dagparser: parses and formats DAGs as concise text

As discussed during the sprint. See the doc comment and doctests
for specification and examples. This is used in subsequent patches
to export revlog and changelog DAGs, and to generate a repo with
a given changelog DAG.

mercurial/dagparser.py

@@ -0,0 +1,473
+# dagparser.py - parser and generator for concise description of DAGs
+#
+# Copyright 2010 Peter Arrenbrecht <[e-mail]>
+#
+# This software may be used and distributed according to the terms of the
+# GNU General Public License version 2 or any later version.
+
+import re, string
+import util
+
+def parsedag(desc):
+    '''parses a DAG from a concise textual description; generates events
+
+    "+n" is a linear run of n nodes based on the current default parent
+    "." is a single node based on the current default parent
+    "$" resets the default parent to -1 (implied at the start);
+        otherwise the default parent is always the last node created
+    "<p" sets the default parent to the backref p
+    "*p" is a fork at parent p, where p is a backref
+    "*p1/p2/.../pn" is a merge of parents p1..pn, where the pi are backrefs
+    "/p2/.../pn" is a merge of the preceding node and p2..pn
+    ":name" defines a label for the preceding node; labels can be redefined
+    "@text" emits an annotation event for text
+    "!command" emits an action event for the current node
+    "!!my command\n" is like "!", but to the end of the line
+    "#...\n" is a comment up to the end of the line
+
+    Whitespace between the above elements is ignored.
+
+    A backref is either
+     * a number n, which references the node curr-n, where curr is the current
+       node, or
+     * the name of a label you placed earlier using ":name", or
+     * empty to denote the default parent.
+
+    All string valued-elements are either strictly alphanumeric, or must
+    be enclosed in double quotes ("..."), with "\" as escape character.
+
+    Generates sequence of
+
+      ('n', (id, [parentids])) for node creation
+      ('l', (id, labelname)) for labels on nodes
+      ('a', text) for annotations
+      ('c', command) for actions (!)
+      ('C', command) for line actions (!!)
+
+    Examples
+    --------
+
+    Example of a complex graph (output not shown for brevity):
+
+        >>> len(list(parsedag("""
+        ...
+        ... +3         # 3 nodes in linear run
+        ... :forkhere  # a label for the last of the 3 nodes from above
+        ... +5         # 5 more nodes on one branch
+        ... :mergethis # label again
+        ... <forkhere  # set default parent to labelled fork node
+        ... +10        # 10 more nodes on a parallel branch
+        ... @stable    # following nodes will be annotated as "stable"
+        ... +5         # 5 nodes in stable
+        ... !addfile   # custom command; could trigger new file in next node
+        ... +2         # two more nodes
+        ... /mergethis # merge last node with labelled node
+        ... +4         # 4 more nodes descending from merge node
+        ...
+        ... """)))
+        34
+
+    Empty list:
+
+        >>> list(parsedag(""))
+        []
+
+    A simple linear run:
+
+        >>> list(parsedag("+3"))
+        [('n', (0, [-1])), ('n', (1, [0])), ('n', (2, [1]))]
+
+    Some non-standard ways to define such runs:
+
+        >>> list(parsedag("+1+2"))
+        [('n', (0, [-1])), ('n', (1, [0])), ('n', (2, [1]))]
+
+        >>> list(parsedag("+1*1*"))
+        [('n', (0, [-1])), ('n', (1, [0])), ('n', (2, [1]))]
+
+        >>> list(parsedag("*"))
+        [('n', (0, [-1]))]
+
+        >>> list(parsedag("..."))
+        [('n', (0, [-1])), ('n', (1, [0])), ('n', (2, [1]))]
+
+    A fork and a join, using numeric back references:
+
+        >>> list(parsedag("+2*2*/2"))
+        [('n', (0, [-1])), ('n', (1, [0])), ('n', (2, [0])), ('n', (3, [2, 1]))]
+
+        >>> list(parsedag("+2<2+1/2"))
+        [('n', (0, [-1])), ('n', (1, [0])), ('n', (2, [0])), ('n', (3, [2, 1]))]
+
+    Placing a label:
+
+        >>> list(parsedag("+1 :mylabel +1"))
+        [('n', (0, [-1])), ('l', (0, 'mylabel')), ('n', (1, [0]))]
+
+    An empty label (silly, really):
+
+        >>> list(parsedag("+1:+1"))
+        [('n', (0, [-1])), ('l', (0, '')), ('n', (1, [0]))]
+
+    Fork and join, but with labels instead of numeric back references:
+
+        >>> list(parsedag("+1:f +1:p2 *f */p2"))
+        [('n', (0, [-1])), ('l', (0, 'f')), ('n', (1, [0])), ('l', (1, 'p2')),
+         ('n', (2, [0])), ('n', (3, [2, 1]))]
+
+        >>> list(parsedag("+1:f +1:p2 <f +1 /p2"))
+        [('n', (0, [-1])), ('l', (0, 'f')), ('n', (1, [0])), ('l', (1, 'p2')),
+         ('n', (2, [0])), ('n', (3, [2, 1]))]
+
+    Restarting from the root:
+
+        >>> list(parsedag("+1 $ +1"))
+        [('n', (0, [-1])), ('n', (1, [-1]))]
+
+    Annotations, which are meant to introduce sticky state for subsequent nodes:
+
+        >>> list(parsedag("+1 @ann +1"))
+        [('n', (0, [-1])), ('a', 'ann'), ('n', (1, [0]))]
+
+        >>> list(parsedag('+1 @"my annotation" +1'))
+        [('n', (0, [-1])), ('a', 'my annotation'), ('n', (1, [0]))]
+
+    Commands, which are meant to operate on the most recently created node:
+
+        >>> list(parsedag("+1 !cmd +1"))
+        [('n', (0, [-1])), ('c', 'cmd'), ('n', (1, [0]))]
+
+        >>> list(parsedag('+1 !"my command" +1'))
+        [('n', (0, [-1])), ('c', 'my command'), ('n', (1, [0]))]
+
+        >>> list(parsedag('+1 !!my command line\\n +1'))
+        [('n', (0, [-1])), ('C', 'my command line'), ('n', (1, [0]))]
+
+    Comments, which extend to the end of the line:
+
+        >>> list(parsedag('+1 # comment\\n+1'))
+        [('n', (0, [-1])), ('n', (1, [0]))]
+
+    Error:
+
+        >>> try: list(parsedag('+1 bad'))
+        ... except Exception, e: print e
+        invalid character in dag description: bad...
+
+    '''
+    if not desc:
+        return
+
+    wordchars = string.ascii_letters + string.digits
+
+    labels = {}
+    p1 = -1
+    r = 0
+
+    def resolve(ref):
+        if not ref:
+            return p1
+        elif ref[0] in string.digits:
+            return r - int(ref)
+        else:
+            return labels[ref]
+
+    chiter = (c for c in desc)
+
+    def nextch():
+        try:
+            return chiter.next()
+        except StopIteration:
+            return '\0'
+
+    def nextrun(c, allow):
+        s = ''
+        while c in allow:
+            s += c
+            c = nextch()
+        return c, s
+
+    def nextdelimited(c, limit, escape):
+        s = ''
+        while c != limit:
+            if c == escape:
+                c = nextch()
+            s += c
+            c = nextch()
+        return nextch(), s
+
+    def nextstring(c):
+        if c == '"':
+            return nextdelimited(nextch(), '"', '\\')
+        else:
+            return nextrun(c, wordchars)
+
+    c = nextch()
+    while c != '\0':
+        while c in string.whitespace:
+            c = nextch()
+        if c == '.':
+            yield 'n', (r, [p1])
+            p1 = r
+            r += 1
+            c = nextch()
+        elif c == '+':
