fix:web: make --base-url work again [#2127], [#2100]

hledger-web/Hledger/Web/App.hs

@@ -102,7 +102,21 @@ type Form a = Html -> MForm Handler (FormResult a, Widget)
 -- Please see the documentation for the Yesod typeclass. There are a number
 -- of settings which can be configured by overriding methods here.
 instance Yesod App where
-  approot = guessApprootOr (ApprootMaster $ appRoot . settings)
+
+  -- Configure the app root, AKA base url, which is prepended to relative hyperlinks.
+  -- Broadly, we'd like this:
+  -- 1. when --base-url has been specified, use that;
+  -- 2. otherwise, guess it from request headers, which helps us respond from the
+  --    same hostname/IP address when hledger-web is accessible at multiple IPs;
+  -- 3. otherwise, leave it empty (relative links stay relative).
+  -- But it's hard to see how to achieve this.
+  -- For now we do (I believe) 1 or 3, with 2 unfortunately not supported.
+  -- Issues include: #2099, #2100, #2127
+  approot =
+    -- ApprootRelative
+    -- ApprootMaster $ appRoot . settings
+    -- guessApprootOr (ApprootMaster $ appRoot . settings)
+    ApprootMaster $ \(App{settings=AppConfig{appRoot=r}, appOpts=WebOpts{base_url_=bu}}) -> if null bu then r else T.pack bu
 
   makeSessionBackend _ = do
     hledgerdata <- getXdgDirectory XdgCache "hledger"

hledger-web/Hledger/Web/Test.hs

@@ -144,19 +144,23 @@ hledgerWebTest = do
       bodyContains "id=\"transaction-2-1\""
       bodyContains "id=\"transaction-2-2\""
 
-  runTests "hledger-web with --base-url"
-    [("base-url","https://base")] nulljournal $ do
-
-    yit "hyperlinks respect --base-url" $ do
-      get JournalR
-      statusIs 200
-      bodyContains "href=\"https://base"
-      bodyContains "src=\"https://base"
+  -- #2127
+  -- XXX I'm pretty sure this test lies, ie does not match production behaviour.
+  -- (test with curl -s http://localhost:5000/journal | rg '(href)="[\w/].*?"' -o )
+  -- App root setup is a maze of twisty passages, all alike.
+  -- runTests "hledger-web with --base-url"
+  --   [("base-url","https://base")] nulljournal $ do
+  --   yit "hyperlinks respect --base-url" $ do
+  --     get JournalR
+  --     statusIs 200
+  --     bodyContains "href=\"https://base"
+  --     bodyContains "src=\"https://base"
 
   -- #2139
+  -- XXX Not passing.
+  -- Static root setup is a maze of twisty passages, all different.
   -- runTests "hledger-web with --base-url, --file-url"
   --   [("base-url","https://base"), ("file-url","https://files")] nulljournal $ do
-
   --   yit "static file hyperlinks respect --file-url, others respect --base-url" $ do
   --     get JournalR
   --     statusIs 200