Issue #18365: Add mock Text class and test thereof versus tk.Text.

Based on patches by Todd.Rovito and Phil Webster.

Author: terryjreedy

Lib/idlelib/idle_test/mock_tk.py

@@ -1,4 +1,5 @@
 """Classes that replace tkinter gui objects used by an object being tested.
+
 A gui object is anything with a master or parent paramenter, which is typically
 required in spite of what the doc strings say.
 """
@@ -15,8 +16,10 @@ def get(self):
         return self.value
 
 class Mbox_func:
-    """Generic mock for messagebox functions. All have same call signature.
-    Mbox instantiates once for each function. Tester uses attributes.
+    """Generic mock for messagebox functions, which all have the same signature.
+
+    Instead of displaying a message box, the mock's call method saves the
+    arguments as instance attributes, which test functions can then examime.
     """
     def __init__(self):
         self.result = None  # The return for all show funcs
@@ -30,6 +33,7 @@ def __call__(self, title, message, *args, **kwds):
 
 class Mbox:
     """Mock for tkinter.messagebox with an Mbox_func for each function.
+
     This module was 'tkMessageBox' in 2.x; hence the 'import as' in  3.x.
     Example usage in test_module.py for testing functios in module.py:
     ---
@@ -49,9 +53,9 @@ def setUpClass(cls):
     def tearDownClass(cls):
         module.tkMessageBox = orig_mbox
     ---
-    When tkMessageBox functions are the only gui making calls in a method,
-    this replacement makes the method gui-free and unit-testable.
-    For 'ask' functions, set func.result return before calling method.
+    For 'ask' functions, set func.result return value before calling the method
+    that uses the message function. When tkMessageBox functions are the
+    only gui alls in a method, this replacement makes the method gui-free,
     """
     askokcancel = Mbox_func()     # True or False
     askquestion = Mbox_func()     # 'yes' or 'no'
@@ -61,3 +65,215 @@ def tearDownClass(cls):
     showerror = Mbox_func()    # None
     showinfo = Mbox_func()     # None
     showwarning = Mbox_func()  # None
+
+from _tkinter import TclError
+
+class Text:
+    """A semi-functional non-gui replacement for tkinter.Text text editors.
+
+    The mock's data model is that a text is a list of \n-terminated lines.
+    The mock adds an empty string at  the beginning of the list so that the
+    index of actual lines start at 1, as with Tk. The methods never see this.
+    Tk initializes files with a terminal \n that cannot be deleted. It is
+    invisible in the sense that one cannot move the cursor beyond it.
+
+    This class is only tested (and valid) with strings of ascii chars.
+    For testing, we are not concerned with Tk Text's treatment of,
+    for instance, 0-width characters or character + accent.
+   """
+    def __init__(self, master=None, cnf={}, **kw):
+        '''Initialize mock, non-gui, text-only Text widget.
+
+        At present, all args are ignored. Almost all affect visual behavior.
+        There are just a few Text-only options that affect text behavior.
+        '''
+        self.data = ['', '\n']
+
+    def index(self, index):
+        "Return string version of index decoded according to current text."
+        return "%s.%s" % self._decode(index, endflag=1)
+
+    def _decode(self, index, endflag=0):
+        """Return a (line, char) tuple of int indexes into self.data.
+
+        This implements .index without converting the result back to a string.
+        The result is contrained by the number of lines and linelengths of
+        self.data. For many indexes, the result is initally (1, 0).
+
+        The input index may have any of several possible forms:
+        * line.char float: converted to 'line.char' string;
+        * 'line.char' string, where line and char are decimal integers;
+        * 'line.char lineend', where lineend='lineend' (and char is ignored);
+        * 'line.end', where end='end' (same as above);
+        * 'insert', the positions before terminal \n;
+        * 'end', whose meaning depends on the endflag passed to ._endex.
+        * 'sel.first' or 'sel.last', where sel is a tag -- not implemented.
+        """
+        if isinstance(index, (float, bytes)):
+            index = str(index)
+        try:
+            index=index.lower()
+        except AttributeError:
+            raise TclError('bad text index "%s"' % index) from None
+
+        lastline =  len(self.data) - 1  # same as number of text lines
+        if index == 'insert':
+            return lastline, len(self.data[lastline]) - 1
+        elif index == 'end':
+            return self._endex(endflag)
+
+        line, char = index.split('.')
+        line = int(line)
+
+        # Out of bounds line becomes first or last ('end') index
+        if line < 1:
+            return 1, 0
+        elif line > lastline:
+            return self._endex(endflag)
+
+        linelength = len(self.data[line])  -1  # position before/at \n
+        if char.endswith(' lineend') or char == 'end':
+            return line, linelength
+            # Tk requires that ignored chars before ' lineend' be valid int
+
+        # Out of bounds char becomes first or last index of line
+        char = int(char)
+        if char < 0:
+            char = 0
+        elif char > linelength:
+            char = linelength
+        return line, char
+
+    def _endex(self, endflag):
+        '''Return position for 'end' or line overflow corresponding to endflag.
+
+       -1: position before terminal \n; for .insert(), .delete
+       0: position after terminal \n; for .get, .delete index 1
+       1: same viewed as begininning of non-existent next line (for .index)
+       '''
+        n = len(self.data)
+        if endflag == 1:
+            return n, 0
+        else:
+            n -= 1
+            return n, len(self.data[n]) + endflag
+
+
+    def insert(self, index, chars):
+        "Insert chars before the character at index."
+
+        if not chars:  # ''.splitlines() is [], not ['']
+            return
+        chars = chars.splitlines(True)
+        if chars[-1][-1] == '\n':
+            chars.append('')
+        line, char = self._decode(index, -1)
+        before = self.data[line][:char]
+        after = self.data[line][char:]
+        self.data[line] = before + chars[0]
+        self.data[line+1:line+1] = chars[1:]
+        self.data[line+len(chars)-1] += after
+
+
+    def get(self, index1, index2=None):
+        "Return slice from index1 to index2 (default is 'index1+1')."
+
+        startline, startchar = self._decode(index1)
+        if index2 is None:
+            endline, endchar = startline, startchar+1
+        else:
+            endline, endchar = self._decode(index2)
+
+        if startline == endline:
+            return self.data[startline][startchar:endchar]
+        else:
+            lines = [self.data[startline][startchar:]]
+            for i in range(startline+1, endline):
+                lines.append(self.data[i])
+            lines.append(self.data[endline][:endchar])
+            return ''.join(lines)
+
+
+    def delete(self, index1, index2=None):
+        '''Delete slice from index1 to index2 (default is 'index1+1').
+
+        Adjust default index2 ('index+1) for line ends.
+        Do not delete the terminal \n at the very end of self.data ([-1][-1]).
+        '''
+        startline, startchar = self._decode(index1, -1)
+        if index2 is None:
+            if startchar < len(self.data[startline])-1:
+                # not deleting \n
+                endline, endchar = startline, startchar+1
+            elif startline < len(self.data) - 1:
+                # deleting non-terminal \n, convert 'index1+1 to start of next line
+                endline, endchar = startline+1, 0
+            else:
+                # do not delete terminal \n if index1 == 'insert'
+               return
+        else:
+            endline, endchar = self._decode(index2, -1)
+            # restricting end position to insert position excludes terminal \n
+
+        if startline == endline and startchar < endchar:
+            self.data[startline] = self.data[startline][:startchar] + \
+                                             self.data[startline][endchar:]
+        elif startline < endline:
+                self.data[startline] = self.data[startline][:startchar] + \
+                                       self.data[endline][endchar:]
+                startline += 1
+                for i in range(startline, endline+1):
+                    del self.data[startline]
+
+    def compare(self, index1, op, index2):
+        line1, char1 = self._decode(index1)
+        line2, char2 = self._decode(index2)
+        if op == '<':
+            return line1 < line2 or line1 == line2 and char1 < char2
+        elif op == '<=':
+            return line1 < line2 or line1 == line2 and char1 <= char2
+        elif op == '>':
+            return line1 > line2 or line1 == line2 and char1 > char2
+        elif op == '>=':
+            return line1 > line2 or line1 == line2 and char1 >= char2
+        elif op == '==':
+            return line1 == line2 and char1 == char2
+        elif op == '!=':
+            return line1 != line2 or  char1 != char2
+        else:
+            raise TclError('''bad comparison operator "%s":'''
+                                  '''must be <, <=, ==, >=, >, or !=''' % op)
+
+    # The following Text methods normally do something and return None.
+    # Whether doing nothing is sufficient for a test will depend on the test.
+
+    def mark_set(self, name, index):
+        "Set mark *name* before the character at index."
+        pass
+
+    def mark_unset(self, *markNames):
+        "Delete all marks in markNames."
+
+    def tag_remove(self, tagName, index1, index2=None):
+        "Remove tag tagName from all characters between index1 and index2."
+        pass
+
+    # The following Text methods affect the graphics screen and return None.
+    # Doing nothing should always be sufficient for tests.
+
+    def scan_dragto(self, x, y):
+        "Adjust the view of the text according to scan_mark"
+
+    def scan_mark(self, x, y):
+        "Remember the current X, Y coordinates."
+
+    def see(self, index):
+        "Scroll screen to make the character at INDEX is visible."
+        pass
+
+    #  The following is a Misc method inheritet by Text.
+    # It should properly go in a Misc mock, but is included here for now.
+
+    def bind(sequence=None, func=None, add=None):
+        "Bind to this widget at event sequence a call to function func."
+        pass