"Listen" to conda recommendation to use some other solver upon conda install failing; stderr output from "conda install" would be captured and logged

src/datalad_installer.py

@@ -1963,17 +1963,36 @@ def install_package(
         i = 0
         while True:
             try:
-                runcmd(*cmd)
+                result = runcmd(*cmd, stderr=subprocess.PIPE, universal_newlines=True)
+                if result.stderr:
+                    log.error("conda install stderr: %s", result.stderr)
             except subprocess.CalledProcessError as e:
-                if i < 3:
-                    log.error(
-                        "Command failed with exit status %d; sleeping and retrying",
-                        e.returncode,
-                    )
-                    i += 1
-                    sleep(5)
+                log.error(
+                    "Command failed with exit status %d and stderr:\n%s",
+                    e.returncode,
+                    e.stderr,
+                )
+                # Custom workaround for https://github.com/datalad/datalad-installer/issues/206
+                if solver_offered := maybe_offered_solver(e.stderr):
+                    if "--solver" in cmd:
+                        log.info(
+                            "--solver was already in the command, not retrying with offered %s",
+                            solver_offered,
+                        )
+                        # on this type of error, not point of retrying
+                        raise
+                    else:
+                        cmd += ["--solver", solver_offered]
                 else:
-                    raise
+                    if i < 3:
+                        log.error(
+                            "Sleeping and retrying",
+                            e.returncode,
+                        )
+                        i += 1
+                        sleep(5)
+                    else:
+                        raise
             else:
                 break
         binpath = conda.bindir
@@ -2987,6 +3006,33 @@ def parse_links(html: str, base_url: Optional[str] = None) -> list[Link]:
     return links
 
 
+def maybe_offered_solver(e_stderr: Any) -> Optional[str]:
+    # May be would not be needed in the future.
+    solver_offered = None
+    if e_stderr and (
+        solvers_match := re.search(
+            r"CondaValueError: You have chosen a non-default solver backend \(\S*\) .*"
+            "Choose one of: (?P<solvers>.*)",
+            str(e_stderr),
+        )
+    ):
+        solvers_offered = solvers_match.groupdict()["solvers"]
+        solvers_offered = [c.strip() for c in re.split("[ \t,]", solvers_offered)]
+        if len(solvers_offered):
+            solver_offered = solvers_offered[0]
+            if len(solvers_offered) > 1:
+                # TODO: might add a logic in case of multiple to try them one by one
+                log.info(
+                    "More than once choice given (%s), will use the first one.",
+                    solvers_offered,
+                )
+            else:
+                log.info("Will use solver %s", solver_offered)
+        else:
+            log.info("No solver choices offered, continuing as is")
+    return solver_offered
+
+
 @dataclass
 class Link:
     """A hyperlink extracted from an HTML page"""

test/test_install.py

@@ -61,40 +61,30 @@ def test_install_miniconda(tmp_path: Path) -> None:
 
 
 @pytest.mark.miniconda
-def test_install_miniconda_python_match(tmp_path: Path) -> None:
-    miniconda_path = tmp_path / "conda"
-    if sys.version_info[:2] == (3, 7):
-        component = "miniconda=py37_23.1.0-1"
-    else:
-        component = "miniconda"
-    r = main(
-        [
-            "datalad_installer.py",
-            component,
-            "--batch",
-            "--path",
-            str(miniconda_path),
-            "--python-match",
-            "minor",
-        ]
-    )
-    assert r == 0
-    if ON_WINDOWS:
-        pypath = miniconda_path / "python.exe"
-    else:
-        pypath = miniconda_path / "bin" / "python"
-    assert pypath.exists()
-    assert subprocess.run(
-        [str(pypath), "-c", "import sys; print(sys.version_info[:2])"],
-        stdout=subprocess.PIPE,
-        universal_newlines=True,
-        check=True,
-    ).stdout.strip() == repr(sys.version_info[:2])
-
-
-@pytest.mark.skipif(sys.version_info[:2] != (3, 12), reason="Only run on Python 3.12")
-@pytest.mark.miniconda
-def test_install_miniconda_python_match_conda_forge(tmp_path: Path) -> None:
+@pytest.mark.parametrize(
+    "extra_opts,extra_spec",
+    [
+        pytest.param(
+            [], [], marks=pytest.mark.skipif(ON_LINUX, reason="non-Linux only")
+        ),
+        pytest.param(["-c", "conda-forge"], []),
+        # to save testing time we will also bundle with handling of the case when
+        # it might fail to find solver,
+        # ref: https://github.com/datalad/datalad-installer/issues/206
+        pytest.param(
+            [],
+            [
+                "git-annex",
+                "-m",
+                "conda",
+            ],
+            marks=pytest.mark.skipif(not ON_LINUX, reason="Linux only"),
+        ),
+    ],
+)
+def test_install_miniconda_python_match(
+    extra_opts: list[str], extra_spec: list[str], tmp_path: Path
+) -> None:
     miniconda_path = tmp_path / "conda"
     r = main(
         [
@@ -105,9 +95,9 @@ def test_install_miniconda_python_match_conda_forge(tmp_path: Path) -> None:
             str(miniconda_path),
             "--python-match",
             "minor",
-            "-c",
-            "conda-forge",
         ]
+        + extra_opts
+        + extra_spec,
     )
     assert r == 0
     if ON_WINDOWS:
@@ -122,6 +112,10 @@ def test_install_miniconda_python_match_conda_forge(tmp_path: Path) -> None:
         check=True,
     ).stdout.strip() == repr(sys.version_info[:2])
 
+    if extra_spec and extra_spec[0] == "git-annex":
+        # for the git-annex component
+        assert (miniconda_path / "bin" / "git-annex").exists()
+
 
 @pytest.mark.miniconda
 def test_install_miniconda_autogen_path(monkeypatch: pytest.MonkeyPatch) -> None: