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diff mercurial/scmutil.py @ 31553:56acc4250900

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scmutil: add a simple key-value file helper The purpose of the added class is to serve purposes like save files of shelve or state files of shelve, rebase and histedit. Keys of these files can be alphanumeric and start with letters, while values must not contain newlines. In light of Mercurial's reluctancy to use Python's json module, this tries to provide a reasonable alternative for a non-nested named data. Comparing to current approach of storing state in plain text files, where semantic meaning of lines of text is only determined by their oreder, simple key-value file allows for reordering lines and thus helps handle optional values. Initial use-case I see for this is obs-shelve's shelve files. Later we can possibly migrate state files to this approach. The test is in a new file beause I did not figure out where to put it within existing test suite. If you give me a better idea, I will gladly follow it.
author Kostia Balytskyi <ikostia@fb.com>
date Fri, 10 Mar 2017 14:33:42 -0800
parents 1fc3d1f02865
children 0f8ba0bc1154
line wrap: on
line diff
--- a/mercurial/scmutil.py	Mon Mar 20 11:50:55 2017 +0900
+++ b/mercurial/scmutil.py	Fri Mar 10 14:33:42 2017 -0800
@@ -965,3 +965,41 @@
     """
     # experimental config: format.generaldelta
     return ui.configbool('format', 'generaldelta', False)
+
+class simplekeyvaluefile(object):
+    """A simple file with key=value lines
+
+    Keys must be alphanumerics and start with a letter, values must not
+    contain '\n' characters"""
+
+    def __init__(self, vfs, path, keys=None):
+        self.vfs = vfs
+        self.path = path
+
+    def read(self):
+        lines = self.vfs.readlines(self.path)
+        try:
+            d = dict(line[:-1].split('=', 1) for line in lines if line)
+        except ValueError as e:
+            raise error.CorruptedState(str(e))
+        return d
+
+    def write(self, data):
+        """Write key=>value mapping to a file
+        data is a dict. Keys must be alphanumerical and start with a letter.
+        Values must not contain newline characters."""
+        lines = []
+        for k, v in data.items():
+            if not k[0].isalpha():
+                e = "keys must start with a letter in a key-value file"
+                raise error.ProgrammingError(e)
+            if not k.isalnum():
+                e = "invalid key name in a simple key-value file"
+                raise error.ProgrammingError(e)
+            if '\n' in v:
+                e = "invalid value in a simple key-value file"
+                raise error.ProgrammingError(e)
+            lines.append("%s=%s\n" % (k, v))
+        with self.vfs(self.path, mode='wb', atomictemp=True) as fp:
+            fp.write(''.join(lines))
+