Package ttx-diff as a standalone PyPI package

.github/workflows/python.yml

@@ -0,0 +1,114 @@
+name: ttx-diff CI/CD
+
+on:
+  push:
+    branches:
+      - main
+    paths:
+      - 'ttx_diff/**'
+      - '.github/workflows/python.yml'
+    tags:
+      - 'ttx-diff-v*'
+  pull_request:
+    paths:
+      - 'ttx_diff/**'
+      - '.github/workflows/python.yml'
+  workflow_dispatch:
+
+jobs:
+  test:
+    name: Test Python ${{ matrix.python-version }} on ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macos-latest]
+        python-version: ['3.10', '3.13']
+        # TODO: Re-enable 3.14 once gftools updates pygit2 pin from 1.16.0
+        # https://github.com/googlefonts/gftools/blob/d4c06f5d88e0a849fabf7089d80835a96dc42f30/pyproject.toml#L47-L49
+
+    steps:
+      - uses: actions/checkout@v5
+
+      - name: Set up Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v6
+        with:
+          python-version: ${{ matrix.python-version }}
+
+      - name: Install package with test dependencies
+        working-directory: ttx_diff
+        run: pip install -e ".[test]"
+
+      - name: Run tests
+        working-directory: ttx_diff
+        run: pytest -v
+
+  lint:
+    name: Lint and format check
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v5
+
+      - name: Set up Python
+        uses: actions/setup-python@v6
+        with:
+          python-version: "3.13"
+
+      - name: Check package builds
+        working-directory: ttx_diff
+        run: pipx run build
+
+      - name: Install package with dev dependencies
+        working-directory: ttx_diff
+        run: pip install --find-links=dist 'ttx-diff[dev]'
+
+      - name: Check formatting with ruff
+        working-directory: ttx_diff
+        run: ruff format --check src/ tests/
+
+      - name: Lint with ruff
+        working-directory: ttx_diff
+        run: ruff check src/ tests/
+
+  build:
+    name: Build distribution
+    runs-on: ubuntu-latest
+    needs: [test, lint]
+    if: github.event_name == 'push' && startsWith(github.ref, 'refs/tags/ttx-diff-v')
+
+    steps:
+      - uses: actions/checkout@v5
+
+      - name: Set up Python
+        uses: actions/setup-python@v6
+        with:
+          python-version: "3.x"
+
+      - name: Build package
+        working-directory: ttx_diff
+        run: pipx run build
+
+      - name: Upload artifacts
+        uses: actions/upload-artifact@v4
+        with:
+          path: ttx_diff/dist/
+
+  publish-pypi:
+    name: Publish to PyPI
+    runs-on: ubuntu-latest
+    needs: [build]
+    if: github.event_name == 'push' && startsWith(github.ref, 'refs/tags/ttx-diff-v')
+    permissions:
+      id-token: write  # Required for trusted publishing
+
+    steps:
+      - name: Download artifacts
+        uses: actions/download-artifact@v4
+        with:
+          path: dist/
+
+      - name: Publish to PyPI
+        uses: pypa/gh-action-pypi-publish@release/v1
+        with:
+          packages-dir: dist/

.github/workflows/rust.yml

@@ -1,11 +1,21 @@
 on:
   pull_request:
+    paths-ignore:
+      - 'ttx_diff/**'
+      - '.github/workflows/python.yml'
+      - 'resources/scripts/requirements.in'
+      - 'resources/scripts/requirements.txt'
   merge_group:
   push:
     branches:
       - main
     tags:
       - "*"
+    paths-ignore:
+      - 'ttx_diff/**'
+      - '.github/workflows/python.yml'
+      - 'resources/scripts/requirements.in'
+      - 'resources/scripts/requirements.txt'
 
 name: Continuous integration
 

fontc_crater/src/ci.rs

@@ -209,7 +209,7 @@ fn ttx_diff_has_changes(last_run_sha: &str) -> bool {
         .unwrap();
     std::str::from_utf8(&output.stdout)
         .unwrap()
-        .contains("ttx_diff.py")
+        .contains("ttx_diff/")
 }
 
