packaging: process Inno Setup files with Jinja2

I want to make the Inno Setup files dynamically generated.
This will enable us to do things like automatically derive the
set of files to be packaged instead of having to manually
keep lists of files in sync across installers.

As the first step towards this, we process the Inno Setup
files with Jinja2.

As part of this conversion, we had to escape syntax in
mercurial.iss that conflicts with Jinja2. I also took the
opportunity to include modpath.iss via Jinja2 instead of
using Inno's preprocessor. This keeps the Python code a
bit simpler.

Differential Revision: https://phab.mercurial-scm.org/D7158

contrib/packaging/hgpackaging/inno.py

@@ -12,6 +12,8 b' import pathlib'
 import shutil
 import subprocess
 
+import jinja2
+
 from .py2exe import build_py2exe
 from .util import find_vc_runtime_files
 
@@ -75,9 +77,26 b' def build('
 
     print('creating installer')
 
-    # Copy Inno files into place.
-    for p in ('mercurial.iss', 'modpath.iss'):
-        shutil.copyfile(inno_source_dir / p, inno_build_dir / p)
+    # Install Inno files by rendering a template.
+    jinja_env = jinja2.Environment(
+        loader=jinja2.FileSystemLoader(str(inno_source_dir)),
+        # Need to change these to prevent conflict with Inno Setup.
+        comment_start_string='{##',
+        comment_end_string='##}',
+    )
+
+    try:
+        template = jinja_env.get_template('mercurial.iss')
+    except jinja2.TemplateSyntaxError as e:
+        raise Exception(
+            'template syntax error at %s:%d: %s'
+            % (e.name, e.lineno, e.message,)
+        )
+
+    content = template.render()
+
+    with (inno_build_dir / 'mercurial.iss').open('w', encoding='utf-8') as fh:
+        fh.write(content)
 
     args = [str(iscc_exe)]
 

contrib/packaging/inno/mercurial.iss

@@ -40,7 +40,7 b' AppPublisher=Matt Mackall and others'
 AppPublisherURL=https://mercurial-scm.org/
 AppSupportURL=https://mercurial-scm.org/
 AppUpdatesURL=https://mercurial-scm.org/
-AppID={{4B95A5F1-EF59-4B08-BED8-C891C46121B3}
+{{ 'AppID={{4B95A5F1-EF59-4B08-BED8-C891C46121B3}' }}
 AppContact=[e-mail]
 DefaultDirName={pf}\Mercurial
 SourceDir=..\..
@@ -121,4 +121,5 b' begin'
     setArrayLength(Result, 1)
     Result[0] := ExpandConstant('{app}');
 end;
-#include "modpath.iss"
+
+{% include 'modpath.iss' %}