+            c, digs = nextrun(nextch(), string.digits)
+            n = int(digs)
+            for i in xrange(0, n):
+                yield 'n', (r, [p1])
+                p1 = r
+                r += 1
+        elif c == '*' or c == '/':
+            if c == '*':
+                c = nextch()
+            c, pref = nextstring(c)
+            prefs = [pref]
+            while c == '/':
+                c, pref = nextstring(nextch())
+                prefs.append(pref)
+            ps = [resolve(ref) for ref in prefs]
+            yield 'n', (r, ps)
+            p1 = r
+            r += 1
+        elif c == '<':
+            c, ref = nextstring(nextch())
+            p1 = resolve(ref)
+        elif c == ':':
+            c, name = nextstring(nextch())
+            labels[name] = p1
+            yield 'l', (p1, name)
+        elif c == '@':
+            c, text = nextstring(nextch())
+            yield 'a', text
+        elif c == '!':
+            c = nextch()
+            if c == '!':
+                cmd = ''
+                c = nextch()
+                while c not in '\n\r\0':
+                    cmd += c
+                    c = nextch()
+                yield 'C', cmd
+            else:
+                c, cmd = nextstring(c)
+                yield 'c', cmd
+        elif c == '#':
+            while c not in '\n\r\0':
+                c = nextch()
+        elif c == '$':
+            p1 = -1
+            c = nextch()
+        elif c == '\0':
+            return # in case it was preceded by whitespace
+        else:
+            s = ''
+            i = 0
+            while c != '\0' and i < 10:
+                s += c
+                i += 1
+                c = nextch()
+            raise util.Abort("invalid character in dag description: %s..." % s)
+
+def dagtextlines(events,
+                 addspaces=True,
+                 wraplabels=False,
+                 wrapannotations=False,
+                 wrapcommands=False,
+                 wrapnonlinear=False,
+                 usedots=False,
+                 maxlinewidth=70):
+    '''generates single lines for dagtext()'''
+
+    def wrapstring(text):
+        if re.match("^[0-9a-z]*$", text):
+            return text
+        return '"' + text.replace('\\', '\\\\').replace('"', '\"') + '"'
+
+    def gen():
+        labels = {}
+        run = 0
+        wantr = 0
+        needroot = False
+        for kind, data in events:
+            if kind == 'n':
+                r, ps = data
+
+                # sanity check
+                if r != wantr:
+                    raise util.Abort("Expected id %i, got %i" % (wantr, r))
+                if not ps:
+                    ps = [-1]
+                else:
+                    for p in ps:
+                        if p >= r:
+                            raise util.Abort("Parent id %i is larger than "
+                                             "current id %i" % (p, r))
+                wantr += 1
+
+                # new root?
+                p1 = r - 1
+                if len(ps) == 1 and ps[0] == -1:
+                    if needroot:
+                        if run:
+                            yield '+' + str(run)
+                            run = 0
+                        if wrapnonlinear:
+                            yield '\n'
+                        yield '$'
+                        p1 = -1
+                    else:
+                        needroot = True
+                if len(ps) == 1 and ps[0] == p1:
+                    if usedots:
+                        yield "."
