptext/config.txt	Fri Nov 26 17:17:49 2021 +0100
@@ -850,6 +850,17 @@
   # (this extension will get loaded from the file specified)
   myfeature = ~/.hgext/myfeature.py
 
+If an extension fails to load, a warning will be issued, and Mercurial will
+proceed. To enforce that an extension must be loaded, one can set the `required`
+suboption in the config::
+
+  [extensions]
+  myfeature = ~/.hgext/myfeature.py
+  myfeature:required = yes
+
+To debug extension loading issue, one can add `--traceback` to their mercurial
+invocation.
+
 
 ``format``
 ----------

--- a/tests/test-extension.t	Mon Nov 29 13:09:04 2021 +0100
+++ b/tests/test-extension.t	Fri Nov 26 17:17:49 2021 +0100
@@ -1944,3 +1944,94 @@
   hg: unknown command 'dummy'
   (did you mean summary?)
   [10]
+
+Check the mandatory extension feature
+-------------------------------------
+
+  $ hg init mandatory-extensions
+  $ cat > $TESTTMP/mandatory-extensions/.hg/good.py << EOF
+  > pass
+  > EOF
+  $ cat > $TESTTMP/mandatory-extensions/.hg/bad.py << EOF
+  > raise RuntimeError("babar")
+  > EOF
+  $ cat > $TESTTMP/mandatory-extensions/.hg/syntax.py << EOF
+  > def (
+  > EOF
+
+Check that the good one load :
+
+  $ cat > $TESTTMP/mandatory-extensions/.hg/hgrc << EOF
+  > [extensions]
+  > good = $TESTTMP/mandatory-extensions/.hg/good.py
+  > EOF
+
+  $ hg -R mandatory-extensions id
+  000000000000 tip
+
+Make it mandatory to load
+
+  $ cat >> $TESTTMP/mandatory-extensions/.hg/hgrc << EOF
+  > good:required = yes
+  > EOF
+
+  $ hg -R mandatory-extensions id
+  000000000000 tip
+
+Check that the bad one does not load
+
+  $ cat >> $TESTTMP/mandatory-extensions/.hg/hgrc << EOF
+  > bad = $TESTTMP/mandatory-extensions/.hg/bad.py
+  > EOF
+
+  $ hg -R mandatory-extensions id
+  *** failed to import extension "bad" from $TESTTMP/mandatory-extensions/.hg/bad.py: babar
+  000000000000 tip
+
+Make it mandatory to load
+
+  $ cat >> $TESTTMP/mandatory-extensions/.hg/hgrc << EOF
+  > bad:required = yes
+  > EOF
+
+  $ hg -R mandatory-extensions id
+  abort: failed to import extension "bad" from $TESTTMP/mandatory-extensions/.hg/bad.py: babar
+  (loading of this extension was required, see `hg help config.extensions` for details)
+  [255]
+
+Make it not mandatory to load
+
+  $ cat >> $TESTTMP/mandatory-extensions/.hg/hgrc << EOF
+  > bad:required = no
+  > EOF
+
+  $ hg -R mandatory-extensions id
+  *** failed to import extension "bad" from $TESTTMP/mandatory-extensions/.hg/bad.py: babar
+  000000000000 tip
+
+Same check with the syntax error one
+
+  $ cat >> $TESTTMP/mandatory-extensions/.hg/hgrc << EOF
+  > bad = !
+  > syntax = $TESTTMP/mandatory-extensions/.hg/syntax.py
+  > syntax:required = yes
+  > EOF
+
+  $ hg -R mandatory-extensions id
+  abort: failed to import extension "syntax" from $TESTTMP/mandatory-extensions/.hg/syntax.py: invalid syntax (*syntax.py, line 1) (glob)
+  (loading of this extension was required, see `hg help config.extensions` for details)
+  [255]
+
+Same check with a missing one
+
+  $ cat >> $TESTTMP/mandatory-extensions/.hg/hgrc << EOF
+  > syntax = !
+  > syntax:required =
+  > missing = foo/bar/baz/I/do/not/exist/
+  > missing:required = yes
+  > EOF
+
+  $ hg -R mandatory-extensions id
+  abort: failed to import extension "missing" from foo/bar/baz/I/do/not/exist/: [Errno 2] $ENOENT$: 'foo/bar/baz/I/do/not/exist'
+  (loading of this extension was required, see `hg help config.extensions` for details)
+  [255]