Add meson.build files to build with meson

Provide both build systems in parallel for now, to ensure that we work
out all the differences between the two. Some time from now, we'll give
up on autotools.

Meson tends to be faster and probably easier to read/maintain. On my
machine, the full meson configure+build+install takes a little under
half as long as a similar autotools-based invocation.

Building with meson is a two step process. First, configure the build:

  meson build

Then, compile the project:

  ninja -C build

There's some mild differences in functionality between meson and
autotools.  specifically:

1) No singular update-po target. meson only generates individual
update-po targets for each textdomain (of which we have 3).  To make
this easier, there's a build-aux/update-po script which finds all
update-po targets and runs them.

2) No 'make dist' equivalent. Just run 'git archive' to generate a
suitable tarball for distribution.

4 files changed, 380 insertions, 0 deletions

diff --git a/build-aux/edit-script.sh.in b/build-aux/edit-script.sh.in
new file mode 100644
index 00000000..3e3a1b6a
--- /dev/null
+++ b/build-aux/edit-script.sh.in
@@ -0,0 +1,33 @@
+#!@BASH@
+
+input=$1
+output=$2
+mode=$3
+
+"@SED@" \
+  -e "s|@rootdir[@]|@ROOTDIR@|g" \
+  -e "s|@localedir[@]|@LOCALEDIR@|g" \
+  -e "s|@sysconfdir[@]|@sysconfdir@|g" \
+  -e "s|@localstatedir[@]|@localstatedir@|g" \
+  -e "s|@libmakepkgdir[@]|@LIBMAKEPKGDIR@|g" \
+  -e "s|@pkgdatadir[@]|@PKGDATADIR@|g" \
+  -e "s|@prefix[@]|@PREFIX@|g" \
+  -e "1s|#!/bin/bash|#!@BASH@|g" \
+  -e "s|@PACKAGE_VERSION[@]|@PACKAGE_VERSION@|g" \
+  -e "s|@PACKAGE_NAME[@]|@PACKAGE_NAME@|g" \
+  -e "s|@BUILDSCRIPT[@]|@BUILDSCRIPT@|g" \
+  -e "s|@TEMPLATE_DIR[@]|@TEMPLATE_DIR@|g" \
+  -e "s|@DEBUGSUFFIX[@]|@DEBUGSUFFIX@|g" \
+  -e "s|@INODECMD[@]|@INODECMD@|g" \
+  -e "s|@OWNERCMD[@]|@OWNERCMD@|g" \
+  -e "s|@MODECMD[@]|@MODECMD@|g" \
+  -e "s|@SEDINPLACEFLAGS[@]|@SEDINPLACEFLAGS@|g" \
+  -e "s|@SEDPATH[@]|@SEDPATH@|g" \
+  -e "s|@DUFLAGS[@]|@DUFLAGS@|g" \
+  -e "s|@DUPATH[@]|@DUPATH@|g" \
+  -e "s|@configure_input[@]|Generated from ${output##*/}.sh.in; do not edit by hand.|g" \
+  "$input" >"$output"
+
+if [[ $mode ]]; then
+  chmod "$mode" "$output"
+fi
diff --git a/build-aux/meson-make-symlink.sh b/build-aux/meson-make-symlink.sh
new file mode 100644
index 00000000..501cd43d
--- /dev/null
+++ b/build-aux/meson-make-symlink.sh
@@ -0,0 +1,12 @@
+#!/bin/sh
+set -eu
+
+# this is needed mostly because $DESTDIR is provided as a variable,
+# and we need to create the target directory...
+
+mkdir -vp "$(dirname "${DESTDIR:-}$2")"
+if [ "$(dirname $1)" = . ]; then
+        ln -vfs -T "$1" "${DESTDIR:-}$2"
+else
+        ln -vfs -T --relative "${DESTDIR:-}$1" "${DESTDIR:-}$2"
+fi
diff --git a/build-aux/tap-driver.py b/build-aux/tap-driver.py
new file mode 100644
index 00000000..c231caec
--- /dev/null
+++ b/build-aux/tap-driver.py
@@ -0,0 +1,296 @@
+#!/usr/bin/env python3
+# Adapted from tappy copyright (c) 2016, Matt Layman
+# MIT license
+# https://github.com/python-tap/tappy
+
+import io
+import re
+import subprocess
+import sys
+
+
+class Directive(object):
+    """A representation of a result line directive."""
+
+    skip_pattern = re.compile(
+        r"""^SKIP\S*
+            (?P<whitespace>\s*) # Optional whitespace.
+            (?P<reason>.*)      # Slurp up the rest.""",
+        re.IGNORECASE | re.VERBOSE)
+    todo_pattern = re.compile(
+        r"""^TODO\b             # The directive name
+            (?P<whitespace>\s*) # Immediately following must be whitespace.
+            (?P<reason>.*)      # Slurp up the rest.""",
+        re.IGNORECASE | re.VERBOSE)
+
+    def __init__(self, text):
+        """Initialize the directive by parsing the text.
+        The text is assumed to be everything after a '#\s*' on a result line.
+        """
+        self._text = text
+        self._skip = False
+        self._todo = False
+        self._reason = None
+
+        match = self.skip_pattern.match(text)
+        if match:
+            self._skip = True
+            self._reason = match.group('reason')
+
+        match = self.todo_pattern.match(text)
+        if match:
+            if match.group('whitespace'):
+                self._todo = True
+            else:
+                # Catch the case where the directive has no descriptive text.
+                if match.group('reason') == '':
+                    self._todo = True
+            self._reason = match.group('reason')
+
+    @property
+    def text(self):
+        """Get the entire text."""
+        return self._text
+
+    @property
+    def skip(self):
+        """Check if the directive is a SKIP type."""
+        return self._skip
+
+    @property
+    def todo(self):
+        """Check if the directive is a TODO type."""
