test: Add unittest spec for option.c (#5289)

Move typedef expand_T to types.h for tests
Fix lint error for old style comments

Describe 'check_ff_value' valid values as an initial test.

Fix 'get_sts_value' comment inaccuracy and add unit test for it

4 files changed, 82 insertions, 35 deletions

diff --git a/src/nvim/ex_cmds_defs.h b/src/nvim/ex_cmds_defs.h
index c2e7add287..8148eb5cee 100644
--- a/src/nvim/ex_cmds_defs.h
+++ b/src/nvim/ex_cmds_defs.h
@@ -126,39 +126,36 @@ struct exarg {
   struct condstack *cstack;     ///< condition stack for ":if" etc.
 };
 
-#define FORCE_BIN 1             /* ":edit ++bin file" */
-#define FORCE_NOBIN 2           /* ":edit ++nobin file" */
-
-/* Values for "flags" */
-#define EXFLAG_LIST     0x01    /* 'l': list */
-#define EXFLAG_NR       0x02    /* '#': number */
-#define EXFLAG_PRINT    0x04    /* 'p': print */
-
-/*
- * used for completion on the command line
- */
-typedef struct expand {
-  int xp_context;                       /* type of expansion */
-  char_u      *xp_pattern;              /* start of item to expand */
-  int xp_pattern_len;                   /* bytes in xp_pattern before cursor */
-  char_u      *xp_arg;                  /* completion function */
-  int xp_scriptID;                      /* SID for completion function */
-  int xp_backslash;                     /* one of the XP_BS_ values */
+#define FORCE_BIN 1             // ":edit ++bin file"
+#define FORCE_NOBIN 2           // ":edit ++nobin file"
+
+// Values for "flags"
+#define EXFLAG_LIST     0x01    // 'l': list
+#define EXFLAG_NR       0x02    // '#': number
+#define EXFLAG_PRINT    0x04    // 'p': print
+
+// used for completion on the command line
+struct expand {
+  int xp_context;               // type of expansion
+  char_u *xp_pattern;           // start of item to expand
+  int xp_pattern_len;           // bytes in xp_pattern before cursor
+  char_u *xp_arg;               // completion function
+  int xp_scriptID;              // SID for completion function
+  int xp_backslash;             // one of the XP_BS_ values
 #ifndef BACKSLASH_IN_FILENAME
-  int xp_shell;                         /* TRUE for a shell command, more
-                                           characters need to be escaped */
+  int xp_shell;                 // TRUE for a shell command, more
+                                // characters need to be escaped
 #endif
-  int xp_numfiles;                      /* number of files found by
-                                                    file name completion */
-  char_u      **xp_files;               /* list of files */
-  char_u      *xp_line;                 /* text being completed */
-  int xp_col;                           /* cursor position in line */
-} expand_T;
-
-/* values for xp_backslash */
-#define XP_BS_NONE      0       /* nothing special for backslashes */
-#define XP_BS_ONE       1       /* uses one backslash before a space */
-#define XP_BS_THREE     2       /* uses three backslashes before a space */
+  int xp_numfiles;              // number of files found by file name completion
+  char_u **xp_files;            // list of files
+  char_u *xp_line;              // text being completed
+  int xp_col;                   // cursor position in line
+};
+
+// values for xp_backslash
+#define XP_BS_NONE      0       // nothing special for backslashes
+#define XP_BS_ONE       1       // uses one backslash before a space
+#define XP_BS_THREE     2       // uses three backslashes before a space
 
 /// Command modifiers ":vertical", ":browse", ":confirm", ":hide", etc. set a
 /// flag.  This needs to be saved for recursive commands, put them in a
diff --git a/src/nvim/option.c b/src/nvim/option.c
index e53dbfc75a..1ef1c300b9 100644
--- a/src/nvim/option.c
+++ b/src/nvim/option.c
@@ -6585,10 +6585,8 @@ int get_sw_value(buf_T *buf)
   return (int)result;
 }
 
-/*
- * Return the effective softtabstop value for the current buffer, using the
- * 'tabstop' value when 'softtabstop' is negative.
- */
+// Return the effective softtabstop value for the current buffer,
+// using the effective shiftwidth  value when 'softtabstop' is negative.
 int get_sts_value(void)
 {
   long result = curbuf->b_p_sts < 0 ? get_sw_value(curbuf) : curbuf->b_p_sts;
diff --git a/src/nvim/types.h b/src/nvim/types.h
index bfe8be2091..35a5d1e2bd 100644
--- a/src/nvim/types.h
+++ b/src/nvim/types.h
@@ -13,4 +13,5 @@ typedef unsigned char char_u;
 // Can hold one decoded UTF-8 character.
 typedef uint32_t u8char_T;
 
+typedef struct expand expand_T;
 #endif  // NVIM_TYPES_H
diff --git a/test/unit/option_spec.lua b/test/unit/option_spec.lua
new file mode 100644
index 0000000000..8bab0194a2
--- /dev/null
+++ b/test/unit/option_spec.lua
@@ -0,0 +1,51 @@
+local helpers = require("test.unit.helpers")
+
+local to_cstr = helpers.to_cstr
+local eq      = helpers.eq
+
+local option = helpers.cimport("./src/nvim/option.h")
+local globals = helpers.cimport("./src/nvim/globals.h")
+
+local check_ff_value = function(ff)
+  return option.check_ff_value(to_cstr(ff))
+end
+
+describe('check_ff_value', function()
+
+  it('views empty string as valid', function()
+    eq(1, check_ff_value(""))
+  end)
+
+  it('views "unix", "dos" and "mac" as valid', function()
+    eq(1, check_ff_value("unix"))
+    eq(1, check_ff_value("dos"))
+    eq(1, check_ff_value("mac"))
+  end)
+
+  it('views "foo" as invalid', function()
+    eq(0, check_ff_value("foo"))
+  end)
+end)
+
+describe('get_sts_value', function()
+  it([[returns 'softtabstop' when it is non-negative]], function()
+    globals.curbuf.b_p_sts = 5
+    eq(5, option.get_sts_value())
+
+    globals.curbuf.b_p_sts = 0
+    eq(0, option.get_sts_value())
+  end)
+
+  it([[returns "effective shiftwidth" when 'softtabstop' is negative]], function()
+    local shiftwidth = 2
+    globals.curbuf.b_p_sw = shiftwidth
+    local tabstop = 5
+    globals.curbuf.b_p_ts = tabstop
+    globals.curbuf.b_p_sts = -2
+    eq(shiftwidth, option.get_sts_value())
+
+    shiftwidth = 0
+    globals.curbuf.b_p_sw = shiftwidth
+    eq(tabstop, option.get_sts_value())
+  end)
+end)