feat(#1045): add same-package-alias lint

src/main/resources/org/eolang/lints/aliases/same-package-alias.xsl

@@ -0,0 +1,41 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+* SPDX-FileCopyrightText: Copyright (c) 2016-2026 Objectionary.com
+* SPDX-License-Identifier: MIT
+-->
+<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:eo="https://www.eolang.org" id="same-package-alias" version="2.0">
+  <xsl:import href="/org/eolang/funcs/lineno.xsl"/>
+  <xsl:import href="/org/eolang/funcs/escape.xsl"/>
+  <xsl:import href="/org/eolang/funcs/defect-context.xsl"/>
+  <xsl:output encoding="UTF-8" method="xml"/>
+  <xsl:template match="/">
+    <defects>
+      <xsl:variable name="pkg" select="/object/metas/meta[head='package'][1]/tail"/>
+      <xsl:for-each select="/object/metas/meta[head='alias' and count(part)=2]">
+        <xsl:variable name="local" select="part[1]"/>
+        <xsl:variable name="fqn" select="replace(part[2], '^Φ\.', '')"/>
+        <xsl:if test="$pkg != '' and $fqn = concat($pkg, '.', $local)">
+          <xsl:element name="defect">
+            <xsl:variable name="line" select="eo:lineno(@line)"/>
+            <xsl:attribute name="line">
+              <xsl:value-of select="$line"/>
+            </xsl:attribute>
+            <xsl:if test="$line = '0'">
+              <xsl:attribute name="context">
+                <xsl:value-of select="eo:defect-context(.)"/>
+              </xsl:attribute>
+            </xsl:if>
+            <xsl:attribute name="severity">
+              <xsl:text>error</xsl:text>
+            </xsl:attribute>
+            <xsl:text>The alias </xsl:text>
+            <xsl:value-of select="eo:escape($fqn)"/>
+            <xsl:text> is redundant, because it refers to an object in the same package (</xsl:text>
+            <xsl:value-of select="eo:escape($pkg)"/>
+            <xsl:text>) as the current file</xsl:text>
+          </xsl:element>
+        </xsl:if>
+      </xsl:for-each>
+    </defects>
+  </xsl:template>
+</xsl:stylesheet>

src/main/resources/org/eolang/motives/aliases/same-package-alias.md

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+# Same-package alias
+
+An `+alias` meta that points to an object in the same package as the
+current file's `+package` meta is redundant. The compiler resolves a
+bare reference to an object of the same package on its own, so such
+an alias only adds noise.
+
+Incorrect:
+
+```eo
++package org.eolang.txt
++alias org.eolang.txt.sprintf
+
+# Foo.
+[x] > foo
+  sprintf x > @
+```
+
+Correct:
+
+```eo
++package org.eolang.txt
+
+# Foo.
+[x] > foo
+  sprintf x > @
+```
+
+An alias that points to a different package, or one that renames the
+object to a new local name, is not redundant and is left alone:
+
+```eo
++package org.eolang.txt
++alias sp org.eolang.txt.sprintf
+
+# Foo.
+[x] > foo
+  sp x > @
+```

src/test/resources/org/eolang/lints/packs/single/same-package-alias/allows-alias-when-no-package-meta.yaml

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+# SPDX-FileCopyrightText: Copyright (c) 2016-2026 Objectionary.com
+# SPDX-License-Identifier: MIT
+---
+sheets:
+  - /org/eolang/lints/aliases/same-package-alias.xsl
+asserts:
+  - /defects[count(defect[@severity='error'])=0]
+input: |
+  +alias org.eolang.txt.sprintf
+
+  [x] > foo
+    sprintf x > @

src/test/resources/org/eolang/lints/packs/single/same-package-alias/allows-cross-package-alias.yaml

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+# SPDX-FileCopyrightText: Copyright (c) 2016-2026 Objectionary.com
+# SPDX-License-Identifier: MIT
+---
+sheets:
+  - /org/eolang/lints/aliases/same-package-alias.xsl
+asserts:
+  - /defects[count(defect[@severity='error'])=0]
+input: |
+  +package org.eolang.txt
+  +alias org.eolang.io.stdout
+
+  [x] > foo
+    stdout x > @

src/test/resources/org/eolang/lints/packs/single/same-package-alias/allows-renamed-same-package-alias.yaml

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+# SPDX-FileCopyrightText: Copyright (c) 2016-2026 Objectionary.com
+# SPDX-License-Identifier: MIT
+---
+sheets:
+  - /org/eolang/lints/aliases/same-package-alias.xsl
+asserts:
+  - /defects[count(defect[@severity='error'])=0]
+input: |
+  +package org.eolang.txt
+  +alias sp org.eolang.txt.sprintf
+
+  [x] > foo
+    sp x > @

src/test/resources/org/eolang/lints/packs/single/same-package-alias/catches-same-package-alias.yaml

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+# SPDX-FileCopyrightText: Copyright (c) 2016-2026 Objectionary.com
+# SPDX-License-Identifier: MIT
+---
+sheets:
+  - /org/eolang/lints/aliases/same-package-alias.xsl
+asserts:
+  - /defects[count(defect[@severity='error'])=1]
+  - /defects/defect[@line='2']
+input: |
+  +package org.eolang.txt
+  +alias org.eolang.txt.sprintf
+
+  [x] > foo
+    sprintf x > @

src/test/resources/org/eolang/lints/packs/single/same-package-alias/prints-context-when-lines-empty.yaml

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+# SPDX-FileCopyrightText: Copyright (c) 2016-2026 Objectionary.com
+# SPDX-License-Identifier: MIT
+---
+sheets:
+  - /org/eolang/lints/aliases/same-package-alias.xsl
+asserts:
+  - /defects[count(defect[@context and @severity='error'])=1]
+document: |
+  <object author="tests">
+    <metas>
+      <meta>
+         <head>package</head>
+         <tail>org.eolang.txt</tail>
+         <part>org.eolang.txt</part>
+      </meta>
+      <meta>
+         <head>alias</head>
+         <tail>sprintf Φ.org.eolang.txt.sprintf</tail>
+         <part>sprintf</part>
+         <part>Φ.org.eolang.txt.sprintf</part>
+      </meta>
+    </metas>
+    <o name="foo"/>
+  </object>