在为段落添加颜色时，有一个例子中多加了一行。这是我编写环境的方式吗？

Question

\newenvironment我有一个文档，其中我使用改编自的来为各个部分添加颜色这个答案。虽然它似乎在 430 个地方运行良好，但在一个案例中，它通过添加一条额外的线（下图中的 2.）提供了意想不到的结果。

虽然我有办法解决这个问题，但也许有一个解决办法，因为我还有很多文档工作要做，这可能会导致问题的转移。

注意：我也在段落中使用环境，没有问题。例如：Some words \begin{LII}{more words}\end{LII} end of paragraph.

\documentclass[11pt,letterpaper,oneside,onecolumn]{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[margin=1in,showframe]{geometry}
\usepackage{parskip}
\renewcommand\familydefault\sfdefault
\usepackage{xcolor}
\newenvironment{LII}{%% https://tex.stackexchange.com/a/207228/187997
    \leavevmode\color{cyan}\ignorespaces%
}{%
}%
\begin{document}
1. Line before, no color.

(2) Identifier-1 must be defined as an alphanumeric data item such that its value can be a program name.

Line after.

2. Line before, color environment above and below paragraph.

\begin{LII}{%
(2) Identifier-1 must be defined as an alphanumeric data item such that its value can be a program name.
}\end{LII}

Line after.

3. Line before, color environment above and below with \% at end of paragraph.

\begin{LII}{%
(2) Identifier-1 must be defined as an alphanumeric data item such that its value can be a program name.%
}\end{LII}

Line after.

4. Line before, color environment within paragraph.

\begin{LII}{(2) Identifier-1 must be defined as an alphanumeric data item such that its value can be a program name.}\end{LII}

Line after.
\end{document}

Answer 1

如果我添加一个取消跳过，您的示例就可以很好地编译：

\documentclass[11pt,letterpaper,oneside,onecolumn]{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[margin=1in,showframe]{geometry}
\usepackage{parskip}
\renewcommand\familydefault\sfdefault
\usepackage{xcolor}
\newenvironment{LII}{%% https://tex.stackexchange.com/a/207228/187997
    \leavevmode\color{cyan}\ignorespaces%
}{\unskip%
}%
\begin{document}
1. Line before, no color.

(2) Identifier-1 must be defined as an alphanumeric data item such that its value can be a program name.

Line after.

2. Line before, color environment above and below paragraph.

\begin{LII}{%
(2) Identifier-1 must be defined as an alphanumeric data item such that its value can be a program name.
}\end{LII}

Line after.

3. Line before, color environment above and below with \% at end of paragraph.

\begin{LII}{%
(2) Identifier-1 must be defined as an alphanumeric data item such that its value can be a program name.%
}\end{LII}

Line after.

4. Line before, color environment within paragraph.

\begin{LII}{(2) Identifier-1 must be defined as an alphanumeric data item such that its value can be a program name.}\end{LII}

Line after.
\end{document}

Answer 2

\documentclass[11pt,letterpaper,oneside,onecolumn]{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage[margin=1in,showframe]{geometry}
\usepackage{parskip}
\renewcommand\familydefault\sfdefault
\usepackage{xcolor}
\newenvironment{LII}{%% https://tex.stackexchange.com/a/207228/187997
    \par\leavevmode\color{cyan}\ignorespaces%
}{%
    \par
}%
\begin{document}
    1. Line before, no color.
    
    (2) Identifier-1 must be defined as an alphanumeric data item such that its value can be a program name.
    
    Line after.
    
    2. Line before, color environment above and below paragraph.
    
    \begin{LII}{%
            (2) Identifier-1 must be defined as an alphanumeric data item such that its value can be a program name.
    }\end{LII}
    
    Line after.
    
    3. Line before, color environment above and below with \% at end of paragraph.
    
    \begin{LII}{%
            (2) Identifier-1 must be defined as an alphanumeric data item such that its value can be a program name.%
    }\end{LII}
    
    Line after.
    
    4. Line before, color environment within paragraph.
    
    \begin{LII}{(2) Identifier-1 must be defined as an alphanumeric data item such that its value can be a program name.}\end{LII}
    
    Line after.
\end{document}