 #[derive(Debug, Default)]

fontc_crater/src/target.rs

@@ -145,7 +145,7 @@ impl Target {
             Default::default()
         };
         let mut cmd = format!(
-            "python3 resources/scripts/ttx_diff.py '{repo_url}{sha_part}#{}'",
+            "python3 -m ttx_diff '{repo_url}{sha_part}#{}'",
             rel_source_path.display()
         );
         if self.build == BuildType::GfTools {
@@ -371,7 +371,7 @@ mod tests {
         let hmm = target.repro_command("example.com");
         assert_eq!(
             hmm,
-            "python3 resources/scripts/ttx_diff.py 'example.com?123456789a#sources/hi.glyphs'"
+            "python3 -m ttx_diff 'example.com?123456789a#sources/hi.glyphs'"
         );
     }
 }

fontc_crater/src/ttx_diff_runner.rs

@@ -1,12 +1,9 @@
-use std::{
-    collections::BTreeMap,
-    path::{Path, PathBuf},
-    process::Command,
-};
+use std::{collections::BTreeMap, path::PathBuf, process::Command};
 
 use crate::{BuildType, Results, RunResult, Target, ci::ResultsCache};
 
-static SCRIPT_PATH: &str = "./resources/scripts/ttx_diff.py";
+// Run ttx-diff via python -m to ensure we use the venv's installed version
+static TTX_DIFF_MODULE: &str = "ttx_diff";
 
 pub(super) struct TtxContext {
     pub fontc_path: PathBuf,
@@ -24,13 +21,20 @@ pub(super) fn run_ttx_diff(ctx: &TtxContext, target: &Target) -> RunResult<DiffO
     ctx.results_cache
         .copy_cached_files_to_build_dir(target, &build_dir);
     let mut cmd = Command::new("python3");
-    cmd.args([SCRIPT_PATH, "--json", "--compare", compare, "--outdir"])
-        .arg(outdir)
-        .arg("--fontc_path")
-        .arg(&ctx.fontc_path)
-        .arg("--normalizer_path")
-        .arg(&ctx.normalizer_path)
-        .args(["--rebuild", "fontc"]);
+    cmd.args([
+        "-m",
+        TTX_DIFF_MODULE,
+        "--json",
+        "--compare",
+        compare,
+        "--outdir",
+    ])
+    .arg(outdir)
+    .arg("--fontc_path")
+    .arg(&ctx.fontc_path)
+    .arg("--normalizer_path")
+    .arg(&ctx.normalizer_path)
+    .args(["--rebuild", "fontc"]);
     if target.build == BuildType::GfTools {
         cmd.arg("--config")
             .arg(target.config_path(&ctx.source_cache));
@@ -192,30 +196,21 @@ fn non_nan(val: f32) -> f32 {
     if val.is_nan() { 0.0 } else { val }
 }
 
-/// make sure we can find and execute ttx_diff script
+/// make sure we can find and execute ttx-diff module
 pub(super) fn assert_can_run_script() {
     // first check that we can find timeout(1) (not present on macOS by default,
     // install via homebrew)
     assert_has_timeout_coreutil();
-    // then check that we can run the ttx_diff script itself
-    let path = Path::new(SCRIPT_PATH);
-    if !path.exists() {
-        eprintln!(
-            "cannot find script at {}",
-            path.canonicalize().as_deref().unwrap_or(path).display()
-        );
-        std::process::exit(1);
-    }
+    // then check that we can run ttx-diff via python -m
     match Command::new("python3")
-        .arg(SCRIPT_PATH)
-        .arg("--only_check_args")
+        .args(["-m", TTX_DIFF_MODULE, "--only_check_args"])
         .output()
     {
         Ok(output) if output.status.success() => return,
         Ok(output) => {
             let stdout = String::from_utf8_lossy(&output.stdout);
             let stderr = String::from_utf8_lossy(&output.stderr);
-            eprintln!("could not run ttx_diff.py. Have you setup your venv?");
+            eprintln!("could not run ttx-diff. Have you setup your venv?");
             if !stdout.is_empty() {
                 eprintln!("stdout: {stdout}");
             }