+        return self._todo
+
+    @property
+    def reason(self):
+        """Get the reason for the directive."""
+        return self._reason
+
+
+class Parser(object):
+    """A parser for TAP files and lines."""
+
+    # ok and not ok share most of the same characteristics.
+    result_base = r"""
+        \s*                    # Optional whitespace.
+        (?P<number>\d*)        # Optional test number.
+        \s*                    # Optional whitespace.
+        (?P<description>[^#]*) # Optional description before #.
+        \#?                    # Optional directive marker.
+        \s*                    # Optional whitespace.
+        (?P<directive>.*)      # Optional directive text.
+    """
+    ok = re.compile(r'^ok' + result_base, re.VERBOSE)
+    not_ok = re.compile(r'^not\ ok' + result_base, re.VERBOSE)
+    plan = re.compile(r"""
+        ^1..(?P<expected>\d+) # Match the plan details.
+        [^#]*                 # Consume any non-hash character to confirm only
+                              # directives appear with the plan details.
+        \#?                   # Optional directive marker.
+        \s*                   # Optional whitespace.
+        (?P<directive>.*)     # Optional directive text.
+    """, re.VERBOSE)
+    diagnostic = re.compile(r'^#')
+    bail = re.compile(r"""
+        ^Bail\ out!
+        \s*            # Optional whitespace.
+        (?P<reason>.*) # Optional reason.
+    """, re.VERBOSE)
+    version = re.compile(r'^TAP version (?P<version>\d+)$')
+
+    TAP_MINIMUM_DECLARED_VERSION = 13
+
+    def parse(self, fh):
+        """Generate tap.line.Line objects, given a file-like object `fh`.
+        `fh` may be any object that implements both the iterator and
+        context management protocol (i.e. it can be used in both a
+        "with" statement and a "for...in" statement.)
+        Trailing whitespace and newline characters will be automatically
+        stripped from the input lines.
+        """
+        with fh:
+            for line in fh:
+                yield self.parse_line(line.rstrip())
+
+    def parse_line(self, text):
+        """Parse a line into whatever TAP category it belongs."""
+        match = self.ok.match(text)
+        if match:
+            return self._parse_result(True, match)
+
+        match = self.not_ok.match(text)
+        if match:
+            return self._parse_result(False, match)
+
+        if self.diagnostic.match(text):
+            return ('diagnostic', text)
+
+        match = self.plan.match(text)
+        if match:
+            return self._parse_plan(match)
+
+        match = self.bail.match(text)
+        if match:
+            return ('bail', match.group('reason'))
+
+        match = self.version.match(text)
+        if match:
+            return self._parse_version(match)
+
+        return ('unknown',)
+
+    def _parse_plan(self, match):
+        """Parse a matching plan line."""
+        expected_tests = int(match.group('expected'))
+        directive = Directive(match.group('directive'))
+
+        # Only SKIP directives are allowed in the plan.
+        if directive.text and not directive.skip:
+            return ('unknown',)
+
+        return ('plan', expected_tests, directive)
+
+    def _parse_result(self, ok, match):
+        """Parse a matching result line into a result instance."""
+        return ('result', ok, match.group('number'),
+            match.group('description').strip(),
+            Directive(match.group('directive')))
+
+    def _parse_version(self, match):
+        version = int(match.group('version'))
+        if version < self.TAP_MINIMUM_DECLARED_VERSION:
+            raise ValueError('It is an error to explicitly specify '
+                             'any version lower than 13.')
+        return ('version', version)
+
+
+class Rules(object):
+
+    def __init__(self):
+        self._lines_seen = {'plan': [], 'test': 0, 'failed': 0, 'version': []}
+        self._errors = []
+
+    def check(self, final_line_count):
+        """Check the status of all provided data and update the suite."""
+        if self._lines_seen['version']:
+            self._process_version_lines()
+        self._process_plan_lines(final_line_count)
+
+    def check_errors(self):
+        if self._lines_seen['failed'] > 0:
+            self._add_error('Tests failed.')
+        if self._errors:
+            for error in self._errors:
+                print(error)
+            return 1
+        return 0
+
+    def _process_version_lines(self):
+        """Process version line rules."""
+        if len(self._lines_seen['version']) > 1:
+            self._add_error('Multiple version lines appeared.')
+        elif self._lines_seen['version'][0] != 1:
+            self._add_error('The version must be on the first line.')
