Replace confusing pyproject.toml with backend string in logs

docs/html/reference/build-system/index.md

@@ -17,7 +17,7 @@ setup-py
 ```
 
 <!-- prettier-ignore-start -->
-[`pyproject.toml` based](pyproject-toml)
+[*Backend API* based](pyproject-toml)
 : Standards-backed interface, that has explicit declaration and management of
   build dependencies.
 
@@ -33,36 +33,50 @@ the build system interfaces that pip may use.
 
 ## Determining which build system interface is used
 
-Currently, pip uses the `pyproject.toml` based build system interface, if a
-`pyproject.toml` file exists. If not, the legacy build system interface is used.
-The intention is to switch to using the `pyproject.toml` build system interface
+Currently, pip uses the *backend API* based build system interface, in the
+following scenarios:
+
+- if a `pyproject.toml` file exists, or
+- if {pypi}`setuptools` or {pypi}`wheel` is not installed.
+
+Otherwise, the legacy build system interface is used.
+The intention is to switch to using the *backend API* build system interface
 unconditionally and to drop support for the legacy build system interface at
 some point in the future.
 
 When performing a build, pip will mention which build system interface it is
-using. Typically, this will take the form of a message like:
+using. For the *backend API* based build system interface,
+typically this will take the form of a message like[^2]:
 
 ```none
-Building wheel for pip (pyproject.toml)... done
+Building wheel for pip (<build backend identification>)... done
 ```
 
+[^2]: Here `<build backend identification>` is replaced with the actual value for
+      the given package, e.g. `Building wheel for pip (setuptools.build_meta)... done`
+
+For the `setup.py` based build system interface, typically this will look like
+the following:
+
 ```none
 Building wheel for pip (setup.py)... done
 ```
 
-The content in the brackets, refers to which build system interface is being
-used.
-
 ```{versionchanged} 21.3
 The output uses "pyproject.toml" instead of "PEP 517" to refer to be
-`pyproject.toml` based build system interface.
+*backend API* based build system interface.
+```
+
+```{versionchanged} 23.X
+The output uses the backend specification instead of "pyproject.toml"
+to refer to be *backend API* based build system interface.
 ```
 
 ## Controlling which build system interface is used
 
 The [`--use-pep517`](install_--use-pep517) flag (and corresponding environment
 variable: `PIP_USE_PEP517`) can be used to force all packages to build using
-the `pyproject.toml` based build system interface. There is no way to force
+the *backend API* based build system interface. There is no way to force
 the use of the legacy build system interface.
 
 (controlling-setup_requires)=

docs/html/reference/build-system/pyproject-toml.md

@@ -1,4 +1,4 @@
-# `pyproject.toml`
+# Backend API
 
 ```{versionadded} 10.0
 
@@ -168,3 +168,6 @@ changes and improvements in it.
 - Prior to pip 18.1, build dependencies using `.pth` files are not properly
   supported; as a result namespace packages do not work under Python 3.2 and
   earlier.
+- Starting from version 23.1, pip uses the fallback behaviour of
+  `setuptools.build_meta:__legacy__` when `wheel` or `setuptools` are not
+  installed.

docs/html/reference/build-system/setup-py.md

@@ -1,11 +1,11 @@
 # `setup.py` (legacy)
 
-Prior to the introduction of pyproject.toml-based builds (in {pep}`517` and
+Prior to the introduction of *backend API* based builds (in {pep}`517` and
 {pep}`518`), pip had only supported installing packages using `setup.py` files
 that were built using {pypi}`setuptools`.
 
 The interface documented here is retained currently solely for legacy purposes,
-until the migration to `pyproject.toml`-based builds can be completed.
+until the migration to *backend API* based builds can be completed.
 
 ```{caution}
 The arguments and syntax of the various invocations of `setup.py` made by

news/12346.doc.rst

@@ -0,0 +1 @@
+Avoid referring to "backend API"-based builds as ``pyproject.toml``-based.

news/12346.trivial.rst

@@ -0,0 +1 @@
+Replace confusing ``pyproject.toml`` with backend string in logs.

src/pip/_internal/operations/build/metadata.py

@@ -29,7 +29,9 @@ def generate_metadata(
         # Note that BuildBackendHookCaller implements a fallback for
         # prepare_metadata_for_build_wheel, so we don't have to
         # consider the possibility that this hook doesn't exist.
-        runner = runner_with_spinner_message("Preparing metadata (pyproject.toml)")
+        runner = runner_with_spinner_message(
+            f"Preparing metadata ({backend.build_backend})"
+        )
         with backend.subprocess_runner(runner):
             try:
                 distinfo_dir = backend.prepare_metadata_for_build_wheel(metadata_dir)

src/pip/_internal/operations/build/metadata_editable.py

@@ -30,7 +30,7 @@ def generate_editable_metadata(
         # prepare_metadata_for_build_wheel/editable, so we don't have to
         # consider the possibility that this hook doesn't exist.
         runner = runner_with_spinner_message(
-            "Preparing editable metadata (pyproject.toml)"
+            f"Preparing editable metadata ({backend.build_backend})"
         )
         with backend.subprocess_runner(runner):
             try:

src/pip/_internal/operations/build/wheel.py

@@ -24,7 +24,7 @@ def build_wheel_pep517(
         logger.debug("Destination directory: %s", tempd)
 
         runner = runner_with_spinner_message(
-            f"Building wheel for {name} (pyproject.toml)"
+            f"Building wheel for {name} ({backend.build_backend})"
         )
         with backend.subprocess_runner(runner):
             wheel_name = backend.build_wheel(

src/pip/_internal/operations/build/wheel_editable.py

@@ -24,7 +24,7 @@ def build_wheel_editable(
         logger.debug("Destination directory: %s", tempd)
 
         runner = runner_with_spinner_message(
-            f"Building editable for {name} (pyproject.toml)"
+            f"Building editable for {name} ({backend.build_backend})"
         )
         with backend.subprocess_runner(runner):
             try: