Greater customization of GHCi prompt

This patch is trying to redesign the :set prompt option to take not a
String but a Haskell function, like [String] -> Int -> IO String, where
[String] is the list of the names of the currently loaded modules and
Int is the line number. Currently you may set prompt function with
**:set promt-function [String] -> Int -> IO String** option and old
version is also available - :set prompt String.

So, it looks like I've almost completed this patch:

1) Now we have a lot of escape sequences - 13 to be exact. Most of them
   are similar to bash prompt escape sequences. Thus they are quite handy.

2) We may use the special escape sequence to call shell functions, for
   example "%call(ls -l -a)".

3) We may use :set prompt-function to set PFunction to handle prompt.
   It is just [String] -> Int -> IO String.

Reviewers: erikd, austin, mpickering, bgamari

Reviewed By: mpickering, bgamari

Subscribers: mpickering, thomie

Differential Revision: https://phabricator.haskell.org/D2084

GHC Trac Issues: #5850

6 files changed, 41 insertions, 0 deletions

diff --git a/testsuite/tests/ghci/scripts/all.T b/testsuite/tests/ghci/scripts/all.T
index 2d21772434..6e9e91bec4 100755
--- a/testsuite/tests/ghci/scripts/all.T
+++ b/testsuite/tests/ghci/scripts/all.T
@@ -92,6 +92,9 @@ test('ghci056',
 
 test('ghci057', extra_hc_opts('-fwarn-tabs'), ghci_script, ['ghci057.script'])
 
+test('ghci060', normal, ghci_script, ['ghci060.script'])
+test('ghci061', normal, ghci_script, ['ghci061.script'])
+
 test('T2452', normal, ghci_script, ['T2452.script'])
 test('T2766', normal, ghci_script, ['T2766.script'])
 
diff --git a/testsuite/tests/ghci/scripts/ghci060.script b/testsuite/tests/ghci/scripts/ghci060.script
new file mode 100644
index 0000000000..853512e1c7
--- /dev/null
+++ b/testsuite/tests/ghci/scripts/ghci060.script
@@ -0,0 +1,7 @@
+:set prompt "%call()> "
+:set prompt "%call(pwd) %call()"
+:set prompt "%callasfasfasfsaf(pwd)"
+:set prompt "%call(pwd"
+:set prompt "%a> "
+:set prompt-cont "%call()| "
+:set prompt-cont "%t| "
diff --git a/testsuite/tests/ghci/scripts/ghci060.stderr b/testsuite/tests/ghci/scripts/ghci060.stderr
new file mode 100644
index 0000000000..8f77a033d4
--- /dev/null
+++ b/testsuite/tests/ghci/scripts/ghci060.stderr
@@ -0,0 +1,5 @@
+Incorrect %call syntax. Should be %call(a command and arguments).
+Incorrect %call syntax. Should be %call(a command and arguments).
+Incorrect %call syntax. Should be %call(a command and arguments).
+Incorrect %call syntax. Should be %call(a command and arguments).
+Incorrect %call syntax. Should be %call(a command and arguments).
diff --git a/testsuite/tests/ghci/scripts/ghci061.hs b/testsuite/tests/ghci/scripts/ghci061.hs
new file mode 100644
index 0000000000..2779bb5d1f
--- /dev/null
+++ b/testsuite/tests/ghci/scripts/ghci061.hs
@@ -0,0 +1,5 @@
+two_args :: [String] -> IO String
+two_args _ = return "two_args> "
+
+three_args :: [String] -> Int -> IO String
+three_args _ _ = return $ "three_args> "
diff --git a/testsuite/tests/ghci/scripts/ghci061.script b/testsuite/tests/ghci/scripts/ghci061.script
new file mode 100644
index 0000000000..2d96b16ba4
--- /dev/null
+++ b/testsuite/tests/ghci/scripts/ghci061.script
@@ -0,0 +1,5 @@
+:l ghci061.hs
+:set prompt-function two_args
+:set prompt-function three_args
+:set prompt-cont-function two_args
+:set prompt-cont-function three_args
diff --git a/testsuite/tests/ghci/scripts/ghci061.stderr b/testsuite/tests/ghci/scripts/ghci061.stderr
new file mode 100644
index 0000000000..1ba00c5609
--- /dev/null
+++ b/testsuite/tests/ghci/scripts/ghci061.stderr
@@ -0,0 +1,16 @@
+
+<interactive>:1:2: error:
+    • Couldn't match type ‘IO String’ with ‘Int -> IO String’
+      Expected type: [String] -> Int -> IO String
+        Actual type: [String] -> IO String
+    • In the expression: (two_args) :: [String] -> Int -> IO String
+      In an equation for ‘_compileParsedExpr’:
+          _compileParsedExpr = (two_args) :: [String] -> Int -> IO String
+
+<interactive>:1:2: error:
+    • Couldn't match type ‘IO String’ with ‘Int -> IO String’
+      Expected type: [String] -> Int -> IO String
+        Actual type: [String] -> IO String
+    • In the expression: (two_args) :: [String] -> Int -> IO String
+      In an equation for ‘_compileParsedExpr’:
+          _compileParsedExpr = (two_args) :: [String] -> Int -> IO String