resources/scripts/requirements.in

@@ -1,13 +1,10 @@
-absl-py
-# keep fontmake version pinned to ensure output from ttx_diff.py is stable;
+# ttx-diff package with all its dependencies (single source of truth)
+-e file:./ttx_diff
+
+# Pin versions for CI stability (overrides ttx-diff's minimum versions)
+# keep fontmake version pinned to ensure output from ttx-diff is stable;
 # the 'repacker' option enables faster GSUB/GPOS serialization via uharfbuzz
 fontmake[repacker]==3.11.0
-# technically fonttools is in turn a dependency of fontmake but a few of
-# our scripts import it directly, so we list it among the top-level requirements.
-fonttools
-lxml
-cdifflib
-glyphsLib
-# keep gftools pinned as well to ensure ttx_diff.py output is stable.
+# keep gftools pinned as well to ensure ttx-diff output is stable.
 # 0.9.74 is when experimental support for fontc was added to gftools.
 gftools==0.9.93

resources/scripts/requirements.txt

@@ -4,12 +4,14 @@
 #
 #    pip-compile resources/scripts/requirements.in
 #
+-e file:./ttx_diff
+    # via -r resources/scripts/requirements.in
 absl-py==2.3.1
     # via
-    #   -r resources/scripts/requirements.in
     #   gftools
     #   nanoemoji
     #   picosvg
+    #   ttx-diff
 afdko==4.0.2
     # via gftools
 attrs==25.4.0
@@ -41,7 +43,7 @@ cattrs==25.3.0
     #   statmake
     #   ufolib2
 cdifflib==1.2.9
-    # via -r resources/scripts/requirements.in
+    # via ttx-diff
 certifi==2025.10.5
     # via requests
 cffi==2.0.0
@@ -76,6 +78,7 @@ fontmake[json,repacker]==3.11.0
     # via
     #   -r resources/scripts/requirements.in
     #   gftools
+    #   ttx-diff
 fontmath==0.9.4
     # via
     #   afdko
@@ -90,7 +93,6 @@ fontpens==0.2.4
     # via defcon
 fonttools[lxml,repacker,ufo,unicode,woff]==4.60.1
     # via
-    #   -r resources/scripts/requirements.in
     #   afdko
     #   axisregistry
     #   babelfont
@@ -111,6 +113,7 @@ fonttools[lxml,repacker,ufo,unicode,woff]==4.60.1
     #   mutatormath
     #   nanoemoji
     #   statmake
+    #   ttx-diff
     #   ufo2ft
     #   ufolib2
     #   ufomerge
@@ -126,7 +129,9 @@ gflanguages==0.7.7
 gfsubsets==2024.9.25
     # via gftools
 gftools==0.9.93
-    # via -r resources/scripts/requirements.in
+    # via
+    #   -r resources/scripts/requirements.in
+    #   ttx-diff
 gitdb==4.0.12
     # via gitpython
 gitpython==3.1.45
@@ -135,11 +140,11 @@ glyphsets==1.1.0
     # via gftools
 glyphslib==6.12.1
     # via
-    #   -r resources/scripts/requirements.in
     #   bumpfontversion
     #   fontmake
     #   gftools
     #   glyphsets
+    #   ttx-diff
 idna==3.11
     # via requests
 importlib-resources==6.5.2
@@ -148,12 +153,12 @@ jinja2==3.1.6
     # via gftools
 lxml==6.0.2
     # via
-    #   -r resources/scripts/requirements.in
     #   afdko
     #   fontfeatures
     #   fonttools
     #   nanoemoji
     #   picosvg
+    #   ttx-diff
 markdown-it-py==4.0.0
     # via rich
 markupsafe==3.0.3
@@ -177,7 +182,7 @@ openstep-plist==0.5.1
     #   glyphslib
 opentype-sanitizer==9.2.0
     # via gftools
-orjson==3.11.3
+orjson==3.11.4
     # via
     #   babelfont
     #   ufolib2
@@ -220,6 +225,7 @@ pyyaml==6.0.3
     # via
     #   gftools
     #   glyphsets
+    #   ttx-diff
 regex==2025.10.23
     # via nanoemoji
 requests==2.32.5
@@ -232,7 +238,7 @@ resvg-cli==0.44.0
     # via nanoemoji
 rich==14.2.0
     # via gftools
-ruamel-yaml==0.18.15
+ruamel-yaml==0.18.16
     # via gftools
 ruamel-yaml-clib==0.2.14
     # via ruamel-yaml