+
+    def _process_plan_lines(self, final_line_count):
+        """Process plan line rules."""
+        if not self._lines_seen['plan']:
+            self._add_error('Missing a plan.')
+            return
+
+        if len(self._lines_seen['plan']) > 1:
+            self._add_error('Only one plan line is permitted per file.')
+            return
+
+        expected_tests, at_line = self._lines_seen['plan'][0]
+        if not self._plan_on_valid_line(at_line, final_line_count):
+            self._add_error(
+                'A plan must appear at the beginning or end of the file.')
+            return
+
+        if expected_tests != self._lines_seen['test']:
+            self._add_error(
+                'Expected {expected_count} tests '
+                'but only {seen_count} ran.'.format(
+                    expected_count=expected_tests,
+                    seen_count=self._lines_seen['test']))
+
+    def _plan_on_valid_line(self, at_line, final_line_count):
+        """Check if a plan is on a valid line."""
+        # Put the common cases first.
+        if at_line == 1 or at_line == final_line_count:
+            return True
+
+        # The plan may only appear on line 2 if the version is at line 1.
+        after_version = (
+            self._lines_seen['version'] and
+            self._lines_seen['version'][0] == 1 and
+            at_line == 2)
+        if after_version:
+            return True
+
+        return False
+
+    def handle_bail(self, reason):
+        """Handle a bail line."""
+        self._add_error('Bailed: {reason}').format(reason=reason)
+
+    def handle_skipping_plan(self):
+        """Handle a plan that contains a SKIP directive."""
+        sys.exit(77)
+
+    def saw_plan(self, expected_tests, at_line):
+        """Record when a plan line was seen."""
+        self._lines_seen['plan'].append((expected_tests, at_line))
+
+    def saw_test(self, ok):
+        """Record when a test line was seen."""
+        self._lines_seen['test'] += 1
+        if not ok:
+            self._lines_seen['failed'] += 1
+
+    def saw_version_at(self, line_counter):
+        """Record when a version line was seen."""
+        self._lines_seen['version'].append(line_counter)
+
+    def _add_error(self, message):
+        self._errors += [message]
+
+
+if __name__ == '__main__':
+    parser = Parser()
+    rules = Rules()
+
+    try:
+        out = subprocess.check_output(sys.argv[1:], universal_newlines=True)
+    except subprocess.CalledProcessError as e:
+        sys.stdout.write(e.output)
+        raise e
+
+    line_generator = parser.parse(io.StringIO(out))
+    line_counter = 0
+    for line in line_generator:
+        line_counter += 1
+
+        if line[0] == 'unknown':
+            continue
+
+        if line[0] == 'result':
+            rules.saw_test(line[1])
+            print('{okay} {num} {description} {directive}'.format(
+                okay=('' if line[1] else 'not ') + 'ok', num=line[2],
+                description=line[3], directive=line[4].text))
+        elif line[0] == 'plan':
+            if line[2].skip:
+                rules.handle_skipping_plan()
+            rules.saw_plan(line[1], line_counter)
+        elif line[0] == 'bail':
+            rules.handle_bail(line[1])
+        elif line[0] == 'version':
+            rules.saw_version_at(line_counter)
+        elif line[0] == 'diagnostic':
+            print(line[1])
+
+    rules.check(line_counter)
+    sys.exit(rules.check_errors())
diff --git a/build-aux/update-po b/build-aux/update-po
new file mode 100755
index 00000000..ce1ad4be
--- /dev/null
+++ b/build-aux/update-po
@@ -0,0 +1,39 @@
+#!/bin/bash
+
+find_build_directory() {
+  local build_dirs=(*/.ninja_log)
+
+  if [[ ! -e ${build_dirs[0]} ]]; then
+    echo "error: No build directory found. Have you run 'meson build' yet?" >&2
+    return 1
+  elif (( ${#build_dirs[*]} > 1 )); then
+    echo "error: Multiple build directories found. Unable to proceed." >&2
+    return 1
+  fi
+
+  printf '%s\n' "${build_dirs[0]%/*}"
+}
+
+
+filter_targets_by_name() {
+  if command -v jq &>/dev/null; then
+    jq --arg re "$1" -r 'map(.name)[] | select(match($re))'
+  else
+    json_pp | awk -v filter="$1" -F'[:"]' \
+        '$2 == "name" && $(NF - 1) ~ filter { print $(NF - 1) }'
+  fi
+}
+
+# Make things simple and require that we're in the build root rather than
+# trying to chase down the location of this script and the relative build dir.
+if [[ ! -d .git ]]; then
+  echo "This script must be run from the root of the repository" >&2
+  exit 1
+fi
+
+build_dir=$(find_build_directory) || exit 1
+
+mapfile -t targets < \
+    <(meson introspect "$build_dir" --targets | filter_targets_by_name "-update-po$")
+
+ninja -C "$build_dir" "${targets[@]}"