+                    else:
+                        run += 1
+                else:
+                    if run:
+                        yield '+' + str(run)
+                        run = 0
+                    if wrapnonlinear:
+                        yield '\n'
+                    prefs = []
+                    for p in ps:
+                        if p == p1:
+                            prefs.append('')
+                        elif p in labels:
+                            prefs.append(labels[p])
+                        else:
+                            prefs.append(str(r - p))
+                    yield '*' + '/'.join(prefs)
+            else:
+                if run:
+                    yield '+' + str(run)
+                    run = 0
+                if kind == 'l':
+                    rid, name = data
+                    labels[rid] = name
+                    yield ':' + name
+                    if wraplabels:
+                        yield '\n'
+                elif kind == 'c':
+                    yield '!' + wrapstring(data)
+                    if wrapcommands:
+                        yield '\n'
+                elif kind == 'C':
+                    yield '!!' + data
+                    yield '\n'
+                elif kind == 'a':
+                    if wrapannotations:
+                        yield '\n'
+                    yield '@' + wrapstring(data)
+                elif kind == '#':
+                    yield '#' + data
+                    yield '\n'
+                else:
+                    raise util.Abort("invalid event type in dag: "
+                                     + format((type, data)))
+        if run:
+            yield '+' + str(run)
+
+    line = ''
+    for part in gen():
+        if part == '\n':
+            if line:
+                yield line
+                line = ''
+        else:
+            if len(line) + len(part) >= maxlinewidth:
+                yield line
+                line = ''
+            elif addspaces and line and part != '.':
+                line += ' '
+            line += part
+    if line:
+        yield line
+
+def dagtext(dag,
+            addspaces=True,
+            wraplabels=False,
+            wrapannotations=False,
+            wrapcommands=False,
+            wrapnonlinear=False,
+            usedots=False,
+            maxlinewidth=70):
+    '''generates lines of a textual representation for a dag event stream
+
+    events should generate what parsedag() does, so:
+
+      ('n', (id, [parentids])) for node creation
+      ('l', (id, labelname)) for labels on nodes
+      ('a', text) for annotations
+      ('c', text) for commands
+      ('C', text) for line commands ('!!')
+      ('#', text) for comment lines
+
+    Parent nodes must come before child nodes.
+
+    Examples
+    --------
+
+    Linear run:
+
+        >>> dagtext([('n', (0, [-1])), ('n', (1, [0]))])
+        '+2'
+
+    Two roots:
+
+        >>> dagtext([('n', (0, [-1])), ('n', (1, [-1]))])
+        '+1 $ +1'
+
+    Fork and join:
+
+        >>> dagtext([('n', (0, [-1])), ('n', (1, [0])), ('n', (2, [0])),
+        ...          ('n', (3, [2, 1]))])
+        '+2 *2 */2'
+
+    Fork and join with labels:
+
+        >>> dagtext([('n', (0, [-1])), ('l', (0, 'f')), ('n', (1, [0])),
+        ...          ('l', (1, 'p2')), ('n', (2, [0])), ('n', (3, [2, 1]))])
+        '+1 :f +1 :p2 *f */p2'
+
+    Annotations:
+
+        >>> dagtext([('n', (0, [-1])), ('a', 'ann'), ('n', (1, [0]))])
+        '+1 @ann +1'
+
+        >>> dagtext([('n', (0, [-1])), ('a', 'my annotation'), ('n', (1, [0]))])
+        '+1 @"my annotation" +1'
+
+    Commands:
+
+        >>> dagtext([('n', (0, [-1])), ('c', 'cmd'), ('n', (1, [0]))])
+        '+1 !cmd +1'
+
+        >>> dagtext([('n', (0, [-1])), ('c', 'my command'), ('n', (1, [0]))])
+        '+1 !"my command" +1'
+
+        >>> dagtext([('n', (0, [-1])), ('C', 'my command line'), ('n', (1, [0]))])
+        '+1 !!my command line\\n+1'
+
+    Comments:
+
+        >>> dagtext([('n', (0, [-1])), ('#', ' comment'), ('n', (1, [0]))])
+        '+1 # comment\\n+1'
+
+        >>> dagtext([])
+        ''
+
+    Combining parsedag and dagtext:
+
+        >>> dagtext(parsedag('+1 :f +1 :p2 *f */p2'))
+        '+1 :f +1 :p2 *f */p2'
+
+    '''
+    return "\n".join(dagtextlines(dag,
+                                  addspaces,
+                                  wraplabels,
+                                  wrapannotations,
+                                  wrapcommands,
+                                  wrapnonlinear,
+                                  usedots,
+                                  maxlinewidth))

tests/test-doctest.py

@@ -15,5 +15,8 doctest.testmod(mercurial.httprepo)
 import mercurial.util
 doctest.testmod(mercurial.util)
 
+import mercurial.dagparser
+doctest.testmod(mercurial.dagparser)
+
 import hgext.convert.cvsps
 doctest.testmod(hgext.convert.cvsps)